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The impact of nonconsumptive effects (NCEs) in structuring predator-prey interactions and trophic cascades is a prominent area of ecological research. For NCEs to occur, prey need to be able to detect the presence of predators through sensory mechanisms. The investigation of the role of different sensory modalities in predator detection has lagged behind the development of NCE-based theories. This study aimed to determine whether a hierarchy in the reliance upon sensory modalities exists in the rusty crayfish ( Orconectes rusticus (Girard, 1852) = Faxonius rusticus (Girard, 1852)) for predator detection and if this hierarchy is altered across different sensory environments (flowing and nonflowing environments). Rusty crayfish were exposed to largemouth bass ( Micropterus salmoides (Lacépède, 1802)) odor in either a flowing or nonflowing arena where behavior was recorded under different sensory lesions. Linear mixed models were conducted to determine the impact of lesions, flowing environments, and the interactive effects of lesions and flowing environments on the rusty crayfish ability to respond to predatory stimuli. Results from this study support the significance of sensory multimodality in the rusty crayfish for accurately detecting and assessing predatory threats. Results from this study also suggest a hierarchy in the reliance upon sensory modalities in the rusty crayfish that is dependent upon the environment and the location of rusty crayfish within an environment. [ABSTRACT FROM AUTHOR]

Abstract: We examined evidence for density‐dependent growth of Largemouth Bass Micropterus salmoides in the recruited life stage (age 2 and older) at eight large (>4,000 ha) Alabama reservoirs from standardized electrofishing survey data. Using mean length at age as a measure of cumulative growth and electrofishing catch rates as the basis for a cumulative index of density, we found weak support for the hypothesis that mean length at age was inversely related to Largemouth Bass density. The mean length at age of age‐5 Largemouth Bass was positively related to the cumulative density index, which is inconsistent with the prediction of an inverse association under compensatory density dependence. Moreover, the strength of the effect was weak, with a 9‐mm increase in mean length at age per 100% increase in the density index. No other age‐classes (ages 2 through 6 were examined) exhibited density‐dependent mean length at age. Similarly, relative weight was unrelated to the density index. Analyses of changes in mean length at age, relative weight, and the density index over time indicate that each of these variables have increased slightly since the mid‐1990s for some age‐classes. Our analysis of Largemouth Bass mean length at age at these reservoirs suggests that strong density‐dependent growth responses are unlikely in the recruited life stage at these large reservoir systems. If this is the case, implementing minimum length limits at these reservoirs is likely to avoid unintended negative consequences for Largemouth Bass growth and size structure. [ABSTRACT FROM AUTHOR]

To investigate the effects of brewer's yeast hydrolysate (BYH) on the growth and intestinal bacteria diversity of largemouth bass ( Micropterus salmoides )sthe fish were fed with basal diet supplemented with or without BYH (0, 0.1%, 0.2%) for 8 weeks. The results showed that the weight gain rate, survival rate, hepatosomatic index, organ coefficient and condition factor were not significantly different among the groups, except intraperitoneal fat ratio was significantly reduced in 0.2% BYH group. Totally 25 phyla, 56 classes, 103 orders, 155 families, 216 genera and 1051 operational taxonomic units (OTUs) of bacteria were identified from the 2,057,871 sequences obtained by Illumina MiSeq 16S rRNA sequencing. Among them, Fusobacteria, Firmicutes and Proteobacteria were the most three dominant phyla in the intestines regardless of diets. Furthermore, the richness of Fusobacteria, Cyanobacteria, Tenericutes and Actinobacteria in 0.2% BYH group was significantly lower than those of the control group. Interestingly, the ratio of Bacteroides/Firmicutes was decreased in the groups fed with BYH, this might be related to the modulations of energy absorption and storage, resulting in the decrease of fat deposition in fish body. At the genus level, several bacterial genera ( Plesiomonas , Mycoplasmas , Synechococcus and Peptostreptococcus ) which were potential pathogens of fish were significantly decreased in the groups fed with BYH. By contrast, a significant increase of Cetobacterium which could ferment peptides and carbohydrates to produce vitamin B 12 was observed in fish fed with BYH, indicating that dietary BYH was helpful in propagation of some probiotic bacteria. Taken together, the overall intestinal bacterial diversity was decreased in fish fed with BYH which might promote the growth of some probiotics and inhibit some pathogenic bacteria, suggesting that BYH may serve as feed additive in modulation of the gut bacterial community of largemouth bass to decrease the potential pathogens. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work was to determine whether juvenile and adult European seabass (Dicentrarchus labrax L.), fed ad libitum manually and with self‐feeding demand feeders, respectively, were able to discriminate between a fish oil‐based diet and a series of diets made with vegetable oils (soybean, linseed, rapeseed and sunflower oil), as well as a fat‐free diet. Adult D. labrax (443.6 ± 108.8 g) selected diets made from soybean (SYO) and rapeseed (RO) in proportions similar to fish oil (FO). Demand levels for the other two diets, sunflower (SUO) and linseed (LO) oils, were significantly lower than FO, whilst juveniles (56.4 ± 11.2 g) displayed a preference for SYO and FO. The lowest demand levels were associated with a fat‐free diet (FF). Selection percentages of the diets for adult and juvenile fish were, respectively, FF—22.96% and 39.76%, SYO—43.02% and 53.26%, LO—36.48% and 36.19%, SUO—39.87% and 37.32%, and RO—46.38% and 40.94%. The animals’ size and feeding method did not significantly affect dietary selection. However, a statistical difference in specific growth rate (1.37% ± 0.26% day−1) for juveniles was only observed for FO+FF combination. For juveniles, no differences were observed in the conversion index. The juvenile group (FO + FF) had the highest food intake (2.00 ± 0.35 g 100 g−1 body weight). Moreover, the groups fed FO + SUO and FO + RO consumed the least. In conclusion, this study shows D. labrax can discriminate between diets where the only difference is the lipid source. These findings should be used to understand the acceptance or rejection of different source oils, which are increasingly being used in aquaculture such as aquafeeds for European seabass. [ABSTRACT FROM AUTHOR]

