Search

The authors wish to thank Chelsie Smith, Chelsie Money and staff from the Thad Cochran Marine Aquaculture Cen-ter for assistance with spawning and larval culture trials and husbandry of stocks, and C.S. Lee and Jason Hide forgreatly appreciated contributions to early spawning trials. The Mississippi Department of Marine Resources(Tidelands Trust Funds Program award #S-09-USM/GCRL-M201-13-01), NOAA and the Gulf States Marine Fisher-ies Commission (award #NA15NMF4720399, sub-award #ACQ-210-039-2020-USM2) and Perciformes Group LLCare acknowledged for funding support.

The overexploitation of many traditionally targeted reef fishes, such as red snapper, Lutjanus campechanus (Poey, 1860), alongside the implementation of increasingly restrictive management measures on those species, has led to increased targeting of conventionally discarded Gulf of Mexico gray triggerfish, Balistes capriscus Gmelin, 1789, commercially and recreationally. The goal of this study was to assess age and growth of gray triggerfish from the Alabama Artificial Reef Zone in the north-central Gulf of Mexico. Gray triggerfish (n = 1135) were collected predominantly from artificial habitat during 1999–2017. Specimens were sexed macroscopically and ages were assigned by counting translucent increments in sections of the first dorsal spine. Fish ranged in size from 22 to 617 mm fork length. The oldest female was assigned an age of 9 yrs; the oldest male, 10 yrs. A suite of growth models was tested to develop combined and sex-specific models. The von Bertalanffy growth function best fit the combined data with parameters L∞ = 488.63 (SE 5.19), k = 0.57 (SE 0.02), and t 0= –0.27 (SE 0.03). Mean size-at-age differed between sexes for six of the eight ages which possessed sample sizes large enough to make comparisons. Growth differed between sexes, and the best-fitting version of the von Bertalanffy growth function permitted L∞ to vary by sex [female L∞ = 480.26 (SE 7.99); male L∞ = 532.89 (SE 8.95); k = 0.44 (SE 0.04); t 0 = –0.78 (SE 0.16)]. These findings enhance our knowledge of the age and growth of Gulf of Mexico gray

Age and growth of early-life-stage Atlantic tarpon Megalops atlanticus collected from Mississippi coastal waters in the northcentral Gulf of Mexico (GOM) are described using otolith microstructure analysis. Tarpon leptocephali (n = 95, 16.0-27.8 mm standard length, LS ) collected from June throughOctober 2013-2018, ranged in age from 22 to 43 days (mean = 30.9 ± 0.5 days). Leptocephalus somatic growth rates ranged 0.46-1.24 mm day-1 (mean = 0.76 ± 0.02 mm day-1 ), and leptocephalus otolith growth rates ranged 1.78-3.97 μm day-1 (mean = 2.58 ± 0.04 μm day-1 ). Growth rates were inversely correlated to leptocephalus age, indicating the shrinkage phase associated with leptocephalus metamorphosis. Juvenile tarpon (n = 358, 50-359 mm fork length, LF ) were collected from August through December 2007-2018. Juveniles exhibited a positive allometric relationship (adjusted R2 = 0.99, P

In the northern Gulf of Mexico (GOM), whale sharks (Rhincodon typus) form large aggregations at continental shelf-edge banks during summer; however, knowledge of movements once they leave aggregation sites is limited. Here we report on the seasonal occurrence of whale sharks in the northern GOM based on over 800 whale shark sightings from 1989 to 2016, as well as the movements of 42 whale sharks tagged with satellite-linked and popup satellite archival transmitting tags from 2008 to 2015. Sightings data were most numerous during summer and fall often with aggregations of individuals reported along the continental shelf break. Most sharks (66%) were tagged during this time at Ewing Bank, a known aggregation site off the coast of Louisiana. Whale shark track duration ranged from three to 366 days and all tagged individuals, which ranged from 4.5 to 12.0 m in total length, remained within the GOM. Sightings data revealed that whale sharks occurred primarily in continental shelf and shelf-edge waters (81%) whereas tag data revealed the sharks primarily inhabited continental slope and open ocean waters (91%) of the GOM. Much of their time spent in open ocean waters was associated with the edge of the Loop Current and associated mesoscale eddies. During cooler months, there was a net movement southward, corresponding with the time of reduced sighting reports. Several sharks migrated to the southwest GOM during fall and winter, suggesting this region could be important overwintering habitat and possibly represents another seasonal aggregation site. The three long-term tracked whale sharks exhibited interannual site fidelity, returning one year later to the vicinity where they were originally tagged. The increased habitat use of north central GOM waters by whale sharks as summer foraging grounds and potential interannual site fidelity to Ewing Bank demonstrate the importance of this region for this species.

