Multivariate evaluation of life history strategies (LHSs) for fish species have a number of implications for population dynamics and viable management strategies. Here we examined intraspecific variation in LHSs among black drum (Pogonias cromis) populations, with focus on a population inhabiting the Upper Laguna Madre, Texas (a hypersaline estuary). Age, growth, and reproduction for this population were analyzed in the context of previously published life history data for this and other black drum populations along the western Atlantic and Gulf of Mexico coasts. Black drum from the Upper Laguna Madre were found to mature earlier than other populations. When analyzed in the context of other life history variables (fecundity, maximum age, maximum size, and growth rate) and compared to other populations of black drum throughout their range, LHS in the Upper Laguna Madre population was found to diverge away from the typical periodic LHS of sciaenids and towards the opportunistic side of the multivariate LHS spectrum. This variation in LHS is often indicative of populations existing in habitats that are productive yet subject to frequent and intense disturbance. Here, this disturbance is attributed to hypersalinity that has historically characterized the Upper Laguna Madre. This variation in LHS is further supported by observed population dynamics for this region presented in past work and has a number of potential management implications for this population.

Atlantic croaker (Micropogonias undulatus) are one of the more common finfishes in the Gulf of Mexico. They are a significant component of Gulf bait fisheries and an important midtrophic component of nearshore food webs. In this study, life-history parameters associated with growth, maturity, and seasonal migration were estimated for Atlantic croaker in Texas and integrated into previously described data throughout the rest of the species range. The major findings of this work were the following: (1) a majority (>76%) of age-1 female Atlantic croaker were sexually mature; (2) egress of adults from inshore habitats took place in late fall (Oct./Nov.) in consecutive years (2002 and 2003); (3) egress of adults was predictably coincident with declining growth after age-1 and the onset of sexual maturity; and (4) ingress of juvenile Atlantic croaker into inshore nursery grounds began in early winter and progressed through early summer, but a majority of recruits appeared in a short span between Feb. and April. Seasonal patterns of migration of both adult and juvenile Atlantic croaker are consistent with those described in other parts of the species' range and imply offshore spawning in the fall and winter followed by year-round inshore development of postlarvae and juveniles. Given the importance of inshore residency of juvenile Atlantic croaker, abundance estimates from fishery-independent sampling were scaled up to system-wide estimates of juvenile abundance in two prominent Texas estuaries and used to qualitatively assess the potential impacts of the commercial fishery on the inshore segment of the population.

As part of a stock enhancement program in Texas, Red Drum Sciaenops ocellatus are subject to a standard salinity acclimation protocol between the hauling trailer and stock site of 1 h per 10 parts per thousand salinity difference. In certain circumstances (hypersaline sites or drought) salinity differences can exceed 20 parts per thousand between hauling trailer and stock site. Information is needed on whether the current protocol is sufficient to investigate whether extending the acclimation time can improve survival. We conducted nine trials, each exposing pond-cultured Red Drum fingerlings to salinity increases of 10 parts per thousand (over 1, 2, and 3 h), 20 parts per thousand (over 2, 4, and 6 h), and no salinity change (control). Survival at 96 h following a change in salinity of either 10 parts per thousand or 20 parts per thousand was independent of the rate of increase in salinity. However, survival was lower among Red Drum subjected to an increase of 20 parts per thousand (survival, 61%) than to 10 parts per thousand (82 parts per thousand). Fish condition, length and weight of fish examined here had no significant effect on survival, across trials. Results suggest that hatchery personnel should select stocking sites within 10 parts per thousand salinity of the production pond and hauling trailer.

To determine the minimum age/size at which Southern Flounder, Paralichthys lethostigma, can safely be moved to outdoor rearing facilities in Texas, we examined survival of simulated temperature drops in two distinct life stages: premetamorphic larvae and two size classes of postmetamorphic juveniles (small = 9.8 ± 0.3 mm in TL; large = 19.7 ± 0.6 mm). Temperature was lowered by −0.33°C/h to 4°C, 7°C, or 10°C, held for 48 h and then raised at +0.33°C/h back to normal rearing temperature. Fish were monitored daily for survival. Larger postmetamorphic flounder had high survival for all temperature treatments (89%–100% survival), whereas both premetamorphic larvae and smaller postmetamorphic juveniles had low survival (<30%) for all temperature treatments.