Hatchery-reared fingerling Guadalupe BassMicropterus treculiiare stocked into central Texas rivers to restore threatened populations and combat hybridization with Smallmouth BassM. dolomieu. Fry survival in hatchery rearing ponds has declined by more than 50% in recent years, and pilot investigations indicated that exposure to high dissolved oxygen (DO) concentrations (>20 mg/L; hyperoxia) during tempering might have contributed to fry mortality. To test this hypothesis, Guadalupe Bass swim-up fry (11 d posthatch; 8.45 ± 0.25 mm TL [mean ± SD]) were exposed to normbaric DO concentrations ranging from 7.9 to 33.3 mg/L at 18°C, mimicking the hatchery tempering protocols followed during 2014 and 2015. After a 30-min exposure to the DO treatment (flow rate = 18 L/h), jars were flushed with nonoxygenated water for 1 min to rapidly lower the DO, mimicking the release of fry into ponds after tempering. Jars were then supplied with freshwater at a rate of 36 L/h and were monitored for 72 h. One control (A) was subjected to the same protocol but without oxygen supplementation; the other control (B) was not subjected to the 30-min exposure or flushing. Dead fry among treatments were recorded and removed every 24 h. Mortalities were observed within 6 h. Surviving fry were counted and measured after 72 h. Fry survival at 72 h was negatively correlated with increasing DO concentrations (Pearson’s product-moment correlation coefficient = –0.79) and declined significantly above 20 mg/L. Fry populations exposed to the highest oxygen concentration visually appeared more lethargic than fry in other treatments. The results of our study suggest that hyperoxia contributed to the low survival of fry in recent years. We recommend DO concentrations below 15 mg/L and avoiding DO levels above 20 mg/L (212% saturation at 18°C) when transporting and tempering Guadalupe Bass fry. We also recommend verifying the oxygen limits of other black bassMicropterusspp. Received April 26, 2017; accepted June 2, 2017Published online August 2, 2017 [ABSTRACT FROM AUTHOR]