The timing and extent of international crossings by billfishes, tunas, and sharks in the Cuba-Mexico-United States (U.S.) triangle was investigated using electronic tagging data from eight species that resulted in >22,000 tracking days. Transnational movements of these highly mobile marine predators were pronounced with varying levels of bi- or tri-national population connectivity displayed by each species. Billfishes and tunas moved throughout the Gulf of Mexico and all species investigated (blue marlin, white marlin, Atlantic bluefin tuna, yellowfin tuna) frequently crossed international boundaries and entered the territorial waters of Cuba and/or Mexico. Certain sharks (tiger shark, scalloped hammerhead) displayed prolonged periods of residency in U.S. waters with more limited displacements, while whale sharks and to a lesser degree shortfin mako moved through multiple jurisdictions. The spatial extent of associated movements was generally associated with their differential use of coastal and open ocean pelagic ecosystems. Species with the majority of daily positions in oceanic waters off the continental shelf showed the greatest tendency for transnational movements and typically traveled farther from initial tagging locations. Several species converged on a common seasonal movement pattern between territorial waters of the U.S. (summer) and Mexico (winter).

Inter-annual and ontogenetic differences in diet and feeding intensity were examined for larval Atlantic bluefin tuna, Thunnus thynnus (Linnaeus, 1758), collected from the central Gulf of Mexico (GOM) during May 2008, 2009, and 2010 [n = 100; 3.0–6.7 mm body length (BL)]. Predominant prey groups were copepods, cirripeds, and cladocerans. Inter-annual differences in diet resulted from changes in the consumption of copepods and unique prey groups (e.g., cladocerans). Body length had an effect on T. thynnus diet, and a relative increase in copepod consumption occurred beyond 5 mm. Feeding intensity (i.e., the number of prey per digestive tract) was higher during 2010 than 2008 and 2009 and positively correlated with increasing T. thynnus BL. No fish prey were observed, which suggests piscivory in GOM T. thynnus does not occur at sizes

Spotted Seatrout Cynoscion nebulosus are a highly valued recreational inshore species in Mississippi coastal waters. The accurate description of the length-at-age relationship is critical for assessment efforts of the stock. Because Spotted Seatrout exhibit small-scale movements, the stocks in the Gulf of Mexico are managed as state-specific units. Therefore, local demographic estimates of length at age are needed for assessment. We estimated the length-at-age relationship of Spotted Seatrout in Mississippi by using tag recapture records and otolith-derived age estimates. Three nonlinear length-at-age models were fit to sex-aggregated, tag recapture data and four nonlinear length-at-age models were fit to sex-specific, otolith-derived age data. For each suite of models, model support was determined using Akaike information criteria. The Francis (1988a) GROTAG method had the greatest support of the three models fit to the tag recapture data, and the resulting parameter estimates from the model were...

Alosa alabamae (Alabama Shad) is an imperiled anadromous species that reproduces in northern Gulf of Mexico drainages. To date, there have only been 4 vouchered specimens collected from marine waters, but none have been verified with molecular techniques. On 28 March 2013, we collected a single adult female in proximity to a barrier island (Petit Bois) off the coast of Mississippi. Microsatellite DNA analysis corroborated the identification of this individual and suggested that the specimen was most genetically similar to the group from the Pascagoula River drainage rather than other portions of the range. Thus far, research has been focused on the species' freshwater life history, and it is crucial that more effort be directed toward documenting and understanding the full life history of this threatened fish.

