The common snook, Centropomus undecimalis, is a popular
game fish in Florida. Snook have presented challenges to management
because of complex life history and distribution.
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INTRODUCTION
The common snook, Centropomus undecimalis, is a popular
gamefish in Florida that has presented challenges to management
because of its complex life history and distribution. Because snook
may reach maturity between the ages of 4 an 6 and may live more
than 20 years, they may be easily overfished. In addition to the
mortality associated with exploitation, snook are vulnerable to
water temperatures less than 55-56 degrees Farenheit; episodic,
massive kills have occurred during severe winters. Snook
populations on the two coasts of Florida have significantly
different growth patterns and different reproductive schedules.
Common snook are protandric hermaphrodites, i.e., some
portion of male snook reverse sex and become females between the
ages of one and seven years (Taylor et al. 1993). Additionally,
Atlantic-coast snook are genetically different from gulf-coast
snook (Tringali and Bert 1996). Because snook support one of the
largest and most popular fisheries in Florida and because of their
complex biology and susceptibility to low water temperatures,
managers have promulgated strict regulations that emphasize low bag
limits, closed seasons, and the value of catch-and-release fishing
in an effort to ensure high levels of abundance.
Historical levels of abundance
Prior to World War II, human consumption of snook was low
because the fish developed a "soapy" taste as a result of cleaning
practices that left the skin attached to the fillet. Snook were
considered "cat food," and commercial fishermen were paid between
$0.025-0.04 per pound (Marshall, 1958). As demand increased during
the protein-short war years, techniques for using large,
shore-based haul-seines and gill-nets were developed that allowed
harvesters to catch from 5,000 to 20,000 lbs. of snook per set.
Annual landings of snook in Florida during 1941-1955 averaged
498,492 lbs. and ranged between 374,312 and 800,698 lbs. at prices
of $0.14-0.25per pound. Harvest peaked in 1948, followed by annual
declines until 1957; these declines were partially due to decreased
demand and partially to the prohibition of haul seines in Lee
County in 1947 and throughout the state in 1951. During the
mid-fifties, anglers reported declines in abundance at the same
time steady decreases in commercial landings were reported, and the
Florida legislature passed stricter regulations in 1957. These
rules made it illegal to buy or sell snook, set the bag limit at
four snook per day, and made legal capture of snook by "hook and
line" only.
Between 1957 and 1976, there was a hiatus in research and
technical information regarding snook abundance; although, fishing
guides and members of conservation organizations continued to
report that snook populations were declining (Bruger and Haddad,
1986). In 1976, biologists from the Florida Department of Natural
Resources, Marine Research Laboratory, (later known as, Department
of Environmental Protection, Florida Marine Research Institute,
DEP, FMRI)* began a mark-recapture study in the Naples-Marco Island
area to determine annual estimates of abundance of snook
populations in southwest Florida. Snook were collected in a 100-m
beach seine each summer from 1976 through 1987. The area was
sampled again in 1994, and another estimate of the population was
made.
Current levels of abundance
Results of the tagging program indicated that snook abundance in
the Naples area had declined by approximately 70% between 1977 and
1981 (Fig. 1a.), presumably because of the effects of increased
exploitation and a disastrous freeze in January 1977 (Gilmore
et al., 1978). As a result of these findings, the
legislature, in 1981, set possession limits at two snook per day
with the provision that no snook longer than 18 inches fork length
could be kept during June or July 1982-1986. In 1982, the snook
fishery was closed January, February, June, and July during
1982-1986. These rules were intended to halt the decline in
abundance by eliminating the take during the winter months, when
snook become lethargic in the cold water and so can easily be
harvested in dip nets, and by eliminating the take during the
summer spawning season, when catch rates were the highest. Despite
these added restrictions, snook abundance remained low in the
Naples area during 1983-1986.
In 1985, the newly created Florida Marine Fisheries Commission
(FMFC) permanently closed the snook fishery during the months of
January, February, June, July, and August; increased the minimum
legal size to 24 inches total length; and established a daily bag
limit of two snook, only one may exceed 34 inches total length. The
Naples index for 1987 indicated that the levels of snook abundance
were still depressed but that they approximated the levels of 1981,
reflecting an improvement. The tagging study was conducted again in
the summer of 1994, and that estimate was also greater than the
yearly estimates for the period 1981-1986. Although it is difficult
to make conclusions from these data because of the large error
associated with the prior estimates, the estimates of 1987 and 1994
indicate that the decline has abated and that the snook populations
in the Naples area may have stabilized or may have increased to the
levels of the early eighties.
