Florida bass Micropterus floridanus are endemic to peninsular Florida and co‐occur with largemouth bass M. salmoides in a natural intergrade zone in the northern portions of the state. In this study, we resolved the genetic population structure among populations of largemouth bass, Florida bass, and their interspecific hybrids from 48 lakes and streams across Florida, and we updated and refined the southernmost boundary of introgression. Nuclear (allozyme and microsatellite) and mitochondrial (restriction fragment length polymorphism) markers produced somewhat different results. Microsatellite genotypes alone and the combination of all nuclear genotypes resolved genetic structure among four regional groups within Florida: (1) northwest, (2) north‐central, (3) central‐west, and (4) south, central‐east, and northeast. Allozyme genotypes alone did not resolve well‐defined groups. The distribution of mitochondrial haplotypes suggested that populations from the St. Johns River drainage should be considered their own distinct group (rather than be included in the south—central‐east—northeast Florida group). Although mitochondrial markers failed to detect introgression throughout much of the intergrade zone, nuclear markers revealed an expected decline in introgression from west to east as well as from north to south. Largemouth bass alleles, however, were detected at low frequencies in 12 populations below the southern boundary of the accepted intergrade zone, some of which are the result of stocking. There was no evidence of nonrandom mating or selection against hybrids in the distribution of nuclear genotypes; however, the rarity of largemouth bass mitochondrial haplotypes suggests either assortative mating or reduced fitness in the progeny of female largemouth bass × male Florida bass crosses.

The objectives of this study were to investigate the seasonal changes in pituitary gonadotropins, growth hormone (GH), and estrogen receptor (ER) isoform mRNA in wild female and male largemouth bass (LMB) (Micropterus salmoides) from an unpolluted habitat to better understand reproductive physiology in this ecologically important species. Female pituitary luteinizing hormone (LH) β subunit and follicle-stimulating hormone (FSH) β subunit mRNA showed significant seasonal variation with levels peaking from January to April and were lowest from May through August. Male LMB showed more variation in gonadotropin subunit expression from month to month. Females had approximately 2–3 times higher gonadotropin mRNA levels in the pituitary when compared to males. All three gonadotropin mRNAs in females were positively correlated to gonadosomatic index (GSI), but only LHβ mRNA was correlated to GSI in males. Gonadotropin mRNA expression also increased with increasing oocyte and sperm maturation. Gonadotropin β subunit mRNA expression was positively correlated to GH mRNA in both sexes. The expression of all three ER isoforms was significantly correlated to each other in both sexes. The concurrent increase in all three ER mRNA isoforms with increasing gonadotropin mRNA in females and males suggests a prominent role for E2 feedback on pituitary gonadotropin synthesis in both sexes and that each of the three ER isoforms are likely to play a role in the pituitary during teleost reproduction.

Stocking evaluations for pellet-reared, advanced-fingerling Largemouth Bass Micropterus salmoides often result in low contribution and survival, but little information exists on their survival and behavior soon after release. This study investigated the behavior and mortality of pellet-reared, advanced-fingerling (90-120 mm TL) Florida Bass M. floridanus immediately after they were stocked in Lake Carlton, Florida. A radiotelemetry experiment was conducted to compare initial movement, habitat use, growth, and mortality between stocked hatchery and wild fish. In year 1, we inserted radio transmitters into 50 hatchery fish; in year 2, we tagged 30 hatchery fish and 20 wild fish. All mortality we observed for hatchery fish (from both years) resulted from predation by fish and birds, and most occurred in the first 7 d after tagging. When compared directly with tagged wild fish (n D 20), tagged hatchery fish (n D 30) exhibited greater movement (75 and 124 m/d, respectively), greater proportion of locations offshore (8% and 23%, respectively), slower growth (1.73% and 0.41% of their body weight gained per day, respectively), and higher predation (47% and 0%, respectively). Results of this study suggest that pellet-reared, hatchery Florida Bass suffer more predation than wild bass of similar size initially following their release into the lake. Causes of predation could include less-developed antipredator skills and inefficiency in foraging observed through greater movement, as well as the use of offshore habitat and slower growth. We recommend research that investigates acclimating advanced-fingerling Florida Bass to predators and live prey before release to determine whether initial predation can be reduced after stocking.Supplemental stocking of black bass is a common management strategy in lakes and reservoirs that exhibit limited recruitment. Stocking Largemouth Bass Micropterus salmoides at larger sizes (advanced fingerlings) can improve survival (Buynak and Mitchell 1999;Colvin et al. 2008), and intensively culturing them on pellets in raceways increases the potential for high production (Nelson et al. 1974;Sloane and Lovshin 1995). Artificially spawning Florida Bass M. floridanus 1 out of season (Matthews and Stout 2013) allows biologists to stock fish ahead of native bass in Florida when