The diverse biological resources in the northern Gulf of Mexico were variably exposed to oil released from the failed Macondo well during the Deepwater Horizon oil spill. In this study, chemical fingerprinting via gas chromatography/flame ionization detection and GC/mass spectrometry [including total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), and petroleum biomarkers] were used to demonstrate novel exposures of four specific resources—Sargassum, deep-sea corals, osprey nests, and dolphin lung tissue. Pelagic Sargassum collected 80 and 170 km from the wellhead during the active spill contained weathered Macondo oil, whereas Sargassum collected 3 to 4 months after the spill showed no chemical evidence of exposure. Deep-sea coral 11 km from the wellhead in late 2010 contained Macondo-derived “oily” floc on its exterior, consistent with its exposure to severely weathered Macondo oil transported as dispersed droplets within the deep-sea plume—and inconsistent with local Biloxi Dome seep oil in the area. Osprey nest materials collected from three nests on Horn Island (Mississippi) in early 2011 contained weathered Macondo oil indicating direct exposure of the occupying adults, and potentially of their eggs or chicks. Finally, lung tissue from a stranded dolphin carcass collected during the spill, which had Macondo oil on its exterior, contained 0.046 μg/g (wet) of decalins and 0.162 μg/g (wet) of PAHs, mostly alkyl-naphthalenes, generally consistent with those predicted (using equilibrium partitioning theory) for the breathing zone vapor phase above moderately evaporated Macondo oil, suggesting inhalation of Macondo oil vapors occurred prior to death.

Since 2011, pelagic Sargassum has experienced extraordinary blooms in the Tropical Atlantic where a system of persistent but seasonally variable currents has retained and consolidated it in large masses. Although beneficial at sea, principally as a unique pelagic habitat, when Sargassum inundates the nearshore environment it can have catastrophic effects on tourism, fisheries, health, and local ecosystems. Providing advanced warning of arrival dates of large masses of Sargassum is critical for enabling preparations and planning for its removal, use, and mitigation. Predictions of arrival time and location involve satellite identification of Sargassum at sea together with ocean current data for forward model tracking. However, forecast ocean current data are generally valid for only 5—7 days. In this study, ocean currents from 2 models (HYCOM and OSCAR) are validated against satellite tracked drifters from the Global Drifter Program with vector correlation and with skill in replicating a drifter pathway. Various wind additions to the models are also tested. Although both models capture the surface current systems in the Tropical Atlantic, they are mediocre in performance along both boundaries. In contrast, a drifter based current data model with 0.5% wind addition had high skill levels. This skill—tested drifter—based model was then used to determine marine connectivity across the Tropical Atlantic and suggests a much broader spread of Sargassum in the eastern Tropical Atlantic than is presently observed by satellites, conforming to earlier hypotheses. This model forms the basis for seasonal scale Sargassum forecasting.

The dusky shark (Carcharhinus obscurus) is the largest member of the genus Carcharhinus and inhabits coastal and pelagic ecosystems circumglobally in temperate, subtropical and tropical marine waters. In the western North Atlantic Ocean (WNA), dusky sharks are overfished and considered vulnerable by the International Union for the Conservation of Nature. As a result, retention of dusky sharks in commercial and recreational fisheries off the east coast of the United States (US) and in the northern Gulf of Mexico is prohibited. Despite the concerns regarding the status of dusky sharks in the WNA, little is known about their habitat utilization. During the summers of 2008–2009, pop-up satellite archival tags were attached to ten dusky sharks (one male, nine females) at a location where they have been observed to aggregate in the north central Gulf of Mexico southwest of the Mississippi River Delta to examine their movement patterns and habitat utilization. All tags successfully transmitted data with deployment durations ranging from 6 to 124 days. Tag data revealed shark movements in excess of 200 km from initial tagging locations, with sharks primarily utilizing offshore waters associated with the continental shelf edge from Desoto Canyon to the Texas/Mexican border. While most sharks remained in US waters, one individual moved from the northern Gulf of Mexico into the Bay of Campeche off the coast of Mexico. Sharks spent 87 % of their time between 20 and 125 m and 83 % of their time in waters between 23 and 30 °C. Since dusky sharks are among the most vulnerable shark species to fishing mortality, there is a recovery plan in place for US waters; however, since they have been shown to make long-distance migrations, a multi-national management plan within the WNA may be needed to ensure the successful recovery of this population.

