RED SNAPPER MANAGEMENT

BarrellBarrell Posts: 999 Officer
REVIEWS
Red snapper management in the Gulf of Mexico:
science- or faith-based?
J. H. Cowan Jr. • C. B. Grimes • W. F. Patterson III • C. J. Walters •
A. C. Jones • W. J. Lindberg • D. J. Sheehy • W. E. Pine III • J. E. Powers •
M. D. Campbell • K. C. Lindeman • S. L. Diamond • R. Hilborn •
H. T. Gibson • K. A. Rose
Received: 12 October 2009 / Accepted: 12 March 2010
The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract The most controversial fishery in U.S.
waters of the Gulf of Mexico (Gulf) is for northern
red snapper Lutjanus campechanus, which collapsed
in the late 1980s when stock biomass became too low
to be fished commercially in the eastern Gulf. Red
snapper management began in 1989; the stock is now
showing signs of recovery. The Gulf of Mexico
Fishery Management Council has been slow to
sufficiently reduce catches of the directed fisheries
to rebuild the stock in a timely fashion, although
compliance with the Magnuson-Stevens Reauthorization
Act of 2006 (MSRA) required substantial cuts
in the harvest of red snapper beginning in 2007. In
our opinion, this could have been avoided if conservative
management practices had been adopted
earlier. We believe that ‘faith-based fisheries’ arguments
have been used to defer effective management
Electronic supplementary material The online version of
this article (doi:10.1007/s11160-010-9165-7) contains
supplementary material, which is available to authorized users.
J. H. Cowan Jr. (&) J. E. Powers
M. D. Campbell K. A. Rose
Department of Oceanography and Coastal Sciences,
Louisiana State University, Baton Rouge, LA, USA
e-mail: [email protected]
C. B. Grimes
Santa Cruz Laboratories, NOAA Fisheries, Southwest
Fisheries Science Center, Santa Cruz, CA, USA
W. F. Patterson III
Department of Biology, University of West Florida,
Pensacola, FL, USA
C. J. Walters
Fisheries Centre, University of British Columbia,
Vancouver, BC, Canada
A. C. Jones
8950 SW 62nd CT, Miami, FL, USA
W. J. Lindberg W. E. Pine III
Department of Fisheries and Aquatic Sciences,
University of Florida, Gainesville, FL, USA
D. J. Sheehy
Aquabio, Inc., Arlington, MA, USA
K. C. Lindeman
Marine and Environmental Systems,
College of Engineering, Florida Institute of Technology,
Melbourne, FL, USA
S. L. Diamond
School of Natural Sciences, University of Western
Sydney, Syndey, NSW, Australia
R. Hilborn
School of Aquatic and Fishery Sciences, University
of Washington, Seattle, WA, USA
H. T. Gibson
North Swell Media, LLC, Jensen Beach, FL, USA
123
Rev Fish Biol Fisheries
DOI 10.1007/s11160-010-9165-7
of red snapper in the Gulf, which in turn has strained
the relationship between science, management, and
stakeholders there. We provide a simple empirical
argument and alternate interpretations of a recently
published perspective on the historical fishery of red
snapper in the Gulf to conclude that the preponderance
of evidence used in the agency stock assessment
process, and the simple arguments made here, do not
support the perspective that the red snapper stock has
increased in size sufficiently to defer compliance with
the MSRA.
Keywords Red snapper Faith-based fisheries
Artificial reefs Overfishing Historical perspective
Introduction
The most controversial fishery in U.S. waters of the
Gulf of Mexico (Gulf) is for northern red snapper
Lutjanus campechanus, which collapsed in the late
1980s when stock biomass became too low to be fished
commercially in almost half of the stock’s former
range. Red snapper management began in earnest in
1989, yet the stock is only now starting to show signs of
recovery. More information about the history of red
snapper management is available elsewhere (e.g.,
Hood et al. 2007), but suffice it to say that conflict
among competing stakeholders has made stock recovery
and sustainable fishing especially difficult to
achieve. Total allowable catch (TAC) has been effectively
split between recreational and commercial
fisheries since the early 1990s, but until recently much
of the fishing mortality was estimated to be attributable
to unintentional harvest (bycatch) of juveniles in the
Gulf shrimp fishery (Goodyear 1995; Porch 2007).
Hence, the Gulf of Mexico Fishery Management
Council has been tugged in many directions, and has
been slow to sufficiently reduce catches of the directed
fisheries to rebuild the stock in a timely fashion.
Recently, compliance with the Magnuson-Stevens
Reauthorization Act of 2006 (MSRA; US Public Law
94–265) has required substantial cuts in the harvest of
red snapper. In our opinion, this could have been
avoided if conservative management practices had
been adopted earlier.
Like the examples described by Hilborn (2006), a
‘faith-based fisheries’ argument has been used to
defer effective management of red snapper, and
consequently has greatly strained the relationships
between science, management, and stakeholders in
the Gulf. The central issues that have stalled timely
management are the beliefs both that bycatch reduction
was possible via gear modifications, and that
deployment of large numbers of artificial reefs in the
northern Gulf transformed and improved habitat for
adult red snapper (Shipp 1999), resulting in larger
standing stocks, that can support higher catch levels
than are currently indicated in red snapper stock
assessments. Assessment results supported the first of
these beliefs, indicating that reduction of bycatch
mortality on juveniles was key to stock recovery, as
did initial positive tests of bycatch reduction devices
(BRDs) that excluded juvenile red snapper and other
finfishes from shrimp trawls. However, observerbased
characterization of BRD performance later
indicated that gear modifications would not reduce
red snapper bycatch sufficiently to ensure a timely
recovery of the red snapper stock (NMFS 2004;
http://www.sefsc.noaa.gov/sedar/download/SEDAR7_
DW38.pdf?id=DOCUMENT). We address the latter
belief—that artificial reef deployment has enhanced
production of red snapper in the northern Gulf and
should be considered the key component of stock
recovery—in this paper.
The belief that mass deployment of artificial reefs,
in their various forms, is a panacea for red snapper
and other overfished stocks in the northern Gulf is
widespread among various fishing constituencies, but
the specifics of this argument were elucidated in a
management perspective published by Shipp and
Bortone (2009). According to these authors, oil and
gas platforms that began appearing in the western
Gulf in the late 1940s function secondarily as large
artificial reefs, and the placement of platforms, as
well as a myriad of other artificial reef structures in
the northcentral and eastern Gulf since the 1970s, has
enhanced production and altered distribution of red
snapper biomass (Shipp and Bortone 2009). True,
results of the last benchmark stock assessment for red
snapper indicate that recruitment and stock productivity
may have increased since the late 1980s.
However, Porch (2007) listed several possible causes
for this putative increase, none of which were
considered by Shipp and Bortone (2009) beyond
artificial reef deployment. Unfortunately, Shipp and
Bortone (2009) provide little information on red
snapper life history or ecology, nor do they provide a
Rev Fish Biol Fisheries
123
mechanistic explanation for the thesis that artificial
reefs have increased red snapper stock-specific productivity,
or a concrete rationale why they believe the
stock is in fact not overfished (despite numerous
stock assessments dating to the 1980s and accompanying
extensive peer review that indicate otherwise).
