Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

<em>Abstract.</em>—Red snapper <em>Lutjanus campechanus </em>were sampled from commercial landings from the Gulf of Mexico (GOM) off Louisiana from October 2001 to May 2004. Fork length (FL), eviscerated weight, otoliths (both sagittae), and sex determinations were taken from 2,900 specimens; FL was subsequently converted to total length (TL) with the equation TL = 1.073 (FL) + 3.56. Red snapper ages (<EM>N </EM>= 2,867) estimated from counts of opaque annuli in otoliths ranged from 1 to 14 years; however, the vast majority (97.7%) of these were ages 2 to 6 years and the modal age was 3 years. Total lengths among 2,897 specimens ranged from 278 to 940 mm, modal TL was 400 mm, and 98% of all specimens were less than 600 mm TL. We also investigated the fate of red snapper regulatory discards (individuals <381 mm [15 in] TL) during 16 trips on working commercial vessels; over two-thirds of 4,839 red snapper assigned among four discard fate categories (ranging from alive and vigorous to dead) were returned to the water either in moribund or dead condition. Among 399 potential discards retained for age and length analyses, 86% were between 12 and 15 in (305–381 mm) TL and 85% were 2 years of age. The minimum size regulation appears to do little to protect juvenile red snapper from commercial fishing mortality. Heavy red snapper mortality, which begins as bycatch mortality in shrimp trawls, continues as discard mortality at sub-legal lengths when they first recruit to the offshore fishing grounds, and persists as harvest mortality among the youngest legal year- and size-classes. If the minimum size limit is intended to provide a respite from such mortality, a reconsideration of the utility of the minimum length regulation in the commercial harvest of red snapper may be warranted.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

<em>Abstract.</em>—Trawl surveys were conducted to measure patterns of habitat use by newly settled red snapper <em>Lutjanus campechanus </em>at three natural banks on the inner continental shelf of Texas. Digital side-scan sonar and multibeam bathymetric data were used to define inshore (mud), ridge (shell), and offshore (mud) habitats for Freeport Rocks, Heald Bank, and Sabine Bank. Otter trawls were conducted July through September in 2003 (Heald Bank, Sabine Bank) and in 2004 (Freeport Rocks) during the settlement period of red snapper. Freeport Rocks had markedly higher densities of red snapper (91 ha^⁻1) in 2004 than Heald Bank (6 ha^⁻1) or Sabine Bank (<1 ha^⁻1) in 2003. A significant habitat effect was observed at Heald Bank and densities were higher at offshore mud habitats; no habitat effect was detected for Freeport Rocks or Sabine Bank. Growth rates varied from 0.86 mm‧d^⁻1 at Sabine Bank up to 1.12 mm‧d^⁻1 at Freeport Rocks, and rates were higher on inshore and offshore mud than ridge habitats. Otolith-based estimates of age indicated that settlers were first detected at 22–28 d and the majority of individuals were 30–60 d. Hatch dates peaked from early June to early July in both 2003 and 2004. Results from this study indicate that both shell and inshore and offshore mud habitats associated with these natural banks serve as settlement habitat of red snapper, and all three habitats have the potential to function as nursery areas of this species.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

<em>Abstract.</em>—Eleven taxa of snappers were found among the 20,301 snapper larvae examined from over 14,000 bongo and neuston samples collected during SEAMAP surveys, 1982 to 2003. During that time series, a total of 639 red snapper <em>Lutjanus campechanus </em>larvae were identified in bongo samples and 1053 larvae in neuston samples. Red snapper larvae first appeared in May and were present as late as November. Months of highest occurrence and abundance were July and September when larvae were taken in 12.7% and 11.0% of bongo samples, and in 7.6% and 8.4% of neuston samples. Mean abundance in those months was 1.18 and 0.82 larvae under 10 m² of sea surface for bongo samples and 0.36 larvae per 10 min for neuston samples. By November, percent occurrence was less than or equal to 0.2% and mean abundance was less than 0.01 larvae in samples from either gear. Larvae identifiable as red snapper ranged in body length from 2.4 to 19.2 mm (mean = 5.12, median = 4.60) in bongo net samples; and 2.7–24.0 mm (mean = 4.37, median = 4.00) in neuston net samples. Over 95% of larvae in bongo samples were less than or equal to 8.3 mm and in neuston samples were less than or equal to 5.6 mm. Larvae were captured throughout the survey area but were consistently observed in greatest abundance at stations on the mid-continental shelf west of the Mississippi River, especially off western Louisiana and central Texas. This time series of observations is the data set from which annual estimates of larval red snapper abundance were derived for use as a fishery independent index of adult stock size.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