Previous work investigating the temperature tolerance of juvenile red drum ranging 18–50mm TL found evidence for positive size dependence (smaller fish less tolerant to higher temperatures) suggesting smaller size classes (<18mm TL) potentially may succumb to extreme summer water temperatures. Here, we explored the upper lethal temperature tolerance (ULT) in smaller-sized red drum which ranged from 10 to 20mm TL across multiple salinities to further understand the thermal limitations of this propagated game fish. In order to investigate the combined effect of temperature and salinity on ULT, temperature trials were conducted under three levels of salinity which commonly occur along the coast of Texas (25, 35, and 45ppt). The rate of temperature increase (+0.25°C/h) was designed to mimic a natural temperature increase of a summer day in Texas. We determined that the lethal temperature at 50% (LT50) did not differ between the three salinities examined statistically; median lethal temperature for individuals exposed to 25ppt ranged from 36.4 to 37.7°C, 35ppt ranged from 36.4 to 37.7°C, and 45ppt ranged from 36.1 to 37.4°C. Further, LT50 data obtained here for early-juvenile red drum did not differ from data of a similar experiment examining 25mm TL sized fish.

The critical thermal maximum of juvenile spotted seatrout (SL range 18–33 mm) was determined using a temperature increase of +0.26°C per hour. The critical thermal maximum (water temperature that was lethal to 50% of the test fish [LT50]) for trial 1 was LT50 = 38.8°C, LT50 = 39.4°C for trial 2, and LT50 = 38.9°C for trial 3. Critical thermal maximums differed significantly (P < 0.05) between trials 2 and 3, whereas trial 1 did not differ among trials. This difference correlated with body size, where fish in trial 2 were significantly larger (P < 0.05) (mean = 27.6 ± 2.0 mm in SL) (mean ± SE) than the fish of trials 1 (mean = 23.1 ± 0.5 mm in SL) and 3 (mean = 21.5 ± 0.7 mm in SL), suggesting positive size dependence in the critical thermal maximum.

The Alligator Gar Atractosteus spatula is currently imperiled due to habitat alterations and overharvest within much of this species' range. Recent interest in improving management for this species within the USA and Mexico has spurred new creel restrictions, spawning area closures, and stocking programs, along with increased research on life history and population dynamics. These management and research measures can be improved by a noninvasive method for determining sex. Previous methods have required sacrificing the fish (for internal anatomy confirmation) or using costly and time-consuming assays from a specialized laboratory. Evidence from other gar species suggests that sex determination is possible by examining sexually dimorphic external characters. We evaluated the utility of 13 morphological measurements for determining the sex of Alligator Gars of known gender (n = 117; SL range, 591-1,255mm). Discriminate analysis identified two influential variables (snout length and caudal peduncle height) as sexually dimorphic. Univariate analyses identified three variables as sexually dimorphic (head length, snout length, and anal fin base length). Sexually dimorphic variables were used with SL to develop a method using serial body ratios (SL/snout length) followed by (snout length/anal fin base length) to identify sex in Alligator Gar to 93% accuracy in males and 72% accuracy in females.

Spatial and temporal variation in recovery of hatchery-released red drum (Sciaenops ocellatus) was assessed in nine bays and estuaries along the Texas coast. Sixteen nuclear-encoded microsatellites were used to identify a total of 167 hatchery-released fish among 4325 red drum sampled between the fall of 2006 and the spring of 2009; these were added to 41 recovered hatchery-released fish identified in a prior study of 1332 red drum sampled from Galveston and Aransas bays in the fall of 2005 and spring of 2006. Recovery of hatchery releases across bays and years ranged from 0.28% to 17.65%. Of the 208 recovered hatchery-released fish, 158 were age 0–1, 46 were age 1–2, and four fish were age 2–3. The distribution of recovered hatchery-released fish and wild fish differed significantly across sampling periods within and among bays or estuaries. Allelic richness in recovered hatchery-released fish was significantly lower than in both hatchery brood fish and wild fish. In addition, recovered hatchery-released fish were produced by fewer dams, sires, and dam×sire combinations in 2005 and 2006 and by fewer dams and sires in 2007 than would be expected if reproductive success was distributed randomly among brood fish. The spatial distributions of recovered hatchery-released and wild fish deviated from random expectations for samples from the Upper Laguna Madre in the fall of 2006 and spring of 2007 and from West Matagorda Bay in the spring and fall of 2008. Correlation and principal components analysis identified a significant, positive relationship between annual average CPUE and relative annual mortality. No relationship was observed between the number of fish released per hectare and the percentage of recovered hatchery-released fish. Comparisons to other studies of red drum stock enhancement are discussed.