In the following sections we provide objective
information across multiple topics in support of a
science-based argument that does not support the
faith-based perspective that artificial reefs are responsible
for recent signs that red snapper in the US Gulf
are beginning to recover from overexploitation.
We recognize that the stock assessment process for
red snapper and other species is controversial and
sometimes difficult to understand, so we base our
arguments on two simple vital rates; growth and
mortality (natural and fishing), and how these two
relate in the calculation of biomass production. This
is not a review of red snapper stock assessments, and
neither of these vital rates are taken from assessments;
rather, each is derived empirically. We use
this information to address the following key questions:
(1) it is possible that artificial reefs primarily
attract red snapper to shelter rather than directly
producing more fish (the attraction vs. production
debate), (2) is it likely that habitat for adults limit red
snapper population size?, (3) what is the effect of
fishing on red snapper biomass production?, and (4) is
there evidence that artificial reefs and oil and gas
platforms have increased the carrying capacity for red
snapper in the Gulf such that current management
practices are too stringent? We provide boxes separate
from the text that include procedural details for
readers that wish to see them. We also make
occasional references to values produced by the most
recent red snapper stock assessments (SEDAR 2005;
Porch 2007; SEDAR 2009) for comparisons. Our
analysis does not address spatial variation in demographic
rates due to the intrinsic habitat quality of
essential fish habitat or artificial reefs at scales
smaller than regional (Alabama, Louisiana and
Texas). Instead, it addresses possible habitat effects
at the population level at spatial scales relevant to red
snapper management.
Nor should the information provided here be
perceived as an alternative to the Southeast Data,
Assessment, and Review (SEDAR) process and it’s
outcomes, i.e., this is not a stock assessment. It
should also be noted that the authors of this paper
agree with agency assessment findings that the red
snapper stock is overfished and until recently,
perhaps, experiencing overfishing. Yet, there was
considerable debate among the coauthors about some
of the details in the last assessment (SEDAR 2005), as
well as in the most recent (August 2009) assessment
update. As previously stated, this is not easy work.
Furthermore, this analysis is specific to red
snapper, not a blanket recrimination of artificial reefs
and artificial reef programs. There are clear examples
in the literature where artificial reefs benefit fishes
and ecosystems in which they have been employed,
especially in cases where artificial reefs are used to
mitigate for loss or injury to natural reefs, or to
reduce destructive diving and fishing pressure on
natural reefs (Bortone 1998; Pitcher and Seaman
2000; Claudet and Pelletier 2004; Page et al. 2007,
among others).
The science
The debate about whether artificial habitats attract red
snapper from nearby natural habitats or actually
enhance production of new biomass (i.e., the attraction
vs. production debate) has been called meaningless
and un-resolvable (Shipp 1999; Shipp and
Bortone 2009). This subject often is debated in broad
form for all reef-associated species and, as such, may
be un-resolvable in the broader context. However, it
is more tractable for a single species or life stage,
although still difficult due to the scale and complexity
of needed studies. We believe that red snapper is one
species for which sufficient study has occurred. The
calculations of cohort-specific production are
straightforward and well known (Box 1—See Electronic
Supplementary material, Ricker 1975),
although estimates of some of the vital rates necessary
for the calculations admittedly are difficult to
obtain. For red snapper, growth rates of individual
fish are obtained routinely by using increments
deposited annually in otoliths that provide accurate
age estimates (see review by Fischer 2007), making it
possible to determine schedules of weight-at-age, and
catch-at-age for individuals, and the cohort, respectively,
the latter when rates are averaged over many
individuals sampled over a significant portion of the
stock (Box 1—See Electronic Supplementary material,
Ricker 1975).
Rev Fish Biol Fisheries
123
Red snapper cohort (year class) biomass
and its relationship to growth and mortality
rates, biomass production and year class success
In the following section, we review some basic
concepts explaining how growth and mortality relate
to biomass production and year class success, and
how productivity is a product of these vital rates.
Growth
Growth of red snapper in the Gulf of Mexico has been
well studied (see Fischer 2007 for review). Data in
Fig. 1 are based upon a large, Gulf-wide study funded
by NOAA’s Marine Fisheries Initiative program to
evaluate spatial variability in red snapper population
demographics by collecting and aging more than
1,000 fish from each of three areas (i.e., Alabama,
Louisiana and Texas). Although the oldest fish aged
in this study was 45 years (Fischer et al. 2004), other
reports have documented red snapper ages[50 years
old (Render 1995; Baker et al. 2001; Wilson and
Nieland 2001, ages 54, 53, and 55 years respectively).
These maximum ages are much older than
previously reported, even as recently as the 1980s
(maximum age = 15 years, Nelson and Manooch
1982), and reflect the rapid growth in our knowledge
of red snapper from the 1980s until present.
Growth can be expressed as absolute growth
(length- or weight-at-age) as in Fig. 1, or as instantaneous
or specific growth, which is a rate. Length-atage
in Fig. 1 is depicted in the form of standard
vonBertalanffy growth curves fit to data from each
state individually (Patterson et al. 2001; Fischer et al.
2004) indicating that Louisiana (LA) and Alabama
(AL) fish exhibited similar growth and rates, while
those from Texas (TX; in terms of length-at-age)
were not growing as fast.
What could motivate these growth differences?
Some research suggests that the spatial arrangement
of reefs on the shelf may be contributing to lower
growth (Lindberg et al. 1990; Strelcheck et al. 2005;
Shipley 2008) because of increased competition for
food among residents of closely spaced reefs, and
behavioral interactions between highly gregarious
species (Frazer and Lindberg 1994; Lindberg et al.
2006). The Texas Artificial Reef Program (‘‘rigs to
reefs’’ and ‘‘ships to reef’’, http://www.tpwd.state.tx.us/
landwater/water/habitats/artificial_reef/), unlike LA
and AL which deploys reefs that are spaced more
widely, creates very large reefs out of multiple decommissioned
platforms as well as large sunken
liberty ships placed together in a few locations, often
on or near natural hard bottoms in depths from 20 to
80 m (Campbell 2008). While reefs from both artificial
materials (ships and platforms) are large in size,
Fig. 1 Length-at-age of red
snapper collected from
three locations in the Gulf
of Mexico (from Fischer
et al. 2004). These
relationships are derived
from the same samples used
in Fig. 2
Rev Fish Biol Fisheries
123
decommissioned platforms are usually more complex
than the gutted hulls of ships, further complicating
direct comparisons of fish population responses
between reef type and spatial location. Unfortunately,
it is impossible to provide a more detailed comparison
of the effects on red snapper of artificial reefs
across a range of reef size and complexity because
there is no record of the types and configurations of
reefs deployed off Alabama, as the state does not
require reefs builders to report such specifics despite
the fact that more than 4,500 km2 of the Alabama
shelf has been set aside for artificial reef deployment.
That said, the role of Gulf oil and gas platforms as
fish habitat, including red snapper, has recently been
reviewed (VERSAR 2009), and these large structures
appear to function quite differently from small, relatively
low relief artificial reefs typical of those
deployed off Alabama and the Florida panhandle.
Red snapper harvested on the west Florida shelf are
mostly associated with natural habitats.