Nisin, a natural substance from Lactococcus lactis, displays a promising antibacterial ability against the gram-positive bacteria. However, it is susceptible to the external environment, i.e. temperature, pH, and food composition. In this study, a dual stabilization method, coaxial electrospinning, was applied to protect nisin in food packaging materials and the effect of nisin concentration on the properties of the nanofibers was investigated. The core-shell nanofibers with pullulan as a core layer and carboxymethyl chitosan (CMCS)/polyethylene oxide (PEO) as shell layer were prepared, and then the prepared CMCS-nisin nanogels (CNNGs) using a self-assembly method were loaded into the core layer of the nanofibers as antibacterial agents. The result revealed that the smooth surface can be observed on the nanofibers by microstructure characterization. The CNNGs-loaded nanofibers exhibited enhanced thermal stability and mechanical strength, as well as excellent antibacterial activity. Importantly, the as-formed nanofibers were applied to preserve bass fish and found that the shelf life of bass fish packed by CNNGSs with nisin at a concentration of 8 mg/mL was effectively extended from 9 days to 15 days. Taken together, the CNNGs can be well stabilized with the core-shell nanofibers, thus exerting significantly improved antimicrobial stability and bioactivity. This special structure exerts a great potential for application as food packaging materials to preserve aquatic products. • The CNNGs as antibacterial agents were prepared by a self-assembly method. • The CNNGs-loaded core-shell nanofibers were fabricated by coaxial electrospinning. • The antibacterial activity of the nanofibers extremely relied on the nisin content. • The optimized PCCP-8 could extend the shelf life of bass fish by almost double. [ABSTRACT FROM AUTHOR]

The small geographic range and narrow habitat niche inhabited by this species in the heavily populated central Florida region suggests that habitat loss and contamination are potential threats to the Lake Eustis Pupfish. Lack of exotic aquatic vegetation management, alteration of lake shore habitat, and introduction of nonnative, predatory fish are other threats that may cause population declines. The Lake Eustis Pupfish I Cyprinodon variegatus hubbsi i is a small fish that can reach up to 3 in (7.6 cm) in total body length. [Extracted from the article]

PCBs and OCPs were analyzed in fish (bass) taken along Chinese coastal fisheries. In the bass muscle, PCB, DDT and HCH concentrations were in the range of 1.02–2.2 ng/g, 0.44–1.74 and 2.84–106.11 ng/g ww, respectively. Spatial distribution showed that the concentrations of target contaminants in bass from south fisheries were in general much lower than those from north fisheries in China. The ratios of OCP congeners suggested that technical DDT was not the main input and a recent usage of lindane or old technical HCH residuals could be the source of HCHs. The OCC concentrations in liver (127–442.43 ng/g ww) from selected samples were 8–12 and 10–14 times higher than those in gills and muscles, respectively. Based on the maximum allowable fish assumption rate ( CR lim and CR mm ), it could cause human health risk, by consuming bass samples taken from highly contaminated fisheries including QD and ST. [ABSTRACT FROM AUTHOR]

The Guadalupe Bass, Micropterus treculii is endemic to the Hill Country region of central Texas, US, and its entire native distribution is within Texas, including portions of the Brazos, Colorado, Guadalupe, and San Antonio River basins. Currently, the genetic integrity of Guadalupe Bass populations are threatened by hybridization with introduced, nonnative Smallmouth Bass, M. dolomieu. Species-isolating mechanisms (or lack thereof) are not well understood for these two species. To identify potential mechanisms influencing hybridization in Guadalupe Bass populations, our objectives were to characterize: (1) spawning season and duration, (2) nesting habitat, (3) courtship behaviors (including color pattern changes), and (4) parental care pattern. The reproductive ecology (spawning season, nest sites) and behavior (courtship, parental care) of Guadalupe Bass were found to be similar to what has been reported in Smallmouth Bass, possibly contributing to continued potential for hybridization. Guadalupe and Smallmouth Bass share 12 reproductive behaviors and similar color patterns during courting and spawning interactions. This study is the first to report an individual male Guadalupe Bass simultaneously courting and spawning with two to four females in one nest, suggesting the need for further investigation of links between hybridization potential, sex ratio and population structure in Guadalupe Bass. We recommend investigation of female mate choice and sexual competition comparing Guadalupe Bass and Smallmouth Bass. Additionally, future conservation efforts should focus on nesting habitat in existing pure strain Guadalupe Bass populations. [ABSTRACT FROM AUTHOR]

The activity of muscle glycolytic enzymes scales positively with body size in active fish, a phenomenon thought to counter the increased costs of burst swimming faced by larger individuals. Recent work argued that changes in these enzymes during ontogeny additionally reflect changes in foraging ecology. Here, we evaluated the relationship between muscle anaerobic metabolism and foraging ecology in a population of wild smallmouth bass ( Micropterus dolomieu) by relating activity of muscle lactate dehydrogenase (LDH) to estimates of trophic position and habitat use obtained from stable isotope signatures. As expected, LDH activity increased with body size. However, further analysis showed associations between foraging ecology and LDH activity. Specifically, a shift to higher trophic position, indicating a change in diet, was paralleled by a shift to increased LDH activity. However, a steady mass-specific decrease in LDH activity was observed as the fish grew above the size associated with this diet shift. Further, lower LDH activity was associated with increasing use of littoral carbon sources. These findings contribute to our understanding of how plasticity in muscle anaerobic potential is associated with fish foraging ecology. [ABSTRACT FROM AUTHOR]