<em>Abstract.</em>—Video estimation of the relative abundance of fishes is a noninvasive method commonly used to assess fish densities. This technique can be used to characterize habitat use patterns either of fish assemblages or of a particular species of interest. The objectives of this study were to quantify relative abundance of red snapper, <em>Lutjanus campechanus</em>, and to characterize with video methodology the associated fish assemblages over different habitat types. Fishes were enumerated over sand, shell, and natural hard bottom reef habitats in the north-central Gulf of Mexico (GOM) off Alabama on quarterly cruises over a two-year period with a baited stationary underwater video camera array. Red snapper showed both significantly higher abundance and larger size over the reef habitat; however, no seasonal effects were observed, indicating temporal abundance patterns were consistent among seasons. Fish assemblages differed among habitats, with significant differences between reef and shell assemblages. Efforts to identify the species that most contributed to these differences indicated that the red snapper accounted for 59% of the overall similarity within the reef fish assemblage and 20% of the total dissimilarity between the shell and reef fish assemblages. This study highlights the utility of applying video techniques to identify the importance of sand, shell, and reef habitat types both to different life stages of red snapper, and to the different fish assemblages occupying distinct habitats in the north-central GOM.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

<em>Abstract.</em>—Red snapper, <em>Lutjanus campechanus</em>, has been fished for over a century, with management beginning in the Gulf of Mexico (Gulf) in the early 1990s when perceptions of a declining population size surfaced. Red snapper are managed as a unit stock and the fishery management plan is based upon minimal data regarding reproductive output, and size and age at sexual maturation is not certain. Differences in size and age at sexual maturity of red snapper between the northeast and north-central Gulf were evaluated to test whether the population conforms to the unit stock hypothesis. Red snapper were collected during the spawning season in 1999, 2000, and 2001 from the Gulf off Alabama and Louisiana and were used to describe maturation schedules. Progression of oocyte maturation to vitellogenesis was used to define and identify sexually mature females. Combined data showed the smallest mature red snapper was 267 mm fork length (FL) and was two years old. The smallest with hydrated oocytes, indicative of imminent spawning, or postovulatory follicles, indicative of recent spawning, were 285 mm and 297 mm FL respectively, and both were two years old. Red snapper off Alabama reached maturation at smaller sizes and younger ages than those sampled off Louisiana. Growth rates did not differ between the regions. Such differences in maturation schedules may document an important stock response to reductions in population size.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

<em>Abstract.</em>—Statistics on the commercial landings of red snapper <em>Lutjanus campechanus </em>in the United States have been recorded by the National Marine Fisheries Service (NMFS) and its predecessors as far back as 1880. However, there are many gaps in the historical record. Censuses were conducted sporadically prior to 1949 and the water body where the catch was taken was not consistently recorded until 1963. Past assessments of the status of red snapper in the U.S. Gulf of Mexico have avoided these problems by using only data collected after the early 1960s. Unfortunately, there are indications the stock may have already been depressed by that time and the resulting lack of contrast in the data has made it difficult to estimate important benchmarks such as the maximum sustainable yield. For this reason, the participants of several SEDAR (Southeast Data and Assessment Review) workshops strongly recommended reconstructing the catches as far back as possible using whatever auxiliary information might be available. This paper uses statistics from several state and private agencies to supplement NMFS landings statistics and then uses historical accounts dating back to the 1840s to help fill the remaining gaps. The data suggest that a substantial red snapper fishery existed as early as 1872 and that by the turn of the century the landings were comparable to those of recent times, albeit heavily dependent on snapper grounds located in Mexico. The trends of the reconstructed landings are qualitatively consistent with major events in the history of the fishery, but considerable uncertainty remains over the many uncanvassed years between 1890 and the 1920s.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

<em>Abstract.</em>—Red snapper, <em>Lutjanus campechanus</em>, is a heavily exploited reef fish that is harvested in the Gulf of Mexico from both natural and artificial reefs. Since regulations were imposed in 1990, the stock has begun to recover; this recovery has also been attributed in part to an increase in artificial habitats/reefs. However, little is known about the role artificial reefs play in the trophic dynamics of the species. To this end, the seasonal and size-specific diet of red snapper was examined through stomach content analysis of individuals collected from artificial reefs in the north-central Gulf of Mexico off Alabama between May 1999 and April 2000. Diet information was subsequently combined with data from the literature to obtain a first-order estimate of prey demand of the red snapper population on artificial reefs off Alabama. Results indicate both that diet varied with season and red snapper size and that the overall diet was comprised primarily of demersal crustaceans, fish, and pelagic zooplankton. Annual prey demand of the red snapper population on Alabama artificial reefs was estimated to be over 31 million kg. Red snapper derived most of their nutrition from sand/mud- and water column-associated organisms, not from organisms associated with reefs. Based on these results, and the results from other red snapper studies off Alabama, Alabama artificial reefs may be attracting, not producing red snapper.