We calculated the mean weight of red snapper
from ages 30 to 50 years old ðX ¼ 10;147 gÞ; mean
age of these fish is 37 years (from the data used in
Fig. 1). Assuming that red snapper recruit to artificial
and natural reefs at or near age 2 (Patterson et al.
2001), the estimated instantaneous growth rate from
ages 2 to 37 years is G = 0.06 year-1 (Box 1—See
Electronic Supplementary material) based upon a
mean weight at age 2 of 1,049 g (mean weight of 964
age-2 red snapper collected from LA, AL, and TX in
almost equal numbers). However, because growth
rate is age-dependent, we also estimated growth rates
from ages 2 to 6, 6 to 10, and 10 to 37. These rates are
G = 0.42 year-1, 0.09 year-1 and \0.01 year-1,
respectively, ignoring the geographic variability
shown in Fig. 1. It is also important to recognize
that in general, growth rate scales to mortality rate in
nature (i.e., younger fishes may be growing faster but
they also die faster; Houde 1996).
Mortality
The instantaneous rate of total mortality (Z) is
commonly estimated from catch curves (plots of
frequency-at-age) of adults after entry into the fishery,
i.e., as the slope of the regression of the descending
limb of the plot of the loge frequency on age (Ricker
1975). Figure 2 shows this decline well for red
snapper, with many fish being captured prior to
reaching size of full vulnerability to fishing (age 1.5–
2 years), after which catch-at-age declines steeply.
Data used in Fig. 2 were obtained by collecting
samples ([1,000 fish in each area) at commercial
and recreational ports of call Gulf-wide (i.e., AL-west
Florida (FL), LA and TX), and results are similar to
those from other studies in the US Gulf (Fischer 2007).
Instantaneous total mortality rate (Z) is then often
partitioned into natural (M) and fishing mortality (F)
components such that Z is assumed to be the sum of
the component parts of F and M. In the absence of
bycatch mortality, Z = M (Box 2—See Electronic
Supplementary material) until fish grow large enough
to become vulnerable to fishing. For fish populations,
it has been demonstrated that M generally is sizeand/
or age-specific; younger, smaller fishes have
higher rates that decline and stabilize sometime
during the first year of life (Houde 1996; Lorenzen
1996).
From a life history perspective, fish like red
snapper are bet-hedgers in that a single female will
Fig. 2 Age-frequency
distribution of red snapper
catches from three locations
in the Gulf of Mexico
(from Fischer et al. 2004)
Rev Fish Biol Fisheries
123
produce millions of very small eggs over her considerable
lifetime (Jackson et al. 2007), with each egg
having a very small chance of survival to adulthood
(\0.1%; Fuiman 2002); in most years any given
female may not produce a single survivor. Bet-hedgers
solve this problem by investing minimal energy into
developing each egg; large batches of eggs are freely
broadcast into the water column with no parental care.
Longevity coupled with high fecundity, and protracted
spawning seasons provide many chances for a population
to produce an occasional strong year class
(Winemiller and Rose 1992, 1993; Houde 2008). Red
snapper in nature may only need to produce a strong
year class every 5–10 years to keep the population
stable, able to sustain a reasonable harvest, and
evidence suggests that even in good years relatively
few females contribute to a given year class (Gold and
Saillant 2007). Apparently red snapper have the
reproductive capacity and potential to significantly
capitalize when opportunities for favorable reproductive
success exist. For example, estimates of relative
year class strength over a 20-year period show several
dominant year classes (1989, 1995, 2004, 2006), while
during this same period the magnitude of the indices
varies by a factor of four with no evident trend in
recruitment (Allman and Fitzhugh 2007; SEDAR
2009). The absence of trend over this 20-year period
does not support the view that long-term improvement
(or deterioration) in habitat or environmental conditions
are operating stock-wide.
Rates of M are difficult to estimate, especially
during early life, because mortality is rarely observed
and estimation typically requires successive samples
from a single cohort (year class) over time. For
species with life history strategies similar to that of
red snapper, M rates are highest while eggs and larvae
are planktonic (Houde and Zastrow 1993), i.e., about
20% per day for larvae of marine shelf species, with
rates even higher still for eggs. High mortality rates
of eggs and larvae lead to rapid declines in cohort
biomass of most marine fishes over the first few days
or weeks (Houde 1989a, b; Winemiller and Rose
1992, 1993). This period of rapid decline in biomass
is evidenced as the period in life where cohortspecific
G is less than cohort-specific M and is a
critical time for determining the number of fish that
transition to early juveniles. Once small juveniles
settle to the bottom, there appears to be a spike in
rates immediately after settlement for many species
(see Able et al. 2006 for review), followed by rapid
decline in rates thereafter. While no estimates of
mortality rates for planktonic red snapper exist,
recent work on young juveniles show that Ms of
age-0 snapper are high (M = 0.98–3.7 year-1) during
and following settlement on sand and mud
substrates, and may increase when the density of
red snapper recruits increases (Rooker et al. 2004;
Szedlmayer 2007; Brooks and Powers 2007; Wells
et al. 2008b; Gazey et al. 2008; Gallaway et al. 2009;
SEDAR 2009; M = 2.0 year-1 was used for model
projections in the 2009 red snapper assessment
update). At some point cohort biomass ceases to
decline, when increasing biomass via growth is
equivalent to biomass lost via mortality (G = M). It
is before and during this time that course control of
year class success is likely exercised because only
small differences in M during the period when
mortality rates are at their highest can cause order
of magnitude variation in the number of survivors to
later life stages (Houde 1987, 1989a, b, 2008). Once
past the life stage where G = M, a cohort or year
class will increase in biomass (G[M) to a point
later in life where G = M again, followed by another
period where G\M when cohort biomass again
declines as old members of the cohort grow slowly
and die. Red snapper most certainly follow this same
pattern and year class success is likely determined for
red snapper by subtle changes in M during the first
year of life before they recruit to artificial reefs
(Strelcheck et al. 2005; Wells et al. 2008b; Gazey
et al. 2008), which is entirely consistent with what is
known about other fishes with similar life-history
strategies (Houde 1987, 1989a, b, 1996, 2008).
Natural mortality rates of sub-adult and adult red
snapper after they have recruited to structured habitat
also are difficult to estimate, because sampling of a
cohort (year class) through time in the absence of
fishing is now impossible. Many other stocks suffer
from this same problem; thus numerous methods
have been developed to estimate M objectively for
adult fishes from exploited populations, many of
which are based upon longevity (Box 2—See Electronic
Supplementary material). Solving these equations
for M in Box 2—See Electronic Supplementary
material for Tmax = 54 year provides estimates of
0.08 year-1–0.11 year-1, respectively.
Whether or not M is 0.08 year-1 or 0.11 year-1
based upon the methods in Box 2—See Electronic
Rev Fish Biol Fisheries
123
Supplementary material, or 0.10 year-1 as used in the
most recent agency benchmark assessment (SEDAR
2005), it illustrates the point that biomass of a red
snapper cohort (year class) after age 1 is likely to
increase only during a few years when G[M;
afterward growth rate slows and biomass begins to
decline (G\M) because mean G year-1 for red
snapper between ages 10 and 37 is low (\0.01 year-1).