Digeneans in the genus Hirudinella de Blainville, 1828 (Hirudinellidae) from three species of pelagic fishes, Acanthocybium solandri (Cuvier), Makaira nigricans Lacépède and Thunnus albacares (Bonnaterre), and one benthic fish, Mulloidichthys martinicus (Cuvier), from the Gulf of Mexico are investigated using comparison of ribosomal DNA. Four species are identified based on molecular differences: Hirudinella ventricosa (Pallas, 1774) Baird, 1853 from A. solandri, Hirudinella ahi Yamaguti, 1970 from T. albacares, and two unidentified but distinct species of Hirudinella, herein referred to as Hirudinella sp. A (from both M. nigricans and M. martinicus) and Hirudinella sp. B from M. nigricans. Additionally, H. ahi, based tentatively on morphological identification, is reported from Thunnus thynnus (Linnaeus). This represents the first record of a hirudinellid from M. martinicus and the first record of H. ahi from T. thynnus. A phylogeny of some Hemiurata SkrjabinGuschanskaja, 1954 using partial fragments of the 28S rDNA sequences is consistent with earlier phylogenies and the position of the Hirudinellidae Dollfus, 1932 is well-supported as a derived group most closely related to the Syncoeliidae Looss, 1899.

Despite the circumglobal distribution of scalloped hammerheads, Sphyrna lewini (Griffith and Smith, 1834), little information is available regarding fine-scale movement and habitat use patterns for this species. Over a 27-d period, data were collected on diel habitat use and environmental preferences of a 240 cm (total length) female S. lewini. The shark exhibited a consistent and repeated diel vertical movement pattern, making more than 76 deep nighttime dives; the maximum depth reached was 964 m, where the temperature was 5.8 °C. The purpose of the nightly oscillatory deep diving pattern is unknown but could possibly represent feeding behavior. These findings represent the first detailed account of S. lewini diel vertical behavior and habitat utilization in the western North Atlantic Ocean.

Age validation and estimates of longevity of yellowedge grouper (Epinephelus flavolimbatus) from the Gulf of Mexico (GOM) are needed to inform fishery management decisions. Yellowedge grouper sagittal otoliths (n = 100) were collected, aged using conventional means, and cores were submitted for radiocarbon (14C) measurement. Radiocarbon values of yellowedge grouper otoliths were compared to established radiocarbon chronologies in the region to validate the age and ageing methodology of this species. The yellowedge grouper chronology displayed a similar sigmoidal trend as previously published chronologies. In addition to the core analysis, multiple areas on otolith sections from eight specimens were analyzed for Δ14C to validate age estimates for fish born prior to the 14C increase. Our results indicate that yellowedge grouper live longer than previously reported (minimum of 40 years based on radiocarbon measurements). The validated ageing methodology supported an estimated maximum longevity of 85 years and established that yellowedge grouper have the longest lifespan currently known for any species of grouper in the GOM. Results also indicate a depth-age interaction in that material extracted from adult otolith sections assigned to post-bomb dates exhibited lower Δ14C values than cores (juvenile material) assigned to the same post-bomb dates. This finding is likely explained by lower 14C levels reported from water masses at deeper depths (>100 m) which are inhabited by adults.

The wahoo, Acanthocybium solandri (Cuvier, 1832), is a pelagic, highly migratory, scombroid fish, distributed worldwide throughout tropical and warm temperate seas. To evaluate population genetic and phylogeographic structure against a null hypothesis of panmixia, the entire mitochondrial DNA control-region (~890 base pairs) was sequenced for 231 wahoo. Samples were collected from 1997 to 2001 from seven sites: North Carolina (NC; n=23), east central Florida (CF; n=30), Bimini, Bahamas (BB; n=40), southern tip of Florida (SF; n=21), Cayman Islands (CI; n=23), northern Gulf of Mexico (NG; n=54), and Hawaii (HI; n=40). Inter-annual samples were obtained from four of these locations (NC, BB, SF, NG). Seventeen haplotypes were shared by individuals within and among samples; 187 singleton haplotypes were observed. Within-sample haplotype diversities ranged from 0.995 to 1.000 (overall h=0.999) and within-sample nucleotide diversities ranged from 0.049 to 0.055 (overall π=0.053). A neighbor-joining tree based on inter-haplotypic distances revealed two monophyletic lineages differing by 13.6% nucleotide divergence. Nested within each major lineage were several, well-supported subclades. There was no evidence of temporal heterogeneity in haplotype distributions. Partitioning mtDNA variation, 99.75% of the variance was within samples and 0.25% (P=0.307) between samples; the fixation index (ΦST=0.0025) was not significant. Likewise, pairwise ΦST values were low or negative, and none were significant on a table-wide basis. Exact tests for sample differentiation in haplotypes were also non-significant. All population analyses were consistent with the null hypothesis of panmixia. However, analytical power was limited by sample size. Mismatch distributions were inconsistent with expected distributions based on sudden-expansion and static-growth models. Wahoo exhibit concurrently high haplotype and nucleotide diversities, presumably a consequence of secondary contact between historical subpopulations rather than a long, stable evolutionary history. Given the level of geographic and individual sampling, wahoo thus far represent the sole example of a scombroid or xiphioid fish exhibiting coarse-grain genetic homogeneity across a broad, inter-oceanic range despite a deeply coalescing genealogical structure. Accordingly, cooperative fishery management on a broad, inter-ocean scale may be warranted.