In 1984, FMRI biologists began to monitor levels of snook
abundance annually along the southeast coast of Florida using
similar mark-recapture procedures to those used in Naples. The
capture gear was hook and line instead of seines. This research was
conducted through 1997 which provided continuous estimates of the
abundance of common snook in the Jupiter-Palm Beach area. Even
though 95% confidence limits overlap for most estimates, the mean
abundance indices increased during the late eighties (Fig.1b.).
Mean east-coast estimates were lower, though not significantly,
during 1991-1994, perhaps because of increased fishing effort
combined with the effects of the severe winter of 1989-1990.
Biologists from DEP, FMRI began monitoring levels of snook
abundance in two micro-habitats of Tampa Bay in the summer of 1990
using a trammel net as the capture gear and the Petersen one-time
mark-recapture technique to make annual population estimates.
Current levels of abundance in both the upper bay MacDill site and
the lower bay Port Manatee site are significantly higher than
levels determined at the beginning of the study (Figs. 2 a. and
b.). These increases may be the result of increased recruitment
after the depletion of Tampa Bay stocks during the extreme winter
of 1989-1990. We cannot estimate either the total snook mortality
sustained during this cold-kill event or the levels of abundance in
Tampa Bay prior to 1990; however, more than 60,000 adult snook were
estimated to have been killed in the Manatee and Little Manatee
rivers in December 1989.
The National Marine Fisheries Service, Marine Recreational
Fisheries Statistical Survey (MRFSS) landings summary has been
recorded since 1982 and provides other fishery data used to assess
the status of snook stocks in Florida. The number of intercepts has
increased annually on both coasts from about 55 in 1982 to more
than 900 in 1995 (Figs. 3a. and b.). Effort increased from fewer
than 100,000 trips on each coast in 1982 to more than 700,000 trips
on the Atlantic coast and more than 800,000 on the gulf coast in
1995. Effort and catch-per-unit-effort (CPUE) have increased
significantly. The number of snook harvested increased from about
5,000 fish on the Atlantic coast and about 20,000 on the gulf coast
in 1982 to about 44,000 snook on each coast in 1995. The
simultaneous increase in effort and CPUE indicates that current
levels of abundance have surpassed the levels of the early
eighties. The actual harvest represents only six and eight percent
of the total snook caught on the Atlantic and gulf coast,
respectively, demonstrating that the snook fishery in Florida has
primarily become a catch-and-release fishery.
Spawning potential ratios
The strategy for managing snook in Florida has been to maintain
very high standing stocks by instituting low bag limits, closed
seasons, and slot limits and by encouraging catch-and-release
fishing. In 1993, the FMFC adopted the concept of spawning
potential ratios (SPR) as the primary method with which to assess
snook populations in Florida. In 1991, using catch-curve
information from known ages of female snook collected during a
previous life-history study, FMRI biologists determined that SPR
values for Atlantic and gulf coast snook populations were 48% and
38%, respectively. In 1993, the FMFC established a management goal
of maintaining a minimum SPR of 40% for snook populations on both
coasts of Florida. This level is higher than the levels adopted for
other inshore species in Florida e.g., red drum, spotted seatrout,
and mullet, but it is warranted because snook are vulnerable to
cold kills coupled with the uncertainties associated with managing
a protandric hermaphrodite.
All available information indicates that the current snook
management strategy is viable and has achieved the intended
results. It appears that stringent management measures, combined
with recent mild winters, have allowed snook abundance to rise to
high levels (Nelson, 1993). The estimated SPR values for Atlantic
stocks in 1996 and 1997 were 44 and 40%, respectively, while these
values for the gulf stocks were 41 and 40%, respectively (Muller
and Murphy, 1998). The weakness inherent in using the SPR analyses
to assess fish stocks is the assumption that natural mortality
remains constant. Random catastrophic cold kills and red tide
events render that assumption invalid. This weakness and the
reluctance to independently sample adults of a popular gamefish may
provide the impetus to manage snook by using other techniques, such
as CPUE, abundance indices, survival rates derived from
tag-recovery studies, or angler satisfaction ratings.