For many species, the point at which cohort-specific
biomass begins to decline later in life is related to a
shift in the amount of energy (a function of food
consumed) that sexually mature adults devote to
somatic (body) growth compared gonadic growth
(production of spawning products) i.e., eggs in the
case of females. Thus, it is likely that G becomes
less than M for red snapper before or around the
age that full reproductive potential is reached (age
14–15 years; Fig. 3), which stresses both the importance
and challenges of rebuilding age structure in
the Gulf red snapper population.
Reproductive potential lost as biomass as the
cohort grows older is offset for many years by
increased egg production in older spawners because
these larger females produce more eggs (Campbell
2008; Walters et al. 2008a; Venturelli et al. 2009).
This also implies that fishing pressure on red snapper
by the directed fishery is highest during the time
when biomass production is highest and continues,
but to a lesser degree on older age classes that are
responsible for most of the egg production.
Does available habitat for age 11 and older red
snapper limit population size?
Given the information on G and M above, the premise
that year class success in red snapper is not
determined until fish are between 1.5 and 2 years
old, or at the time when they largely begin to inhabit
reefs as sub-adults, is inconsistent with a periodic, or
bet-hedging, life history strategy (Winemiller and
Rose 1992, 1993). For example, there is a longstanding
debate among reef researchers about what
limits population size: (1) the supply of new recruits
from the plankton; or (2) the availability of habitat for
newly settled recruits. As we have demonstrated
above, fish, including reef fish, are most abundant
when they are young. Some believe that the availability
of interstices (i.e., small hiding spots) for
newly settled post-larvae and juveniles can be
limiting; those individuals not finding refuge suffer
higher predation rates. In this case, mortality is
thought to be density-dependent (Forrester 1990;
Holbrook et al. 2000; Forrester and Steele 2000,
2004). It should be noted, however, that age-0 red
snapper rarely recruit directly to high-relief natural or
artificial reefs, rather they settle on sand/mud substrates
and transition to more structured habitat with
size and age (Patterson 1999; Patterson et al. 2005;
Wells et al. 2008a, b; Gallaway et al. 2009). It is this
transition that makes them vulnerable to shrimp
trawling.
Others believe that the supply of reef fish larvae is
limiting, with good year classes being determined by
density-independent factors that occur while larvae
are in plankton prior to settlement on the reef
(Doherty and Williams 1988; Doherty and Fowler
1994a, b; Milicich and Doherty 1994; Booth et al.
2000; Sale 1991, 2002). In neither of the above
scenarios is habitat for adults limiting; many studies
have shown that adult fishes usually do not saturate
reefs, especially in exploited populations (Doherty
and Williams 1988; Doherty and Fowler 1994a, b;
Booth et al. 2000). In nature, however, it is unlikely
to be a simple dichotomy, as more than one factor can
be limiting at different life stages (multiple causalities).
Other post-settlement factors can significantly
Fig. 3 Red snapper relative cohort biomass estimated from
survivorship (survivors per recruit; F = 0) to age and mean
body weight at age, which was estimated from vonBertalanffy
growth parameters (K = 0.18) reported in SEDAR (2005).
Annual survival rate was estimated by assuming that natural
mortality rate M is inversely proportional to body length
(Lorenzen survival model, Lorenzen 2000), dropping to an
asymptotic adult M of 0.08
Rev Fish Biol Fisheries
123
modify recruitment patterns and year class success,
and it is conceivable that availability of adult habitat
can been limiting for species that require specific
substrates to complete their life cycle (Winemiller
and Rose 1992).
The availability of low-relief, natural habitat for
post-settlement red snapper (ages 0 and 1) has been
suggested to be limiting (Gallaway et al. 2009)
because the numbers of age 0 and 1 red snapper have
been poorly correlated, suggesting that densitydependent
mortality is occurring sometime early in
the second year of life. However, age-1 red snapper
are considerably more vulnerable to shrimp trawls
than age-0s because of mesh sizes used by shrimp
trawlers (Gallaway and Cole 1999), making it
difficult to draw strong inference about the role of
low-relief natural habitat and its availability (see
below) in the shallow Gulf as it relates to the numbers
of juveniles that ultimately recruit to higher relief
natural and artificial reefs.
We argue that the amount of habitat for an adult
bet-hedger like red snapper, especially artificial
habitats that account for \5% (Stanley and Wilson
2003) of total useable habitat as compared to suitable
natural habitats, probably does not limit recruitment
or population size. The useable habitat increase due
to artificial habitats is likely less even than the 5%
reported above because this estimate includes all oil
and gas platforms, many of which are not suitable
habitat for red snapper, especially the inshore to midshelf
platforms in the northwestern Gulf that are
subjected to Mississippi River discharge.
Oil and gas platforms, that began appearing in the
western Gulf in the late 1940s, function secondarily
as large artificial reefs (Shipp and Bortone 2009).
However, platforms bear little resemblance to either
natural reefs or most artificial reef materials intentionally
placed to promote fisheries, and it is possible
that artificial reefs primarily attract fish to shelter
rather than directly producing more fish. From a life
history perspective, even if artificial reefs have
increased carrying capacity, but not the intrinsic rate
of population growth, and the stock is still at low
abundance, adding habitat would not have had any
significant positive impact on stock biomass. Nor
would it increase the over fishing level (OFL) as a
proportion of biomass, rather it would only increase
the potential yield. This is true unless artificial reefs
provide habitat of substantially higher quality than
existing natural reefs. Furthermore, the attraction of a
diverse suite of predators (e.g., jacks, mackerels,
groupers, sharks, cobia, bluefish, other snappers, etc.;
VERSAR 2009) by deploying artificial reefs into
shallower red snapper nursery habitats, where population
size is much more likely to be regulated (Wells
et al. 2008b; Gazey et al. 2008), could actually have a
negative impact on stock productivity by increasing
predation (Hixon and Beets 1993; Hixon and Webster
2002; Walters et al. 2008b). Therefore, we infer that
red snapper life history is inconsistent with the notion
that habitat limitation (Gallaway et al. 2009; Shipp
and Bortone 2009) is a strong actor in regulating
population size in this species.
Fishing and its effect on production
The process to assess the status of the red snapper
stock is complex and is discussed only briefly here. To
begin, a wide array of biological data is collected and
summarized. Detailed information on all biological
data is available in the 2005 red snapper assessment
(SEDAR 2005) and the 2009 assessment update
(SEDAR 2009). Biological data included are primarily
on age structure of the landed catch, age at first
spawning, fecundity, ratio of males to females, M, Z,
G, and spawning behavior. Fishery dependent data
required includes types of fishers (commercial versus
recreational), fishing gear (longlines, rod and reel,
trawls, etc.), landings by each gear and fisher, the
fishing effort by fisher type, and information on size
and age of fish harvested by each gear. Fishery specific
information is also considered such as the effect of
regulatory actions on landings (which change through
time and alter fishery observed size/age structure of
catch), vulnerability schedules to different gear types
by fish size, discard rates (release rate of undersized
fish), and discard mortality rates (proportion of these
released fish that die), and the time and geographic
location of the catches. Also in the assessment,
geographical boundaries of different stocks or populations
are defined. From the combined biological and
fisheries data, the current status and condition of the
stock is defined and predictions are made about how it
will respond to varying levels of F.