The Tripletail, Lobotes surinamensis, is a pelagic fish found in tropical and sub-tropical waters of all oceans. Tripletails are often associated with floating debris and make frequent incursions in bays and estuaries where they are targeted by recreational fishermen. In Mississippi waters the species is typically present during the late spring and summer season that also correspond to the period of sexual maturation and spawning (Brown-Peterson and Franks 2001). Tripletail is appreciated as a gamefish but is also prized for its flesh of superior quality. The fast growth rate of juveniles in captivity documented by Franks et al. (2001) and the excellent quality of Tripletail flesh both contribute to the potential of this species for marine aquaculture. In addition, the production of cultured juveniles would be precious to develop a better understanding of the biology, early life history and habitat use of Tripletail larvae and juveniles, a topic largely undocumented to date, through experimental releases and controlled studies. The culture of tripletail thus supports the Tidelands Trust Fund Program through improved conservation of natural resources, potential enhancement of fisheries productivity and potential development of a new economic activity on the Gulf coast producing tripletail via aquaculture. The Objective of this project was to initiate development of methods and techniques needed to spawn captive held tripletail broodfish and raise their offspring to evaluate their growth and development in captivity. In this report we will present the results of studies aiming to develop methods and protocols for captive spawning of tripletail and the first data obtained on the early development of tripletail larvae. A major issue that was encountered with tripletail broodstock development during the project lied in the difficulties associated with identifying the sex of adults caught in the wild and candidates for being incorporated in mating sets for spawning. This issue was addressed during the course of the project by examining the potential of a non-lethal method of hormonal sexing. The results of these preliminary investigations are presented in the third part of this report. All protocols used in the project were determined with the guidance of the Institutional Animal Care and Use Committee (IACUC) of the University of Southern Mississippi (USM IACUC protocol number 10100108).

Background: Reports of whale sharks (Rhincodon typus) in the northern Gulf of Mexico (GOM) date back to the 1930s. In 2003, the Northern Gulf of Mexico Whale Shark Research Program was established and began making directed efforts to document the regional occurrence, seasonal distribution and habitat preferences of whale sharks. Methods: Whale shark sightings data (WSS: 1989 – present; n=644) and tagging geoposition data (TD: 2009-2012; n=450) were used in seasonal kernel density (KD) analyses to delineate home range (95%) and core habitat (50%) use areas in the northern GOM. Kernel density estimation of distribution is a statistically robust manner of handling data sources with differing sampling designs (anecdotal vs. directed). Habitat use patterns from the two datasets were used to identify critical use areas. Results: In the study area, whale shark home range was 276,000 km2 (WSS) to 369,000 km2 (TD) in size, with 52,000 km2 (WSS) to 62,000 km2 (TD) being core habitat. Whale shark habitat use varied seasonally, with the largest home range occurring during summer (WSS: 213,000 km2) and fall (TD: 221,000 km2). Tag data revealed more winter habitat (75,000 km2) than the sightings dataset (41,000 km2), which was shifted further offshore to slope waters. Significant use patterns occurred along the continental shelf-edge, encompassing shelf-edge banks south of Louisiana, and near the mouth of the Mississippi River. Conclusions: The combination of sightings data and satellite tagging data represents an effective methodology for assessing seasonality of occurrence, distribution, and habitat use of whale sharks. Shelf-edge bank habitats were most commonly used by whale sharks in the region. Satellite tagging data provided additional evidence of connectivity between multiple jurisdictions, which lends support for international management of the species.