Three experiments assessed the effects of cold-shock induced triploidy on (1) the incidence of abnormal cell cleavage during embryogenesis, (2) hatching success and the proportion of live yolk-sac larvae in normally cleaved versus abnormally cleaved embryos, and (3) survival of triploid larvae of spotted sand bass (Paralabrax maculatofasciatus). All spawns were obtained by hormonal induction (LHRHa). Triploidy was induced by cold shock shortly after fertilization. In experiment 1, the percentage of abnormal cell cleavage was significantly higher (P < 0.05) in the cold-shocked group than in the control group, while the hatching rate and the proportion of live yolk-sac larvae were significantly lower (P < 0.05). In experiment 2, when normally and abnormally cleaved embryos from the control and cold-shocked groups were incubated separately, normal cleaved embryos in the cold-shocked group showed a significantly higher hatching rate and proportion of live yolk-sac larvae than abnormally cleaved embryos in the same group. No difference was observed in the control group. In experiment 3, a significant decrease (P < 0.05) in the triploidy count was observed throughout the larval period. Final survival was drastically lower for triploid larvae compared to cold-shocked diploids and untreated eggs. Low triploidy percentages at the end of the larval period would seriously hinder the development of triploid sand bass culture. Three experiments assessed the effects of cold-shock induced triploidy on (1) the incidence of abnormal cell cleavage during embryogenesis, (2) hatching success and the proportion of live yolk-sac larvae in normally cleaved versus abnormally cleaved embryos, and (3) survival of triploid larvae of spotted sand bass (Paralabrax maculatofasciatus). All spawns were obtained by hormonal induction (LHRHa). Triploidy was induced by cold shock shortly after fertilization. In experiment 1, the percentage of abnormal cell cleavage was significantly higher (P < 0.05) in the cold-shocked group than in the control group, while the hatching rate and the proportion of live yolk-sac larvae were significantly lower (P < 0.05). In experiment 2, when normally and abnormally cleaved embryos from the control and cold-shocked groups were incubated separately, normal cleaved embryos in the cold-shocked group showed a significantly higher hatching rate and proportion of live yolk-sac larvae than abnormally cleaved embryos in the same group. No difference was observed in the control group. In experiment 3, a significant decrease (P < 0.05) in the triploidy count was observed throughout the larval period. Final survival was drastically lower for triploid larvae compared to cold-shocked diploids and untreated eggs. Low triploidy percentages at the end of the larval period would seriously hinder the development of triploid sand bass culture. [ABSTRACT FROM AUTHOR]

Striped bass ( Morone saxatilis ), white bass ( Morone chrysops ), and their hybrid are an important group of fish prized for recreational angling in the United States, and there and abroad as a high-value farmed fish. Regardless of habitat, it is not uncommon for fish of the genus Morone to encounter and cope with conditions of scarce oxygen availability. Previously, we determined that hybrid striped bass reared under conditions of chronic hypoxia exhibited reduced feed intake, lower lipid and nutrient retention, and poor growth. To better understand the molecular mechanisms governing these phenotypes, in the present study, we examined the transcriptomic profiles of hepatic tissue in hybrid striped bass exposed to chronic hypoxia (90 days at 25% oxygen saturation) and acute hypoxia (6 h at 25% oxygen saturation). Using high-throughput RNA-seq, we found that over 1400 genes were differentially expressed under disparate oxygen conditions, with the vast majority of transcriptional changes occurring in the acute hypoxia treatment. Gene pathway and bioenergetics analyses revealed hypoxia-mediated perturbation of genes and gene networks related to lipid metabolism, cell death, and changes in hepatic mitochondrial content and cellular respiration. This study offers a more comprehensive view of the temporal and tissue-specific transcriptional changes that occur during hypoxia, and reveals new and shared mechanisms of hypoxia tolerance in teleosts. [ABSTRACT FROM AUTHOR]