Recall the importance of the ratio G:M in the
production equations found in Box 1—See Electronic
Supplementary material (i.e., when G[M cohort
Rev Fish Biol Fisheries
123
biomass increases, when G\M cohort biomass
declines, and the age-frequency data shown in
Fig. 2). Additionally, recall that Z is the sum of its
component parts F and M. If we estimate the rate of
decline from the age data in Fig. 2, the slope of the
descending arm is about 47% per year (apparent total
instantaneous mortality Z ¼ 0:63 year1 for LA, AL
and TX combined) which is consistent with Gitschlag
et al. (2005) estimate (0.54 year-1) for red snapper
sampled from explosively-removed petroleum platforms
in the north western Gulf, as well as an estimate
derived from data reported by Szedlmayer (2007)
from fish sampled off Alabama using Gitschlag et al.
(2005) catch curve methodology (0.82 year-1).
Assuming that M for red snapper aged 2 years and
older is 0.10 year-1, the difference is attributable both
to fishing and, since 1990, to a decline in vulnerability
of older red snapper to fishing.
As such, biomass production of an exploited
population is based upon Z, which is the sum of
F ? M. In the most recent red snapper benchmark
assessment (SEDAR 2005), estimated F at ages 2–6
and 2–10 averaged 0.74 and 0.59 year-1, respectively.
If our goal is to keep the ratio G:Z near 1, i.e.,
to keep biomass constant through time, these Fs are
too high and the ratio now is\1.00 even for ages 2–6
when fish are growing rapidly (given a G of
0.42 year-1). Consequently, it is possible for biomass
to decline even when red snapper Gs are high because
the Z exceeds this estimated growth rate. As in most
assessments, estimates of F in the most recent red
snapper assessment are somewhat uncertain; however,
these errors would have to have been very large,
and F estimates biased very high, for the stock
actually to have been experiencing positive population
growth prior to the recent regulatory reductions
in fishing mortality.
The relationship between G and M, and their
importance to production explains why fishing has
been shown to be a significant source of uncertainty
about whether artificial reefs are capable of producing
new fish biomass (Powers et al. 2003). This
uncertainty is attributable to the role that fishing plays
in density-dependent population regulation (Shepherd
and Cushing 1980; Myers 1995; Lorenzen and
Enberg 2002), and whether F ? M is sufficiently
high to override natural population regulators such as
habitat limitation. To add perspective, a recent ICES
Working Group on Ecosystem Effects of Fishing
Activities (ICES 2009) made recommendations concerning
the likely rates of sustainable removal rate of
fishes with life histories similar to that of red snapper,
but for which formal stock assessments are unavailable.
They recommended following an approach
using the natural mortality rate for species to place
a maximum bound on an allowable F, i.e., the F = M
strategy (see Clark 1991; Garcı´a et al. 2008), and
using maximum age (Tmax) to estimate M if possible.
Two different lines of support were provided for an
F = M strategy for relatively long-lived and latematuring
species. The first rationale is that doubling
mortality on long-lived species (if F = M then
Z = 2 9 M) might be near the limit of their ability
to compensate for increased mortality through density-
dependent increases in productivity (Myers and
Mertz 1998; Walters and Martell 2004; Garcı´a et al.
2008). The second is that many long-lived species
that have been targeted in fisheries have undergone
major declines in abundance when F exceeded M
(Musick 1999; Heifetz et al. 2007; Love et al. 2005).
There is additional empirical evidence in support of
our conclusion that red snapper remain overfished.
Fischer (2007) provides a review of vonBertalanffy
growth parameters (K) from studies of red snapper in
the Gulf. Growth parameter estimates (Ks) from
Fischer et al. (2004) are inversely correlated to
estimates of effective population size (i.e., the number
of females contributing to any given year class) by
region provided by Gold and Saillant (2007). The
highest Ks were derived from the regions with the
lowest effective population size (AL and TX). Moreover,
red snapper off Alabama are juvenescent and
maturing at earlier ages than normal (Jackson et al.
2007), and red snapper collected more recently by
Nieland et al. (2007) off Louisiana appear to be
reaching smaller size-at-age. Juvenescence in fish
population occurs when Z on adults is high, and fishers
selectively remove larger, faster growing, late maturing
individuals more rapidly because these fish are the
first to become vulnerable to fishing (Trippel 1995;
Trippel et al. 1997; Murawski et al. 2001). As such,
per capita food resources increase for individuals that
remain; some of these individuals respond by maturing
at earlier ages. Those that that are genetically
predisposed to mature earlier then have a selective
advantage under fishing pressure and a greater chance
of contributing spawning products over late-maturing
individuals. This ultimately leads to directional
Rev Fish Biol Fisheries
123
selection for early maturing females in the population
(Rijnsdorp 1993; Kraak 2007; Law 2007 and papers in
theme session entitled Disentangling the causes of
maturation trends in exploited fish populations, Mar
Ecol Prog Ser. 335 (2007)). Both of these phenomena
are well-documented symptoms of overexploitation
that would not be evident at recent annual harvest
levels (9.12 million lbs) if stock size and carrying
capacity in the Gulf had dramatically increased.
The faith
The role of artificial reefs in the management (policy),
population dynamics and status of red snapper in the
Gulf has been controversial. The scientific community
and fishers have debated this issue many times over.
We recognize that oil and gas platforms and artificial
reefs (collectively ARs) are associated with successful
recreational and commercial fisheries, and some have
argued that the Gulf red snapper stock has been
enhanced by the addition of structure as habitat for
adults (Shipp and Bortone 2009). So we return full
circle to the attraction versus production (AvP) debate.
When examined relative to earlier AvP conceptual
models (Bohnsack 1989; Lindberg et al. 1990; Grossman
et al. 1997; Powers et al. 2003), and as we
describe it in this paper, a case for AR enhancement of
red snapper production is highly doubtful. As we have
pointed out, it is possible that ARs have increased the
vulnerability of red snapper to fishing by aggregating
fish closer to shore, and perhaps have increased
predation mortality by attracting piscivores into nursery
areas for juveniles (Cowan et al. 1999). We also
know that fishing mortality for red snapper is quite
high (SEDAR 2005, 2009) and that much of this
fishing (from the recreational sector) occurs over ARs.
It has been shown that red snapper gain little nutrition
from ARs, moving large distances away from structured
habitat each day to forage on the benthos (see
review by McCawley and Cowan 2007; McDonough
2008). This also is true of juvenile and adult red
snapper found on natural reefs (Wells et al. 2008a).
Site fidelity to ARs by red snapper is moderate to low
(see Patterson 2007 for review; Diamond et al. 2007;
Westmeyer et al. 2007; McDonough 2008), and
residence around standing platforms with high vertical
relief may cause a significant increase in vulnerability
to predation because of the large numbers of piscivores
frequenting these anomalous structures when compared
to natural habitats in the Gulf (VERSAR 2009).
This situation is exacerbated by barotrauma that makes
red snapper regulatory discards less able to avoid
predators after fish are released (Campbell 2008).