Background: The Northern Gulf of Mexico Whale Shark Research Program was initiated in 2003 to increase our knowledge of whale shark occurrence and distribution within the region. A primary goal was to obtain sightings data from “citizen scientists” to guide directed research. Whale sharks are typically solitary animals, but are known to aggregate in areas of high prey abundance. Methods: Whale shark sightings data reported from 2003 to present were compiled. Aggregations were defined as more than one whale shark, and large aggregations were defined as 10 or more sharks, observed at a specific location at the same time. Efforts were made to encounter aggregations to determine size and sex assemblage of the sharks, and to collect plankton samples to identify potential prey. Results: To date we have over 600 whale shark sightings reports and four research encounters of large aggregations. Whale shark aggregations represented 31% of reported sightings, 25% of which were large aggregations between 10-150 individuals. All of thereported large aggregations occurred during summer, almost exclusively along the continental shelf edge, with 41% occurring at Ewing Bank. Three out of the four scientific encounters occurred at Ewing Bank (2009, 2010, 2013). Aggregations were dominated by immature males that were primarily feeding on Euthynnus alletteratus eggs. Conclusions: The use of sightings data provided by “citizen scientists” has proven to bean inexpensive and effective technique for identifying whale shark aggregation locations in the northern Gulf of Mexico. Aggregation assemblages appear to consist of largely juvenile males that were feeding on tuna eggs. Similar to other regions, it is unknown if whale sharks in the northern Gulf of Mexico primarily consist of juveniles or if juveniles simply dominate these large feeding aggregations.

William Stein III1*, Nancy J. Brown-Peterson2, James S. Franks3, and Martin T. O’Connell1 Nekton Research Laboratory, Pontchartrain Institute for Environmental Sciences, University of New Orleans, 2000 Lakeshore Dr., New Orleans, LA 70148, USA; Department of Coastal Sciences, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, USA; and Gulf Coast Research Laboratory, The University of Southern Mississippi, 703 East Beach Dr., Ocean Springs, MS 39564, USA; *Corresponding author email: wstein@uno.edu SHORT COMMUNICATION

Studies toward the development of cobia ( Rachycentron canadum ) aquaculture were initiated. Methods of cryopreserving cobia sperm were compared and sperm motility was assessed after longterm frozen storage. Sperm stored in 10% dimethyl sulfoxide, 3 mM glucose, and 10% raw chicken egg yolk showed approximately 100% motility upon thawing after more than 1 year of storage at −80°C. Sperm motility declined after about 60 min at room temperature, but approximately 100% motility could be restored by addition of a few drops of 5 mM theophylline. Ripe, wild-caught female cobia were held in recirculating seawater systems and ovulation was induced by injection of human chorionic gonadotropin at a concentration of 275 IU/kg of body weight. Fertilization was attempted using the cryopreserved sperm. Although fertilization did not occur, we are optimistic that cobia aquaculture is feasible.

The first documented occurrence of a basking shark, Cetorhinus maximus, in the Gulf of Mexico was reported off Sarasota, Florida in 1969 and was considered peculiar as the species is considered to be limited to cold water habitats. Recently, four separate sightings of individual basking sharks within the northern Gulf of Mexico have occurred indicating the species, while not common, might not be as rare in the region as once considered. All four sightings occurred in shallow coastal waters off northern Florida during March of 2010, 2011. Analyses of satellite imagery indicated that the presence of basking sharks in north-eastern Gulf of Mexico waters coincided with an intrusion of oceanic Loop Current waters into coastal waters.

On 26 June 2006 an aggregation of 16 whale sharks was observed for a period of 4 hr in the north central Gulf of Mexico (GOM). The sharks remained within an area about 1.0 km 2 in size and continuously ram filter fed at the surface. Visual analysis of a plankton sample collected from the study site revealed the presence of copious amounts of fish eggs in mid-embryonic development and a minor amount of other zooplankton. A second plankton sample (control) collected about 3.5 km from the study site in an area where no whale sharks were pres- ent contained few eggs, however other zooplankton were similar to the study site sample in species composition and abundance. Two egg morphs were identified, and samples of one of the morphs, which represented 98% of the eggs at the study site, were verified by genetic analysis as little tunny, Euthynnus alleteratus. The observed feed- ing behavior and the abundance of fish eggs at the study site indicated the whale sharks were feeding on recently spawned little tunny eggs. This represents the first confirmed observation of a feeding aggregation of whale sharks in the GOM.