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Fish vitellogenin synthesized and released from the liver of oviparous animals is taken up into oocytes by the vitellogenin receptor. This is an essential process in providing nutrient yolk to developing embryos to ensure successful reproduction. Here we disclose the full length vtgr cDNA sequence for largemouth bass (LMB) that reveals greater than 90% sequence homology with other fish vtgr sequences. We classify LMB Vtgr as a member of the low density lipoprotein receptor superfamily based on conserved domains and categorize as the short variant that is devoid of the O-glycan segment. Phylogenetic analysis places LMB Vtgr sequence into a well-supported monophyletic group of fish Vtgr. Real-time PCR showed that the greatest levels of LMB vtgr mRNA expression occurred in previtellogenic ovarian tissues. In addition, we reveal the effects of insulin, 17beta-estradiol (E 2 ), and 11-ketotestosterone (11-KT) in modulation of vtgr, esr, and ar mRNAs in previtellogenic oocytes. Insulin increased vtgr expression levels in follicles ex vivo while exposure to E 2 or 11-KT did not result in modulation of expression. However, both steroids were able to repress insulin-induced vtgr transcript levels. Coexposure with insulin and E 2 or of insulin and 11-KT increased ovarian esr2b and ar mRNA levels, respectively, which suggest a role for these nuclear receptors in insulin-mediated signaling pathways. These data provide the first evidence for the ordered stage-specific expression of LMB vtgr during the normal reproductive process and the hormonal influence of insulin and sex steroids on controlling vtgr transcript levels in ovarian tissues.insulin, oocyte development, steroid hormones, vitellogenin, vitellogenin receptor

Environmental and genetic factors influence fish spawning periodicity (i.e., the distribution of spawning events during the breeding season), but their relative contributions have rarely been evaluated. We evaluated the relative contribution of genetic and environmental effects on spawning periodicity by rearing Florida largemouth bass (FLMB, Micropterus salmoides floridanus) from Lake Okeechobee and intergrade largemouth bass (ILMB, Micropterus salmoides salmoides × M. s. floridanus) from Lake Seminole in a similar environment. Fish from each genetic source population were translocated to experimental ponds at an intermediate latitude in Gainesville, Florida, in September 2003. We used estimated ages of offspring as an index of spawning events to compare spawning distributions between brood sources in ponds and related those results to spawning distributions at source populations for 2004. FLMB began spawning earlier than ILMB in all ponds, and FLMB had a longer spawning season than ILMB. Similarly, FLMB at Lake Okeechobee began spawning earlier and had a longer spawning season than ILMB at Lake Seminole. Environmental factors (e.g., temperature effects) influenced spawning periodicity for both FLMB and ILMB, but spawning periodicity was also influenced by genetic composition in ponds because translocated fish reflected characteristics of their source populations. Thus, both environmental factors and genetic composition influenced spawning periodicity.

Supplemental stocking of fingerling or advanced fingerling Largemouth Bass Micropterus salmoides is a common management strategy for augmenting natural production in low‐recruitment systems. Few studies, however, have evaluated the impact of stocking adult bass taken from donor lakes. Over a period of 6 years, University of Florida researchers stocked Florida Lakes Griffin and Dora with 24,781 wild Florida Bass M. s. floridanus collected by electrofishing from other Florida lakes. During stocking years, stocked fish made up to 10% of the population in Lake Griffin and 27% in Lake Dora from electrofishing samples. However, 1 year after all stocked fish had been released, the proportion of stocked bass had declined to less than 5%, and 3 years after it had declined to less than 1%. We did not detect an increase in recruitment (catch of age‐1 bass) following stocking, so any benefit from stocking was likely short‐lived. We also could not conclude that stocking was responsible for increasing fishing effort because total fishing effort did not increase after stocking. As a result, no additive economic benefits could be attributed to the stocking program. During randomized electrofishing sampling, we collected 51 wild bass that had been released during the stocking program, and genetic analysis determined that two (3.9%) were hybrids and had alleles from nonnative Largemouth Bass. The extrapolation of these results estimated that almost 1,000 hybrids had been introduced into Lakes Griffin and Dora, which were historically identified to contain pure Florida Bass populations. Future wild bass stocking programs should include an appropriate study design for evaluating changes in fish populations, changes in the fishery, and economic consequences of stocking. Furthermore, a risk–benefit assessment should be completed before any stocking program is initiated, including consideration of any potential impacts on biodiversity. Received February 26, 2015; accepted January 6, 2016 Published online May 9, 2016