Even when comparing the findings from works
referenced above with other results of studies of red
snapper diet (Szedlmayer and Lee 2004; Ouzts and
Szedlmayer 2003) and site fidelity (Szedlmayer and
Shipp 1994; Schroepfer and Szedlmayer 2006), the
differences in reported results appear to be more
dependent upon dispute about prey habitat affinities,
and how site fidelity is defined than significant
differences in results among studies.
The argument that ARs have increased red snapper
stock size appears to be based upon two key
observations. First is the observation that landings
of red snapper increased in the eastern Gulf concurrently
with large numbers of ARs deployed in this
area beginning in 1986. Second, there has been a shift
in overall landings from the eastern to western Gulf
in concert with the arrival of large numbers oil and
gas platforms off Louisiana beginning in 1947 (Shipp
and Bortone 2009). These changes are well supported
by data (Porch et al. 2007) and we do not deny they
occurred. Where we disagree is in their interpretation.
For example, there is a positive correlation between
red snapper landings in the eastern Gulf and the
establishment of the 4,500 km2 Artificial Reef Permit
Zone off AL, which began in 1986 with the creation
of the Hugh Swingle Permit Area. This occurred just
prior to the realization that red snapper management
in the Gulf was necessary to reduce the risk of further
stock collapse. Since 1986, many ARs have been
deployed in this area (10 s of 1,000 s; Patterson
1999; Bailey et al. 2001) and red snapper catches
from the permit area have gone up as the number of
reefs (and fishing effort) increased. This relationship
has been cited as evidence of the beneficial effects of
ARs on the red snapper population in the Gulf (Shipp
1999).
However, we contend that this is a spurious
relationship created by knowledge and law, i.e., the
curious juxtaposition of new scientific knowledge
about red snapper and fortuitous changes in statutes
governing fisheries management. When red snapper
management began in the late 1980s, the fishery had
existed for about 100 years (Moe 1963; Camber 1955
reviewed in Porch et al. 2007), red snapper catches
Rev Fish Biol Fisheries
123
had declined Gulf-wide, and the commercial fishery
had been largely extirpated from the eastern Gulf.
Early management regulations targeted both the
commercial and recreational sectors of the fishery
by establishing a TAC of 3 million lbs annually for
the commercial fishery, and implementation of
restrictive bag limits for the recreational fishery
(Hood et al. 2007). Additionally, management agencies
identified the potential issue of juvenile red
snapper bycatch in the shrimp fishery and the role of
reducing bycatch to aid in stock recovery (Goodyear
1995). At that time, bycatch reductions of 40–50%
were believed to be necessary to recover red snapper,
in addition to reductions in harvest of adults (Goodyear
1995). This two-pronged management (and
policy) approach of curtailing harvest of adults and
reducing juvenile bycatch to increase recruitment has
been the primary recovery formula for red snapper
ever since (Hood et al. 2007).
This management approach also stimulated substantial
research into all aspects of red snapper
population ecology. Outcomes from this research
have greatly expanded our knowledge of red snapper
and motivated revisions to key life-history parameters
used in stock assessments. For example, new and
improved methods of aging and age verification of
red snapper using increments in otoliths have become
much more widely applied as has collection efforts
for representative age samples. What followed from
these efforts was a progression of red snapper age
estimates that extended estimated longevity from
15 years in the early 1980s (Nelson and Manooch
1982) to 55 years, as we know today (Fischer 2007
for review). As shown earlier, estimates of maximum
age are commonly used in simple equations to
estimate M and to serve as a reference point from
which to compare exploitation levels F. Thus changes
in maximum age can lead to large changes in M and
in turn assessments of the relative magnitude of F.
In 1996, the Magnuson-Stevens Act of 1976
(MSA; U.S. Public Law 94–265) was reauthorized
and revised as the Sustainable Fisheries Act (SFA;
U.S. U.S. Public Law 104–297), which contained
stricter conservation standards than the MSA (e.g.,
definitions of overfished and overfishing based upon
discrete biological benchmarks). These standards
required development of rebuilding plans to recover
overfished populations within strict time constraints.
For fish species that could not be recovered within
10 years following a moratorium on harvest, the law
required recovery in 1.5 generations in the life of the
fish under management. The scientific knowledge
about increased longevity and the law requiring
rebuilding schedules to be linked to generation time
made it possible for TACs of red snapper to be
increased over time, finally to 9.12 million lbs,
because of new longevity information that lengthened
the time permitted for rebuilding the stock until 2032.
However, all of the TAC increases that occurred
between 1990 and 1996, and continued high TACs
after 1996, also were predicated upon[50% reductions
in shrimp trawl bycatch of juveniles that, if
achieved, permitted a risk-prone (constant catch)
harvest strategy that preserved high catches for the
directed fisheries (Hood et al. 2007). This strategy
also required catch levels to remain constant for the
entire rebuilding period to recover the stock in 2032,
in the face of complaints by fishers who were (and are
again) seeing more fish as the stock recovers,
especially when strong year classes enter the fishery.
There were many attempts by science advisors to
assuage fisheries policy makers in the Gulf to adopt a
less risk-prone approach, without success, even as it
became apparent that a technological solution to
reducing numbers of red snapper from the shrimp
fishery bycatch was unlikely (Watson et al. 1997;
NOAA 2004). Clearly, the above history does not
capture all details. For more detailed information, see
Hood et al. (2007) and the Advisory Panel Reports
found at the following weblink (Reef Fish Stock
Assessment Panel Reports from 1990 forward at
http://www.gulfcouncil.org/, then Library, then
Downloadable Files).
A historical perspective
Based upon a historical reconstruction of the red
snapper fishery from its inception off Mobile, AL and
Pensacola, FL in the late 1880s until today, Shipp and
Bortone (2009) argue that ARs have substantially
increased red snapper stock size in the US Gulf. These
authors infer that red snapper stocks were smaller in
the eastern Gulf and effectively absent from the
western Gulf until ARs were deployed. In the eastern
Gulf, inference is drawn from the recent 20? years of
higher catches off Alabama, compared to lower
catches and short-lived fisheries for red snapper in
Rev Fish Biol Fisheries
123
the late 1870s to early 1900s. While we do not dispute
the historical record, there is an alternate interpretation
of the old landings data, and where on the shelf the
fishery was prosecuted. In that region of the eastern
Gulf, there is considerable low-relief, hard-bottom,
shell-rubble habitat that was formed during the last
sea-level transgression (Schroeder et al. 1988; Kennicutt
et al. 1995; Patterson et al. 2005; Dufrene 2005).
Much of this habitat has been repeatedly trawled and
broken up over time, but recent work in areas less
impacted by trawling indicates that these inshore
habitats still support juvenile red snapper and likely
once supported adults as well (Wells et al. 2008a, b). In
work off Alabama and Mississippi, Wells and colleagues
compared these habitats inside and outside of
the Alabama Artificial Reef Permit Zone, including
some stations in the Hugh Swingle Permit Area, which
has been a de facto no-trawl zone since 1986. Habitat
that had not experienced recent trawling was more
complex and supported a more diverse community of
benthic invertebrates and demersal fishes, including
juvenile and adult red snapper up to ages 5?. In
addition, the diet consumed by red snapper on these
habitats was more diverse than on similar habitats
outside of the no-trawl zone. We suggest that prior to
extensive trawling, these habitats likely had diverse
fish communities, and thus may have been the source
of red snapper in the early days of the fishery off
Mobile. Of course, it is impossible to know how dense,
or how abundant, red snapper were on these inshore
habitats, but they are less dense on low relief habitats
today than on nearby ARs, even in the no-trawl zone. Is
it possible that the red snapper fishery was founded on
these inshore habitats, that then were relatively quickly
depleted of fish, forcing fishers to prospect for new
fishing grounds without ever discovering the higherrelief,
shelf-edge features such as the Alabama Alps
and Pinnacles (Schroeder et al. 1988; Kennicutt et al.