The whale shark (Rhincodon typus Smith, 1828) is the world’s largest fish, reaching 15 meters (m) and 18 metric tons (Colman 1997) and is found in all tropical and warm temperate seas (Compagno 2001). The whale shark is listed as ‘vulnerable’ by the International Union for the Conservation of Nature and Natural Resources (IUCN 2004) and is included in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES 2004). Little is known about whale sharks in the Gulf of Mexico (Gulf). Only reports on the occurrence of whale sharks off Texas (Baughman 1950, Baughman and Springer 1950, and Hoffman 1981) and accounts of the occurrence and feeding in the northcentral Gulf (Gudger 1939, Springer 1957) are available. Due to the lack of information on whale sharks in the Gulf, we developed a survey (http://www.usm.edu/gcrl/whaleshark_survey) to compile records of recent sightings and associated observations that are summarized here.

Early-juvenile tripletail Lobotes surinamensis (n = 27; range 45-115 mm TL, 0 = 73.0 mm; range 3.2-34.7 g TW, 0 = 12.9 g) captured in pelagic Sargassum algae off coastal Mississippi in mid-July 1999 were reared in a recirculating seawater system for 210 days. Fish were maintained on a natural light-dark cycle and fed to satiation 3 times per day. Water temperature ranged from 25.2° to 29.0° C and salinity was 28.0‰. All fish were measured for length and weight on days 1, 60, 135 and 210 of the study. Between these dates, mean daily TL growth rates were 2.2 mm/day, 1.2 mm/day, and 1.0 mm/day, respectively, where as 0 daily TW growth rates were 2.9 g/day, 4.3 g/day, and 7.1 g/day. Over the entire study, 0 TL and TW growth rates were 1.4 mm/day and 4.9 g/day, respectively. There was a significant correlation between length and weight vs. date of measurement. At the end of the study, specimens ranged from 272-431 mm TL (0 = 359 mm) and from 443.9-2,380.0 g TW (0 = 1,012.5 g).

Stomach contents analysis was used to quantitatively describe the diets of juvenile lane snapper, Lutjanus synagris, and juvenile gray snapper, Lutjanus griseus, from the northern Gulf of Mexico. Juvenile snapper were collected by trawling at two estuarine, deep channel sites in Mississippi coastal waters from September 1996 to January 1997. Lane snapper (n = 53) and gray snapper (n = 12) both consumed a variety of prey organisms, but primary prey were amphipods, decapods (shrimp and crabs), and fishes. The most important prey items for lane snapper based on percent Index of Relative Importance (%IRI) were shrimp remains (44%IRI), the shrimp Latreutes parvulus (23%IRI) and fish remains (13%IRI). Fishes of the genus Anchoa (43%IRI), shrimp remains (21%IRI) and the amphipod Corophium sp. (13%IRI) dominated the gray snapper diet. Intraspecific comparisons of lane snapper diet revealed significant overlap between collection sites, seasons and fish sizes.

A synchronous hermaphroditic striped mullet, Mugil cephalus, was captured offshore of Southwest Pass, Louisiana on 6 December 1996 during the commercial roe mullet fishery harvest. The fish measured 412 mm FL, weighed 824 g and was determined to be 4 years old by otolith analysis. Gross examination of the gonads revealed four lobes: right and left ovaries and right and left testis which represents a unique occurrence among hermaphroditic fish. All lobes ended in a common sperm duct/oviduct with the exception of the left ovary which had no oviduct. Both ovaries contained vitellogenic oocytes and both testis had freely running spermatozoa. Histological examination showed many oocytes undergoing final oocyte maturation, the presence of some post ovulatory follicles and lobules full of tailed spermatozoa. There was no evidence of the intermingling of sperm and oocytes within the gonad. The capture of this fish on the spawning grounds and the advanced stage of both ovarian and testicular development suggests spawning probably would involve the release of both oocytes and spermatozoa.