Abstract Hatchery-propagated red drum Sciaenops ocellatus are released by the Texas Parks and Wildlife Department (TPWD) during the spring, summer, and fall to supplement natural stocks. Reported success of red drum stocked out of season in summer has been low or nonexistent; several potential causes, including mortality due to high temperatures, have been suggested. The present study was devised to determine the critical thermal maximum (CTM) of pond-raised juvenile red drum that had previously been exposed to diurnal temperatures of the summer season. Laboratory studies designed to mimic the rate of temperature increase (0.25°C per hour) typical of TPWD rearing ponds were used to examine rates of mortality in juvenile red drum that were collected from three separate ponds exposed to the ambient fluctuating temperatures of the summer season. The CTM (temperature that was lethal to 50% of the test fish [LT50]) was significantly lower (P < 0.0001) for two of the fish trials (LT50 = 37.1°C and 37.0°C) than for a third trial (LT50 = 38.7°C). This difference correlated with the size of fish in each trial; the two trials with smaller-sized fish (range = 18–32 mm total length) had the lower CTMs, whereas the trial with larger-sized fish (range = 31–50 mm total length) had the higher CTM, suggesting positive size dependence in the CTM. The CTMs obtained here are higher than the maximum temperatures encountered in grow-out ponds during summer, indicating that high temperature exposure may not be the sole cause for the low success of red drum stocked out of season.

Cobia are a migratory marine species that have recently gained popularity as foodfish in the aquaculture market and for stocking. Unfortunately, when culturing these species, aquaculturalists may unknowingly expose these fish to temperature extremes not normally experienced in situ. We set out to test for the critical thermal minimum temperatures of juvenile cobia by exposing them to a simulated freeze, at a drop rate of 0.33°C per hour. We observed and documented behavioral effects due to low temperature exposure using criteria for loss of equilibrium and death. We determined that the median temperature for loss of equilibrium was 12.1 ± 0.40°C and the median lethal temperature was 9.7 ± 0.28°C for low temperature tolerance. We recommend that precautions be taken well before water temperatures reach 13°C in a freeze scenario.

Sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) are both found within the immediate offshore areas of the Gulf of Mexico, especially around Texas; however information is limited on how much distributional overlap really occurs between these species. In order to investigate spatial and seasonal differences between species, we analyzed twenty years of bay and offshore trawl data collected by biologists of the Coastal Fisheries Division, Texas Parks and Wildlife Department. Sand seatrout and silver seatrout were distributed differently among offshore sampling areas, and salinity and water depth appeared to correlate with their distribution. Additionally, within the northernmost sampling area of the gulf waters, water depth correlated significantly with the presence of silver seatrout, which were found at deeper depths than sand seatrout. There was also an overall significant decrease in silver seatrout abundance during the summer season, when temperatures were at their highest, and this decrease may have indicated a migration farther offshore. Sand seatrout abundance had an inverse relationship with salinity and water depth offshore. In addition, sand seatrout abundance was highest in bays with direct passes to the gulf and correlated with corresponding abundance in offshore areas. These data highlight the seasonal and spatial differences in abundance between sand and silver seatrout and relate these differences to the hydrological and geological features found along the Texas coastline.