The genus Edwardsiella is composed of a diverse group of facultative anaerobic, gram-negative bacteria that can produce disease in a wide variety of hosts, including birds, reptiles, mammals, and fish. Our report describes the isolation and identification of Edwardsiella piscicida associated with chronic mortality events in 2 separate captive largemouth bass (Micropterus salmoides) populations in New York and Florida. Wet-mount biopsies of skin mucus, gill, kidney, and spleen from several affected largemouth bass contained significant numbers of motile bacteria. Histologic examination revealed multifocal areas of necrosis scattered throughout the heart, liver, anterior kidney, posterior kidney, and spleen. Many of the necrotic foci were encapsulated or replaced by discrete granulomas and associated with colonies of gram-negative bacteria. Initial phenotypic and matrix-assisted laser desorption ionization–time of flight mass spectrometric analysis against existing spectral databases of recovered isolates identified these bacteria as Edwardsiella tarda. Subsequent molecular analysis using repetitive sequence mediated and species-specific PCR, as well as 16S rRNA, rpoB, and gyrB sequences, classified these isolates as E. piscicida. As a newly designated taxon, E. piscicida should be considered as a differential for multiorgan necrosis and granulomas in largemouth bass. [ABSTRACT FROM AUTHOR]

Leptin is an anorexigenic peptide hormone that circulates as an indicator of adiposity in mammals, and functions to maintain energy homeostasis by balancing feeding and energy expenditure. In fish, leptin tends to be predominantly expressed in the liver, another important energy storing tissue, rather than in fat depots as it is in mammals. The liver also produces the majority of circulating insulin-like growth factors (IGFs), which comprise the mitogenic component of the growth hormone (GH)-IGF endocrine growth axis. Based on similar regulatory patterns of leptin and IGFs that we have documented in previous studies on hybrid striped bass (HSB: Morone saxatilis × Morone chrysops ), and considering the co-localization of these peptides in the liver, we hypothesized that leptin might regulate the endocrine growth axis in a manner that helps coordinate somatic growth with energy availability. Using a HSB hepatocyte culture system to simulate autocrine or paracrine exposure that might occur within the liver, this study examines the potential for leptin to modulate metabolism and growth through regulation of IGF gene expression directly, or indirectly through the regulation of GH receptors (GHR), which mediate GH-induced IGF expression. First, we verified that GH (50 nM) has a classical stimulatory effect on IGF-1 and additionally show it stimulates IGF-2 transcription in hepatocytes. Leptin (5 and/or 50 nM) directly stimulated in vitro GHR2 gene expression within 8 h of exposure, and both GHR1 and GHR2 as well as IGF-1 and IGF-2 gene expression after 24 h. Cells were then co-incubated with submaximal concentrations of leptin and GH (25 nM each) to test if they had a synergistic effect on IGF gene expression, possibly through increased GH sensitivity following GHR upregulation by leptin. In combination, however, the treatments only had an additive effect on stimulating IGF-1 mRNA despite their capacity to increase GHR mRNA abundance. This suggests that leptin’s stimulatory effect on GHRs may be limited to enhancing transcription or mRNA stability rather than inducing full translation of functional receptors, at least within a 24-h time frame. Finally, leptin was injected IP (100 ng/g and 1 μg/g BW) to test the in vivo regulation of hepatic IGF-1 and GHR1 gene expression. The 100 ng/g BW leptin dose significantly upregulated in vivo IGF-1 mRNA levels relative to controls after 24 h of fasting, but neither dosage was effective at regulating GHR1 gene expression. These studies suggest that stimulation of growth axis component transcripts by leptin may be an important mechanism for coordinating somatic growth with nutritional state in these and perhaps other fish or vertebrates, and represent the first evidence of leptin regulating GHRs in vertebrates. [ABSTRACT FROM AUTHOR]

