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Stress of aquatic animals occurs due to physical and physiological disturbances in the aquatic environment or system when transportation, crowding, handling or changes of physical and chemical factors take place. There are three regulatory systems having a vital role in stress response: the neural, endocrine and immune systems. Fish exhibit multiple genomic and physiological responses to adjust the compensatory or adaptive mechanism that allows them to mitigate the stressors, maintain their haemostasis and survive. In this review, we describe multiple important genes that are associated with responses to environmental and husbandry stressors and that could be used as biomarkers of environmental and husbandry stressors in fish. The described environmental and husbandry stressors include salinity, temperature, hypoxia and hyperoxia, confinement, density and handling. The main role of stress response in aquatic animals is to compensate or adapt their biological systems and arrange the metabolism to afford the energy required by the stressor and a wide array of metabolic processes and pathways are involved. We summarized and discussed highly significant genes in several organs and tissues that are involved and active during this adaption process. The traditional stress biomarkers in some circumstances have some difficulties in interpretation of results and lead to tricky diagnosis and searching and understanding alternative tools is critical for aquaculture, fisheries and fish welfare. Using genomic tools to study the candidate genes associated with stress responses are often unique signatures or imprints of specific stressors and could determine early signs of stressors.

In this study, the gonadotropin-releasing hormone (GnRH) genes in spotted halibut were cloned and sequenced by isolating their cDNAs. The species expressed three molecular forms of GnRH in the brain: chicken-type GnRH-II (cGnRH-II), seabream-type GnRH (sbGnRH), and salmon-type GnRH (sGnRH). Phylogenetic analysis divided the molecular forms of GnRHs into three branches: cGnRH-II branch, sGnRH branch, and fish-specific GnRH branch. The spatial expression showed that they had the highest expression levels in the brain. cGnRH-II was exclusively detected in the brain, while sbGnRH had a global expression pattern in all examined organs. sGnRH was detected in the brain, pituitary, and ovary. The temporal changes of brain GnRH mRNA expression levels were examined during ovarian maturation and postspawning, and the serum steroid hormones and gonadosomatic index (GSI) were recorded. Amounts of sbGnRH mRNA substantially elevated (P < 0.05) during ovarian maturation, which concomitant with considerable elevation of GSI and serum steroids levels. On the contrary, neither sGnRH nor cGnRH-II mRNA levels showed significant changes during ovarian maturation in this study. These results suggested that these three GnRH genes are the important regulators for the differential expression of GnRH in spotted halibut, and would help us better understand the reproductive endocrine mechanism of spotted halibut.

Concerns over the economic feasibility of commercial aquaculture production of bluegills Lepomis macrochirus have heightened the need for strategies to enhance growth. Recent studies have shown that individually reared bluegill males can grow twice as fast as females; such studies have generated increased interest in development of mostly male or all-male populations. In this study, we developed a practical procedure to establish mostly male bluegill groups through grading selection and we tested their growth against that of a normal population. A single cohort of bluegill juveniles was cultured in a pond for 1 year; when the fish reached a mean weight of 30.1 g, the cohort was graded and divided into two mostly male groups (top 25% and top 50% of fish by total length) and a mixed-sex control group. The percentage of males in each group was as follows: 50.0% in the mixed control group, 75.4% in the top 25% group, and 69.7% in the top 50% group. Weight gain per fish in the top 25% group was signif...

A total of 45 microsatellite loci from yellow perch, Perca flavescens, were isolated and characterized. Among the 45 microsatellite loci, 32 had more than two alleles. A wild population of P. flavescens (n = 48) was used to examine the allele range of the microsatellite loci. Mendelian inheritance of alleles was confirmed by examining the amplified products in pair-mated families. The number of alleles for the 32 polymorphic loci varied from two to 16, and observed heterozygosity ranged between 0.024 (YP79) and 0.979 (YP60). Cross-species polymorphic amplification in four other Percidae species was successful for 22 loci.

— An indicated demand for sunfish (Lepomis spp.) as a food fish remains untested because of continuing inability to efficiently rear these fishes to required large sizes (≥227 g; 0.5 lbs). A recent study involving parallel, indoor rearing of two sunfishes under favorable conditions showed that bluegills Lepomis macrochirus possessed markedly higher growth capacity than B × G hybrids (F1: male bluegill × female green sunfish, Lepomis cyanellus). B × G hybrids had been thought to possess superior growth capacity and so have received more attention than bluegills as a food-fish candidate in many areas of the USA. Reanalysis of data from the recent study with emphasis on gender differences revealed that the male bluegills possessed much higher growth capacity than male B × G hybrids, at least from May to March as Age 1 and then early Age 2 fish. Male bluegills reached 67% of food-market weight within the 10-mo period from a starting weight of 7 g; male B × G hybrids reached only 24% of this weight. Male bluegills’ more rapid growth versus male B × G hybrids’ apparently involved less growth energy allocation to gonad development. Female bluegills grew slower than male bluegills but also outgrew male and female B × G hybrids whose growth trajectories declined in midsummer (June) and remained largely flat through March. The previous view that B × G hybrids possess higher growth capacity than bluegills was fostered by studies in ponds where bluegill growth can be impeded by high reproduction rates and, as this study reveals, by high densities and exposure to suboptimal temperatures when their growth potential is high. Indoor rearing of male bluegills should ameliorate most pond-related growth impediments and take fuller advantage of their rapid growth capacity.