Future considerations
Future snook management must be tempered with the realization
that during the past 50 years in Florida, more than half of the
snook's principal habitat, mangrove shoreline, has been lost
(Bruger and Haddad, 1986). Marshall (1958) stated that closing the
commercial fishery for snook and imposing size restrictions had
done little to halt the population declines that began in the
fifties and that these declines were more likely due to alterations
of the habitat than to fishing. Because of habitat reduction,
increased exploitation, and sporadic cold kills, it is prudent to
maintain strict regulations on the fishery to ensure high levels of
stock abundance. However, high levels of snook abundance may not be
sustainable unless the habitat critical to this species is managed
as well.
Common snook is an economically valuable resource to the state
of Florida; enthusiasts generate large revenues in pursuit of this
"species of special concern." Anecdotal reports and scientific data
indicate that snook abundance has increased over the last ten years
as a result of mild winters, restrictive management, and angler
conservation. Even though it may not be possible to restore the
populations to levels of the pre-World War II era because of the
changes in habitat and increased fishing effort, it may be possible
in the short term, to maintain or even increase, levels of
abundance if harvest remains low.
* The FMRI's name changed again in July 2004 to Florida Fish
and Wildlife Conservation Commission (FWC), Fish and Wildlife
Research Institute (FWRI).
References
Bruger, G. E., and K. D. Haddad. 1986. Management of tarpon,
bonefish and snook in Florida. In R. H. Stroud (ed.)
Multi-jurisdictional management of marine fishes: Marine
Recreational Fisheries II. Proceedings of the eleventh annual
marine recreational fisheries symposium. Tampa, FL. May, 1986.
National Coalition for Marine Conservation, Inc. Savannah,
GA.
Gilmore, R. G., L. H. Bullock, and F. H. Berry. 1978. Hypothermal
mortality in marine fishes of south-central Florida: January, 1977.
NE Gulf. Sci. 2(2):77-97
Marshall, A. N. 1958. A survey of the snook fishery of Florida,
with studies of the biology of the principal species,
Centropomus undecimalis (Bloch). Fla. Board Conserv. Mar.
Res. Lab. Tech. Ser. No. 22.
Muller, R. G., and M. D. Murphy. 1998. A stock assessment of
common snook, Centropomus undecimalis. Dept. Env. Prot.
Fl. Mar. Res. Inst. 100 Eighth Ave. SE, St, Petersburg, FL.
33701.
Nelson, R. 1993. A review of snook management: current status and
potential issues. Florida Marine Fisheries Commission Staff Report.
May 27, 1993. Tallahassee, FL.
Taylor, R. G., J. A. Whittington, and H. J. Grier. 1993. Biology
of common snook from the east and west coasts of Florida. Study 3,
Sect. 1. In Investigations into nearshore and estuarine
gamefish distributions and abundance, ecology, life history, and
population genetics in Florida.R. E. Crabtree, T. M. Bert, and R.
G. Taylor, eds. FDNR/FMRI Rep. No. F0165-F0296-88-93-C. U. S.
Department of the Interior, Fish and Wildlife Services, Washington,
D. C. Pp 1-51.
Tringali, M. D., and T. M. Bert. 1996. The genetic stock structure
of common snook Centropomus undecimalis. Can. Jour. Fish
Aquat. Sci. 53 (5): 974-984.
A Historical Review of Snook Regulations in
Florida:
1947
- Snook haul seines made illegal in Lee County
1951
- Snook haul seines made illegal in Collier County
1953
- Minimum size set at 18 inches fork length
1957
- Snook made illegal to buy or sell
- Capture by hook and line only
- Bag limit set at four snook per day, eight snook possession
limit
1981
- Bag limit reduced to two snook per day, two snook possession
limit
- No snook less than 26 inches fork length may be taken in June
or July during 1982-1986
1982
- June and July of 1982 closed to snook possession.
1983
- January and February 1983-1986 closed to snook possession
- June and July 1983-1986 closed to snook possession
1985
- January, February, June, and July closed permanently to snook
possession
- August 1985-1986 closed to snook possession
- Minimum size increased to 24 inches total length
- Only one snook may be greater than 34 inches total length
1987
- All species of the Genus Centropomus covered by the
regulations
- August closed permanently to snook possession
- All snook to be landed whole
- Use of treble hooks prohibited with natural baits
1994
- Closed winter season changed to 15 December through January
31
1999
- Slot limit set at 26 inches minimum-34 inches maximum total
length
To view the most current regulations on snook, please visit the
Florida Administrative Code Web
site-Chapter 68B-21.
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