The stock enhancement program for red drum Sciaenops ocellatus in Texas annually releases from 25 to 30 million fingerlings into Texas bays and estuaries and represents one of the largest such programs for marine fishes worldwide. We used 16 nuclear-encoded microsatellites and a 370-base-pair fragment of the mitochondrial DNA (mtDNA) D-loop to assign red drum sampled from two bays along the Texas coast to either hatchery or wild origin. A total of 30 hatchery-released fish were identified among 321 red drum belonging to three year-classes sampled from Galveston Bay, while a total of I I hatchery-released fish were identified among 970 red drum belonging to four year-classes sampled from Aransas Bay. Allelic richness (microsatellites) was significantly lower among hatchery-released fish than among hatchery broodfish and wild fish. Similarly, the expected number of mtDNA haplotypes in hatchery-released fish (based on simulation analysis) was significantly lower than that expected in a random sample of both brood and wild fish. The contribution of brood dams, sires. and dam X sire combinations to the hatchery-released fish was nonrandom, as was the distribution of hatchery-released and wild fish with respect to sampling stations (localities) within each bay. The possibility of a Ryman-Laikre effect is discussed.

The sand seatrout (Cynoscion arenarius) and the silver seatrout (C. nothus) from the family Sciaenidae are sympatric species that co-occur within the Gulf of Mexico (GOM). In the literature, the co-occurrence and distribution of these species has been noted, particularly in offshore areas where feeding grounds overlap (Miller, 1965; Chittenden and McEachran, 1976). These studies, in concert with previous life history data from Texas (Shlossman and Chittenden, 1981; DeVries and Chittenden, 1982) have provided some insight into when and why any distributional variation occurs in the western GOM. Nevertheless, most studies of the abundance of these species have been limited on a spatial and temporal scale. Additionally, the spatial and temporal abundance of these species in relation to hydrological characteristics such as water temperature, salinity, depth, and bay access to the gulf through a channel or pass has not been thoroughly investigated. Sand seatrout use inshore waters extensively but also move offshore seasonally to evade the temperature extremes of the inshore bays and to spawn (Shlossman and Chittenden, 1981; Vetter, 1982). In contrast silver seatrout, although on occasion they can be collected inshore, live their entire lives offshore (Gunter, 1945; Miller, 1965). In addition to their distributional difference, differences exist in their hydrological preference, particularly in salinity and water depth, adding to the complexity of the distributional preferences of these two species (Chittenden and McEachran, 1976). However, a great deal of distributional overlap of these species occurs within the immediate offshore area, year-round (Gunter, 1938; Sheridan et al., 1984), although the spatial and temporal dynamics of this overlap are poorly understood. Furthermore, information is limited on whether the distribution of sand seatrout offshore correlates with what is found inshore (bays) (Shlossman and Chittenden, 1981). Each of the bays along the Texas coastline is unique in their geological and hydrological characteristics, giving rise to differences in species assemblages between the bays (Blackburn, 2004). Spatial and seasonal abundance of sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) off the coast of Texas, determined with twenty years of data (1987–2006)

Experiments were conducted to determine the effect of the salt-box catch-bycatch separation procedure, as used by the Texas shrimp industry, on short-term survival of bycatch. Bioassays were conducted on five economically important bycatch species: spotted seatrout (Cynoscion nebulosus); red drum (Sciaenops ocellatus); Atlantic croaker (Micropogonias undulatus); southern flounder (Paralichthyes lethostigma); and blue crab (Callinectes sapidus). Red drum were most affected by hypersalinity, requiring 17 minutes exposure to a 70 parts per thousand salt water solution to kill 50% of the test specimens within 48 hours. For samples collected from commercial boats and Texas Parks and Wildlife (TPW) trawl samples, we found that neither initial nor final percent survival was significantly different for bycatch removed with or without the aid of a salt-box, Bycatch mortality was high regardless of the method used to separate bycatch from the target catch, At the conclusion of catch separation, bycatch survival averaged 76% (+/- 22%) for commercial samples and 48% (+/- 40%) for TPW trawl samples separated with salt-boxes. Survival at the conclusion of catch separation without a salt-box averaged 56% (+/- 35%) for commercial samples and 43% (+/- 39%) for TPW trawl samples. Bycatch survival 21-27 h after catch separation averaged 13% (+/-6%) for commercial samples and 5% (+/-9%) for TPW trawl samples separated with salt-boxes and 34% (+/- 29%) for commercial samples and 10% (+/- 19%) in TPW trawl samples separated without a salt-box. Mortality rates (AT) for bycatch separated with a salt-box averaged 0.08 (+/-0.03) for commercial samples and 0.10 (+/-0.04) for TPW trawl samples. For bycatch separated without the salt-box, M averaged 0.48 (+/-1.23) for commercial samples and 0.10 (+/-0.05) for TPW trawl samples. Results of an exploratory analysis with stepwise multiple regression suggested that final percent survival of bycatch was most affected by trawling time. The salt-box had little or no effect on bycatch survival; therefore, regulating the use of salt-boxes in shrimp trawling operations is not necessary.