The culture of yellow perch Perca flavescens has received considerable interest in the Midwest and elsewhere in the USA as a result of the decline of wild populations and their high market demand. In this study, the effects of size-grading on the production efficiency and growth performance of food-sized yellow perch were determined in six 0.1-ha ponds by grading fingerlings into three size-groups (mean initial size): small (5.3 g), large (18.3 g), and unsorted (11.3 g). The mean percentage of marketable production from large-group ponds was significantly greater than that from the small- and ungraded-group ponds. The final biomass of large size-groups was 77% and 27% greater than that of small and ungraded groups, respectively, although no significant differences in total production were detected among the three size-groups. Size-sorting of fingerling yellow perch did not result in improved growth of the small-fish group. No significant differences in growth rates among the three groups were det...

OBJECTIVE: S-mephenytoin hydroxylase is a polymorphic cytochrome P450 (CYP) enzyme that catalyzes the metabolism of omeprazole, a proton-pump inhibitor, and some other drugs. The aim of this survey was to investigate the distribution of the genotype of S-mephenytoin hydroxylase in Chinese people. METHODS: One hundred and fifty-five unrelated healthy volunteers were selected and their blood samples were used for genotyping by PCR-restriction enzyme analysis. DNA from homozygous extensive metabolizers (EM) could be digested into two fragments, whereas poor metabolizers (PM) could not be digested and heterozygous EM could be partly digested. RESULTS: Two mutations of CYP2C19 were found; that is, m1 and m2. The frequency of the PM (m/m) genotype was 15.5% (24/155) and that of EM was 84.5% (131/155). The EM included 36.8% (57/155) homo-EM (wt/wt) and 47.7% (74/155) hetero-EM (wt/m). CONCLUSIONS: There were two forms of CYP2C19 mutations. The frequency of PM (m/m) and heterozygous EM genotype (w/m) in Chinese people were significantly higher than those of Western white people. Hetero-EM were more common than homo-EM in the Chinese population. The genotyping variation might explain the different effect of PPI on individuals.

Reeves shad Tenualosa reevesii is one of China's best known anadromous fish, but is presently on the verge of extinction. There is an urgent need for conservation of this species through artificial reproduction and culture. In this study, shad broodstock were held in captivity then were induced to spawn with serial injections of luteinizing hormone-releasing hormone analogue (LHRHa) following GtH priming by implantations of 17-methytestosterone (T) combined with environmental manipulations. Induced maturation of 4, 5, and 6-year-old females reached 83.3%, 87.5%, and 100%, respectively, while fish in control treatments remained immature. During the gonadal development priming period, mean serum 17-estradiol levels in the T treatment were significantly higher than the LHRHa treatment and control fish. Gonadal development of females was suppressed when their mesenteric fat index was below 1.5% by April. The effective accumulating temperatures for female and male maturation were 3,995 ± 31.4 C/d and 2,278 ± 8.9 C/d, respectively. Two injections of LHRHa in combination with domperidone (DOM) and environmental regulations were effective in inducing ovulation. About 800,000 fertilized ova were obtained (fertilization 75%) in 1995, and 5,000 fry were hatched in 1996. These results are an important step to develop shad culture and save this endangered species.

Maximum handling sizes, prey size and species preferences, and ad libitum consumption rates were determined for three size classes of redear sunfish Lepomis microlophus feeding on Physa gyrina and Helisoma trivolvis, two common aquaculture-pond snails which serve as intermediate hosts for fish parasites. Maximum handling-size experiments indicated that redear sunfish as small as 14-cm total length were capable of consuming all sizes of Physa typically observed in ponds, whereas only redear sunfish of at least 32-cm total length are capable of consuming all commonly observed sizes of pond-dwelling Helisoma. When presented with a range of sizes of both snail species, redear sunfish consumed higher proportions of smaller- and medium-sized snails; the largest snails offered were uneaten or consumed in relatively small quantities. Multiple linear regression was applied to consumption data to develop a simple model for predicting mean daily ad libitum consumption rate (g/g per d) for redear sunfish feeding on snails with temperature (20–27 C) and fish total length (9–24 cm) as independent variables. Our findings will facilitate prediction of numbers of redear sunfish of a given size required to control populations of Physa and Helisoma in ponds. Such predictions will enable pond owners to quickly evaluate whether stocking redear sunfish as a control agent for undesirable snail populations will be economically and logistically feasible. Findings also indicate potential limitations in the use of redear sunfish to control populations of Helisoma due to the inability of redear sunfish as large as 24-cm total length to consume the largest 30–40% of Helisoma commonly observed in ponds and to the expense of stocking larger fish (32-cm total length) capable of consuming all sizes of Helisoma.

There is interest in knowing whether the bluegill Lepomis macrochirus or a hybrid of bluegill and green sunfish L. cyanellus (F1: male bluegill × female green sunfish; hereafter called B × G hybrids) can be grown faster to food market size (225–340 g). The predominant view is that the hybrid grows faster. In this study, the inherent growth capacities (IGCs) of age-1 bluegills and B × G hybrids were determined over four successive 25-d periods (May–August 2000) by holding them individually at 22°C and feeding them to apparent satiation three times daily. The hybrid's IGC was greater during period 1 but fell to only 33% of the bluegill's over the three subsequent periods; the consumption and gross growth efficiency (GGE) of the hybrid showed similar declining patterns. The growth-in-weight trajectory of bluegills crossed above that of the hybrids at about 30 g. Gonadosomatic index values suggested that hybrid growth rates declined below those of the bluegill because the former invested more energy ...