1995) where red snapper likely were more abundant
(Gledhill 2001)?
The findings of Moe (1963) support this alternate
interpretation. A survey of offshore fishing in FL
completed in the early 1960s provides information
about habitat types and fisheries on the Northwest
Florida Coast (from east of Panama City, FL to the
AL state line). The report states that the bottom is
composed of sand and limestone, with rock outcroppings
that are more numerous in the eastern section of
the area than in the west. The report further indicates
that rock outcroppings generally occur in waters
greater than 12 fathoms, and are found in the bottom
of gullies and holes formed in the irregular sandy
bottom, or along the sides of ledges and cliffs that
drop to deeper water. The cliffs and ledges generally
lie parallel to the depth contours. The relief of these
features varies from a few feet to 11 or 12 fathoms.
Further, Moe reported that ‘‘the most sought after and
numerous fish in the catch of the sport and commercial
vessels is the Red Snapper. The fishing vessels
seek out rocky areas, wrecks of ships and airplanes,
and other irregularities of the bottom as these areas
are most productive’’ (page 50, paragraph 1 and 2).
This scenario also appears be plausible in the
western Gulf where prospecting in the early days failed
to find productive fishing grounds off the LA and
northeastern TX coasts (Shipp and Bortone 2009). But
again, it seems likely that the fishers in the early days
may have failed to locate the numerous shelf-edge
features well offshore of LA and TX, which in recent
history have been considered to be one of the centers of
abundance of the red snapper stock in the northern
Gulf (Goodyear 1995). In fact, Gledhill (2001) found
that these shelf-edge banks contained a higher proportion
of snappers (red and vermilion Rhomboplites
aurorubens) to total biomass than on similar features
in the eastern Gulf. This does not discount the
correlation between increased catches of red snapper
in the western Gulf and the increasing number of oil
and gas platforms, which serve as de facto ARs (Shipp
and Bortone 2009). However, we see this as a chicken
and egg argument. Is it likely that few red snapper
existed in the northwestern Gulf before ARs were
constructed, or did these man-made structures provide
a movement corridor for fish to move inshore where
they are more accessible to fishers? This mechanism of
cross-shelf movement by reef-associated fishes has
been postulated both for natural and artificial habitats
in the eastern Gulf (USGS 2008).
Another salient point that was overlooked in the
historical reconstruction of the red snapper fishery
(Shipp and Bortone 2009) was the enormous change
in hydrographic parameters in the northcentral and
northwestern Gulf brought about by flood protection
measures on the Mississippi River that began following
the 1927 flood (Barry 1997). These measures
took decades to complete (until the early 1970s when
Atchafalaya River discharge was fixed at 30% of total
Mississippi River discharge), but the end result was
Rev Fish Biol Fisheries
123
channelization of the river using levees and the
upstream construction of dams for power generation,
both of which acted to greatly reduce the amount of
freshwater and sediments reaching the shallow shelf
in the northern Gulf, while at the same time
stimulating productivity in the water column (Bianchi
et al. 2008). Within the last few years, the first author
was involved in a program to collect side-scan sonar
images of the Louisiana Artificial Reef Planning
Areas (PAs) in which were discovered large areas of
relatively high-relief, high-reflectance (solid) habitat,
especially in those PAs farthest from the Mississippi
and Atchafalaya River mouths. While different in
origin (lithified delta muds, tops of salt domes) than
low-relief features in the shallow eastern Gulf (old
beach ridges), their emergence as habitat as sediment
loads decreased may well have been coincident in
time with the increase in the number of ARs off LA,
and the higher catches of red snapper in the region. It
is also possible that this habitat may be contributing
to apparent recent increases in red snapper recruitment,
if indeed habitat is limiting for juveniles, and
the stock is finally beginning to recover.
As a final point in the discussion of history,
longliners were not prohibited from fishing in depths
of less than 50 fathoms in the northern Gulf until
1990, or about the same time the red snapper stock
was most depressed. Coincidently, this also is the
time when the number of oil and gas platforms was
most numerous in the Gulf. Because larger, older red
snapper have a tendency to move off structured
habitats as they grow older, these fish were susceptible
to longlining prior to 1990, likely decreasing
numbers of older, larger females in the population.
While these older fish today are less vulnerable to
fishing because of the longline ban and their numbers
are slowly increasing (SEDAR 2009), escapement to
older ages may still be too low to fill the ‘‘hole’’ in the
age structure. Remember, the fish that would be our
most productive spawners today (*20 years old)
were born during a period when stock biomass was
very low and longlining was occurring.
Final thoughts
From the beginning of red snapper management in
the Gulf (see review of the early days by Goodyear
1995), assessment results indicated that significant
reductions in bycatch mortality of juvenile red
snapper attributable to the shrimp industry, coupled
with decreased harvest of adults by the directed
fishery, perhaps, could result in rapid recovery of the
stock (see Reef Fish Stock Assessment Panel Reports
from 1990 forward at http://www.gulfcouncil.org/,
then Library, then Downloadable Files). Despite the
enormous body of knowledge that has been amassed
about red snapper since that time, the message has
remained consistent. Given that offshore shrimp
fishing effort now (early 2010) is down by as much as
75–85% (SEDAR 2009) owing to recent coastal
storm damage, economic woes, high fuel prices and
cheap imported shrimp, bycatch has been declining
for the last several years, especially since 2002, and
the directed fishery (which also has been negatively
impacted by high fuel prices) has recently been
constrained by the 2006 MSRA to lower total
allowable catches (TACs). Simply put, the recovery
formula long prescribed in the agency assessments
has finally been realized, although recent estimates of
M for age-0 and age-1 red snapper may diminish the
role that bycatch reduction can play in recovery of the
stock. Even so, recent sampling off LA and the FL
panhandle (Dance 2008; SEDAR 2009) indicates that
the increase in numbers still is mostly comprised of
3–7 year old fish, but numbers are indeed increasing.
Given that artificial reefs and especially oil and gas
platforms have been in place for many years (Shipp
and Bortone 2009), it seems counterintuitive to award
credit to artificial structures for the beginning stages
of stock recovery that are just now becoming apparent.
This incongruity is particularly exaggerated
when considering that stock rebuilding was basically
non-existent for 20 years, and not until long prescribed
management measures were finally put in
place. This may be especially true in the eastern Gulf
off AL where the large AR permit zones have created
a de facto refuge from shrimp trawling, thus bycatch
of juvenile red snapper, making it difficult to differentiate
the reef effect from the reduction in bycatch
and decreases in destruction and degradation of natural
hard bottom habitat.