Stocking with red drum (Sciaenops ocellatus) fingerlings (25-30 mm TL) and conventional strategies for reduction of fishing mortality are major components in the fisheries management philosophy of Texas. Texas studies reveal high red drum survival 24 h after stocking and detection of some stocked fish in subsequent years. Beginning in 1994, three additional studies were implemented to assess survival of stocked red-drum fingerlings: (I) lengths of red drum caught in spring gill nets in stocked bays were compared with those from an unstocked bay by length-frequency analysis; (2) relationships between releases and subsequent relative-abundance indices were explored by regression analysis; and (3) fingerlings (25-35 mm TL) marked with oxytetracycline-HCl were released into selected bays for studies of the feasibility of monitoring stocked fish by means of ongoing monitoring programs. These and previous studies reveal variable survival of stocked red drum across locations, bays, times, and years. Preliminary length-frequency analyses reported here indicate that both survival of out-of-phase (spring) stocked fingerlings and increases in red drum relative abundance through the first 2 yrs of life may reach 21% in some Texas bays.

In 1983, the Texas Parks and Wildlife Department initiated a stock enhancement program that released up to 20 million red drum Sciaenops ocellatus annually. To evaluate the contribution of hatchery production to the fishery, scale pattern analysis was used to differentiate between hatchery-reared and wild fish. Scale patterns from 30-150-d-old hatchery-reared red drum fingerlings (13-35 mm total length, TL) from two hatcheries and wild red drum juveniles (<121 mm TL) were analyzed to establish a linear discriminant function. Accurate identification of 30-d-old hatchery-reared red drum ranged from 61-64%, but decreased to 35% for 60-150-d-old fish: classification rates for wild fish ranged from 63% to 70%. Correct classification of 30-d-old hatchery Bsh was significantly better than chance, but correct classification of wild fish was only significantly better than chance at one hatchery. Linear discriminant functions were used to evaluate variation between spring and fall hatchery-reared red drum and wild red drum. Correct identification ranged from 41% to 77% for spring fish, from 43% to 63% for fall fish, and from 38% to 54% for wild fish. Classification of spring and fall fish were significantly better than chance at both hatcheries, but classification of wild fish was significantly better than chance at only one hatchery. Scale pattern analysis was effective at differentiating between hatchery and wild fish but was not as effective at separating seasonally produced hatchery-reared fish and wild fish.

Acute toxicities of oxytetracycline hydrochloride (OTC) and calcein to juvenile striped bass Morone saxatilis (48 +/- 5 mm total length) were determined by immersion. Fish were held in test solutions for 6 h, then placed in clean water and observed for 96 h postexposure. Both OTC and calcein bind to calcium and fluoresce under ultraviolet light, which makes them useful for marking bony structures of fish. Information on toxicity of these chemicals to juvenile striped bass will help establish maximum concentrations that can be used to mark hatchery fish stocked for population enhancement or establishment. The no-observed-effect concentration (NOEC), 96-h LC10, and LC50 (concentrations lethal to 10 and 50% of test fish) values for the 6-h chemical exposure were 447, 322, and 597 mg/L for OTC and 125, 160, and 240 mg/L for calcein.

Based upon isoelectric focusing, this study reports the natural occurrence of a Morone saxitilis x M. mississippiensis hybrid as well as an individual specimen which is interpreted to be the product of a hybrid (probably M. chrysops x M. saxatilis) crossing with a member of a third species (M. mississippiensis).