The stomach contents of 403 cobia, Rachycentron canadwn, caught in the northcentral Gulf of Mexico recreational fishery from April through October of 1987-1990 were examined. Cobia ranged from 373-1,530 mm in fork length. Of the 403 stomachs, 287 (71.2%) contained at least one identifiable prey taxon. Crustaceans, consisting primarily of portunid crabs, were the predominant food. Crustaceans occurred in 79.1% of the stomachs and comprised 77.6% of the total number of identifiable prey. The second most important prey categoy was fish which was dominated by hardhead catfish, Arius felis, and eels. Fish occurred in 58.5% of the stomachs but only accounted for 20.3% of the total number of prey. The importance of fish as prey increased withincreasing size(length)ofcobia, with thelargest sizeclassofcobia(1,150-1,530mmFL)showingthehighest percent frequency occurrence of fish prey (84.4%). There were no significant differences between the diets of male and female cobia. Species composition of the diet indicated that cobia examined in this study were generalist carnivores in their feeding habits and fed primarily on benthic/epibenthic crustaceans and fishes. However, the Occurrence of pelagic prey provided evidence of diversity in the foraging behavior of cobia. Feeding in cobia indicated their dependence upon prey availability rather than upon a few specific food organisms.

Gonadal maturation of cobia, Rachycentron canadum, was evaluated by examining 508 specimens from its recreational fishery. Specimens were collected off southeast Louisiana to northwest Florida by hook-and-line during February through October 1987-1991. Fork lengths (FL) of these fish ranged from 580-1,530 mm, with corresponding weights of 2.0-43.5 kg. The female:male ratio was 1:0.37. Using a combination of oocyte sizefrequency and histological assessment of many of the fish, we determined that females were ripe from May through September, with atretic oocytes occurring in some fish from July through October. Degenerating hydrated oocytes in July and October and the presence of resting ovaries in July suggest two major spawning periods; however, monthly gonosomatic indices peaking in May, followed by a steady decline, do not support that finding. Ovaries were placed into undeveloped, early developing, mid-developing , or late developing categories based upon oocyte size-frequency distributions. Developing ovaries had two or three modes of oocytes larger than 30 pm. Batch fecundity was estimated to be 2 . 6 ~ 1 0 ~ to 1.91~108 oocytes, depending on the size of fish/ovaries. The smallest female with oocytes exhibiting vitellogenesis was 834 mm FL. This fish was 2 years old based its otolith evaluation. The smallestmale with an abundance of spermatozoa in its testes was 640 mm FL and 1 year old based on otolith evaluation; smaller males were not examined. Females larger than 840 mm FL had vitellogenic oocytes in March and April. A few fish still had vitellogenic oocytes in early October, but none did by late October. When Gilson’s fluid was used to assess ovarian tissue, the fresh weight of the tissue was reduced by 20% after being stored for 3 months. The diameter of oocytes shrunk about 25% in Gilson’s fluid which was 11% less than those fixed in formalin, embedded in paraffin, and sectioned. Tissue sections from specific individuals, each demonstrating a variety of different developmental stages, were similar regardless of whether they were obtained from the anterior, middle, or posterior portion of either ovary.

Apugheaded cobia (Rachycentron canadum) captured in the northcentral Gulf of Mexico represents the fist record of pugheadedness in cobia. The specimen, a 4-year-old gravid female, exhibited considerable distortion of the premaxillary and maxillary bones, with the length of the snout 46% shorter than that of a normal cobiaof the same length. The anomaly had no apparent effect on feeding, since the stomach contained a substantial amount of food, and the fish was the same length expected of a normal 4-year-old cobia.

An investigation to ascertain the species composition and the relative abundance of the fish population within the inland waters of Horn Island, Mississippi, a member of the offshore barrier island chain, was made from August 1965 to September 1966, and 69 species representing 58 genera and 35 families were encountered. In respect to the fishes certain biological and physical factors were noted. Forty-nine collecting stations were established on the island, and these were categorized according to the nature of their appearance and location. A salinity range from fresh to 29.9 ppt. was recorded for the sampled bodies of water, with the high salinity areas being under the influence of Mississippi Sound waters. Fishes with both marine and brackish water affinities were collected. Euryhaline species were taken from both fresh water and water which was approaching fresh; however, no true fresh water fishes were obtained. Members of the Atherinidae, Cyprinodontidae, and Poeciliidae (Menidia beryllina, Cyprinodon variegatus, Fundulus similis, Gambusia affinnis, and Poecilia latipinna) contributed most conspicuously to the fish population. Other families which were encountered formed somewhat less conspicuous elements in the population. The killifishes and poeciliids are capable of completing their life histories in the majority of examined areas, and these species contributed most obviously to the permanent occupancy of the inland waters due to their established resident breeding populations.