The Neotropics harbor the world's most diverse freshwater fish fauna, with many of these species supporting major commercial, subsistence, or sport fisheries. Knowledge of population genetic structure is available for very few Neotropical fishes, thereby restricting management. To address this need, we examined population genetic variation in mtDNA control region sequences and twelve microsatellite loci in the speckled or barred peacock bass, Cichla temensis. Moderate and statistically significant genetic divergence among localities indicates that migration is low in this species, implying that populations inhabiting tributaries or even smaller spatial units should constitute management units. Analysis of molecular variance of mtDNA sequences identified six areas with largely exclusive haplotype clades, and a seventh area of high admixture, but major drainage basins harbored non-monophyletic haplotype groups. On the other hand, molecular variation in the microsatellite data was best explained by drainage basin and, subsequently, by the seven areas. Populations in these seven areas could be considered evolutionarily significant units (ESUs), and, therefore, we tested hypotheses explaining the discordant signal of mtDNA and microsatellite data using approximate Bayesian computation. This analysis indicated that the divergence of mtDNA clades preceded the divergence of contemporary ESUs across basins, with subsequent lineage sorting among ESUs due to reduced gene flow. Available genetic and ecological information indicates that C. temensis populations of major tributary rivers should be managed as separate stocks that likely are adapted to local environmental conditions. [ABSTRACT FROM AUTHOR]

A survey of largemouth ( Micropterus salmoides) and smallmouth bass ( Micropterus dolomieu) parasite communities in Oneida Lake, New York, was conducted in the summer of 2012 and compared to an earlier survey conducted by Van Cleave and Mueller during the summers of 1929 to 1931. The component helminth communities between surveys were 31% similar in composition for largemouth and 28% similar for smallmouth bass. Between species, the component helminth communities were considerably more similar in the present survey (71%) than in the survey conducted by Van Cleave and Mueller (47%). Seven species reported by Van Cleave and Mueller were present in this survey and 21 species are new records for the bass of Oneida Lake. Van Cleave and Mueller did not report prevalence values for several taxa (Monogenea, Copepoda, Myxozoa, and a Trichodina sp.) that were important for separation of parasite infracommunities in species space for both bass species. These parasites represented 28% of all species found in the current survey and may be ecologically important. Several species of parasites exhibited differences in prevalence between surveys. Two species ( Rhipidocotyle papillosa and Crepidostomum cornutum) were absent from this survey but were reported as common in the 1929-1931 survey and almost certainly represent extirpations that coincide with the loss of their native bivalve hosts from Oneida Lake. Other differences in the parasite communities may also be explained by the ecological disturbances in Oneida Lake over the past 81 yr. The changes in bass parasite communities between surveys emphasize the importance of recognizing the historical nature of parasite communities, especially in ecosystems with a history of large-scale changes. Most importantly our findings suggest that, similar to trends observed in free-living freshwater biotic communities, anthropogenic ecosystem disturbances may homogenize fish parasite communities. [ABSTRACT FROM AUTHOR]

Since its first description by Gilbert and Cramer (1897) (originally as Melanostoma argyreum), Synagrops argyreus was considered to be endemic to Hawaii. New data from the southern Indian Ocean in the Madagascar Channel and the Coral and Tasman Seas reveal a considerable wider geographical distribution of the species, adding to the growing number of pseudoceanic species with a wide distribution pattern in the Indo- Pacific. [ABSTRACT FROM AUTHOR]

Pituitary adenylate cyclase activating polypeptide (PACAP) has a wide range of biological functions. We cloned the full-length cDNAs encoding PACAP and PACAP-related peptide (PRP) from the brain of largemouth bass ( Micropterus salmoides) and used real-time quantitative PCR to detect PRP-PACAP mRNA expression. The PRP-PACAP cDNA has two variants expressed via alternative splicing: a long form, which encodes both PRP and PACAP, and a short form, which encodes only PACAP. Sequence analysis results are consistent with a higher conservation of PACAP than PRP peptide sequences. The expression of PACAP-long and PACAP-short transcripts was highest in the forebrain, followed by the medulla, midbrain, pituitary, stomach, cerebellum, intestine, and kidney; however, these transcripts were either absent or were weakly expressed in the muscle, spleen, gill, heart, fatty tissue, and liver. The level of PACAP-short transcript expression was significantly higher than expression of the long transcript in the forebrain, cerebella, pituitary and intestine, but lower than that of the long transcript in the stomach. PACAP-long and PACAP-short transcripts were first detected at the blastula stage of embryogenesis, and the level of expression increased markedly between the muscular contraction stage and 3 d post hatch (dph). The expression of PACAP-long and PACAP-short transcripts decreased significantly in the brain following 4 d fasting compared with the control diet group. The down-regulation effect was enhanced as fasting continued. Conversely, expression levels increased significantly after 3 d of re-feeding. Our results suggest that PRP-PACAP acts as an important factor in appetite regulation in largemouth bass. [ABSTRACT FROM AUTHOR]