The above analyses and summary comments are
not meant to be an indictment of ARs and AR
programs. Legitimate benefits of ARs can and have
been achieved (Bortone 1998; Pitcher and Seaman
Rev Fish Biol Fisheries
123
2000; Claudet and Pelletier 2004; Page et al. 2007),
especially when ARs serve as no-take reserves
(Schroeder and Love 2002). However, most agree
that goals and objectives of an AR or an AR program
need to be explicitly stated in order to assess
‘‘performance’’. When this is done, analyses of
measurable parameters relative to stated objectives
show benefits ranging from increased consumptive
and non-consumptive use, to improved marine protected
area performance (Ramos et al. 2007; Claudet
and Pelletier 2004).
Recent studies are instructive in reminding all
parties that there are highly complex questions of
community-scale ecology underlying the single-species
‘‘patterns’’ that we often use to justify large-scale
deployments of ARs. For example, substantially
modified trophic interactions (i.e., transformations,
see Shipp 1999), can develop requiring extensive
study and experimentation to resolve; these transformations
cause both direct and indirect effects in
ecosystems in which they occur, but may not apply to
other locations (Powers et al. 2003; Grabowski and
Powers 2004; Shipley 2008). We encourage careful
study and experimentation, as was done in the papers
cited above, and Page et al. (2007), to address
spatially-explicit, objective driven, and quantifiable
performance of ARs in the Gulf (Strelcheck et al.
2005; Lindberg et al. 2006) and elsewhere. We also
believe that improved fishing opportunities and
higher catches should not be the only metric used
to assess AR performance.
Finally, regardless of the cause(s) of the putative
increase in red snapper stock-specific productivity,
higher productivity conveys higher potential biomass
levels (i.e., carrying capacity), thus resulting in
higher, not lower (Shipp and Bortone 2009) rebuilding
targets (i.e., over fishing levels (OFL), biomass at
OFL (BOFL); see SEDAR 2009 for details). Therefore,
further reductions in annual catch limits (to end
overfishing by 2010 and reach OFLs in the long-term)
may actually be needed for a more prolonged period
of time because we may have higher goals to reach.
The assessment models are forward looking because
science has recognized that things can and do change
in ecosystems. So all of the assessments compare
current biological benchmarks to future stock status
given a stable age distribution (i.e., a fully complete
age structure). Most importantly, if spawning stock
biomass is still too low to produce the minimum
number of eggs (primarily due to the truncated age
distribution, Walters et al. 2008a) to avoid recruitment
overfishing, even accepting the likelihood for
some recruitment compensation, the debate (including
AvP) about artificial reefs is rendered ineffectual.
The bottom line is that if carrying capacity for adults
has increased, yet escapement to older ages is still too
low, we would now have a much larger and longer
row to hoe to recover the red snapper stock to BOFL.
In their recent perspective, Shipp and Bortone
(2009) argue that the red snapper stock is not only
larger, but also is more productive today due to ARs;
therefore, red snapper could not possibly be overfished.
However, apical F estimates for various
fisheries have been quite high (0.4–1.0 year-1; Porch
2007), and there are other empirically derived
symptoms that the red snapper stock is overfished
(Jackson et al. 2007; Nieland et al. 2007). Although
estimates are that future yields (i.e., longterm
productivity) could be*29 higher than any recorded
landings (note: landings data are sparse before about
1980), the stock cannot recover to threshold biomass
levels at current F rates. Shipp and Bortone (2009)
argue further that managers should not have to reach
a BOFL threshold based upon current (higher) estimates
of stock productivity. In effect, they argue that
carrying capacity and productivity have increased
substantially, while contending that BOFL should not
scale to these increases. We think this point should be
noted by our readers, regardless of the ultimate
cause(s) of the presumed higher productivity in the
stock. (Note: Porch (2007) lists several as yet
untested hypotheses about causes of apparent
increases in productivity, with ARs among them).
In the meantime, the preponderance of scientific
information that is used in the agency assessment
process, and the simple arguments made here, do not
support the position that artificial reefs have
increased red snapper stock size sufficiently to defer
compliance with the MSRA.
Acknowledgments We thank two anonymous reviewers for
their comments on an earlier draft of this manuscript. None of
the authors were compensated for participating in this effort.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which
permits any noncommercial use, distribution, and reproduction
in any medium, provided the original author(s) and source are
credited.
Rev Fish Biol Fisheries
123
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Replies

  • ANUMBER1ANUMBER1 Posts: 8,466 Admiral
    ok... I'll play...
    I am glad to only be a bird hunter with bird dogs...being a shooter or dog handler or whatever other niche exists to separate appears to generate far too much about which to worry.
  • Mackeral SnatcherMackeral Snatcher Posts: 10,435 AG
    I tried but fell asleep.
    THERE SHOULD BE NO COMMERCIAL FISHING ALLOWED FOR ANY SPECIES THAT IS CONSIDERED OVERFISHED.
  • FS JeffFS Jeff Posts: 371 Moderator
    Basically, what you are reading is an allergic reaction to the notion that human activity, in this case reef-building, might actually enhance fisheries.

    Perhaps, if we pulled up all the reefs in the Gulf, demolished all the drilling rigs, and consciously drove the human birth rate and thus fishing pressure to zero, in 52 years a scientist funded by the Pew foundation would, at long last, identify a 53-year-old red snapper and declare the snapper population recovered.
    Jeff Weakley
  • Jack HexterJack Hexter New Port RicheyPosts: 4,151 Moderator
    Jeff

    I wasn't about to try and read/understand the op's post, but isn't your summary the same as what Bob Shipp said a long time ago.
  • FS JeffFS Jeff Posts: 371 Moderator
    Well I can't speak for Dr Shipp, but he has published some convincing arguments linking red snapper to reef development.

    I don't get on the Forum much these days but I did see the post and it's certainly obscure stuff for lay reader. But just because something reads authoritatively doesn't mean it's the last word. I'm not assailing the research presented, nor the character of the authors, but I think readers should be aware there are diverse views on red snapper.

    Anyways good to see differing views on the Forum, but maybe Cliffs Notes version might be helpful next time.
    Jeff Weakley
  • BubbaIIBubbaII Posts: 328 Deckhand
    FS Jeff wrote: »
    Well I can't speak for Dr Shipp, but he has published some convincing arguments linking red snapper to reef development.

    I don't get on the Forum much these days but I did see the post and it's certainly obscure stuff for lay reader. But just because something reads authoritatively doesn't mean it's the last word. I'm not assailing the research presented, nor the character of the authors, but I think readers should be aware there are diverse views on red snapper.

    Anyways good to see differing views on the Forum, but maybe Cliffs Notes version might be helpful next time.

    Don't know all of those authors, but those I do know some and they are pretty heavy hitters: Cowen, Powers, Grimes, Patterson, Diamond, Hilborn. All highly respected fishery biologists, many whom have served on, or do serve on, the Council's SSC.

    And they pretty well back up their assertions with citations of other scientific publications. The Shipp and Bortone articles they note were not scientific publications; just editorials. Gives one pause to consider......
  • Tom HiltonTom Hilton Posts: 1,572 Captain
    Cowen claims the snapper off of Alabama are being populated by fish swimming from the banks offshore of Texas - hogwash. Best "science" money can buy.

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