注射LHRH-A2对刀鲚的催产效果及其雌鱼血液生化指标的影响

为了丰富刀鲚人工繁殖理论,探明LHRH-A2对刀鲚的催产效果及其雌鱼血液生化指标的影响,本研究以2冬龄人工养殖刀鲚为研究对象,通过注射LHRH-A2进行人工催产,并分析催产效果;同时应用放射性免疫、化学发光等方法,对人工催产过程中刀鲚雌鱼的血液生化指标进行了系统研究。结果显示,按照雌鱼30μg/kg、雄鱼减半的剂量注射LHRH-A2,刀鲚亲鱼死亡率为16.67%±3.34%;存活刀鲚亲鱼群体中,效应时间为21~24 h,催产率为83.33%±3.34%,受精率为75.06%±6.19%。注射催产素21 h内,血浆中17β-雌二醇(17β-estradiol,E2)、催乳素(prolactin)、甲状腺素(thyroxine,T4)、皮质醇(cortisol)、总蛋白(total protein,TP)、乳酸(lactate)在人工催产过程中表现出先上升后下降的规律;三碘甲腺原氨酸(three iodine thyroid,T3)、甘油三酯(triglyceride,TG)、Cl–呈现持续下降趋势;谷丙转氨酶(alanine transaminase,ALT)、谷草转氨酶(aspartate transaminase,AST)、渗透压(osmotic pressure)、K+、Na+呈现持续上升的趋势。比较以上血浆指标在产卵组和未产卵组的实验结果,产卵组形成高皮质醇、TP、TG、渗透压、Na+、K+的血浆环境和低E2、催乳素、乳酸、T4、T3、Cl-、ALT、AST的血浆环境,而未产卵组的这些指标与产卵组相反。结果表明,人工催产过程对肝脏、肾脏等正常功能造成了影响,从而抑制催产素LHRH-A2对卵子的正向调控作用。本研究初步揭示了人工催产应激对刀鲚雌鱼成功排卵的影响机制,为进一步优化刀鲚的规模化人工繁殖提供科学依据。     

Efficacy of 17 α‐methyl testosterone and letrozole on sex reversal of protogynous grouper,Epinephelus tauvina (Forskal, 1775) and spawning performance of sex‐reversed males

This study aimed to test the efficacy of 17 α‐methyl testosterone (17 α‐MT) alone and in combination with letrozole, an aromatase inhibitor, for the induction of sex reversal in protogynous greasy grouper, Epinephelus tauvina. Further, the long‐lasting effects of these treatments and spawning performance of sex‐reversed males were also investigated. Greasy grouper with oocytes in the perinucleolus stage were implanted with 5 mg 17 α‐MT kg^?1 body weight (T₁), 5 mg 17 α‐MT and 0.2 mg letrozole kg^?1 body weight (T₂) and 5 mg 17 α‐MT with 0.4 mg letrozole kg^?1 body weight (T₃) and no androgens/enzyme inhibitor implanted (C). The 17 α‐MT alone and in combination of letrozole‐induced sex reversal in greasy grouper, whereas untreated control fish (C) showed normal ovarian development. However, T₂ and T₃ group showed 100% sex reversal and completion of spermatogenesis up to functional male phase in 2 and 3 months, respectively, whereas T₁ group resulted in only 66.67% functional male with motile spermatozoa after 4 months. Sex‐reversed males successfully fertilized the eggs during induced spawning. There were significant differences on fertilization and hatching rates between T₂ group (79.00 ± 4.36%; 77.67 ± 2.87%, respectively) and T₁ group (57.67 ± 3.17%; 63.87 ± 2.91%, respectively). The result suggested that 17 α‐MT (5.0 mg kg^?1 BW) in combination with letrozole (0.2 mg kg^?1 BW) has the potential to produce 100% sex‐reversed male in short period in greasy grouper, which might greatly help in seed production of greasy grouper.     

Implications of using small meshed gillnets for the sustainability of fish populations: a theoretical exploration based on three case studies

The study explores the impacts of varying gillnet mesh size and fishing level on yield per recruit (Y/R), escapement spawning stock (ESS) and mega‐spawners (MS) of three widely distributed freshwater fishery target species. Y/R is maximised when the optimal length of capture (L_cap) is above the size of maturity (L₅₀). However, the unimodal shape of gillnet selectivity results in lower impacts to ESS and MS with both smaller and larger mesh sizes. Under conditions of moderate exploitation, the fraction of MS was significantly larger if small meshed gillnets were used. This is due to the relatively smaller cumulative vulnerability from small mesh sizes through time, as they target a smaller size range of fish, which also grow more quickly through the vulnerable window due to higher growth rates. Therefore, unlike trawls and beach seines, which select all size classes beyond the minimum length of capture (L_c), small meshed gillnets are not necessarily destructive and may rather promote sustained production by allowing a higher proportion of the spawning biomass to remain in the stock. The work also helps to explain the observation of sustained fish production in many developing countries despite the persistent use of gillnets of small mesh size that target small, under‐sized individuals.     

Environmental threats and conservation implications for Atlantic salmon and brown trout during their critical freshwater phases of spawning,egg development and juvenile emergence

Atlantic salmon Salmo salar L. and brown trout Salmo trutta fario L. are species of high socio-economic and ecological value. Declining populations make them target species of fisheries management. This paper reviews the direct effects of deficient longitudinal connectivity, changes in discharge, high water temperatures, oxygen depletion, changes in water chemistry and increasing loads of fine sediment on the critical life stages of spawning, egg incubation and emergence. It further provides an overview about the basic autecological requirements of Atlantic salmon and brown trout and summarises important thresholds of physico-chemical tolerances. This collection of information provides important baselines for assessing historical, ongoing and new threats relevant for the management of both species in fresh waters. Critical early-life stages of both species are almost identical, creating synergies in conservation and restoration. Seaward-migrating forms are exposed to further stressors, but improving starting conditions can also greatly improve their resilience.     

Changes in Sperm Production,Sperm Motility,and Composition of Seminal Fluid in Caspian Brown Trout,Salmo trutta caspius,Over the Course of a Spawning Season

This study was carried out to evaluate milt quality in male Caspian brown trout (Salmo trutta caspius) over the course of the winter spawning season. Milt samples were collected biweekly during December and January. Chemical composition of seminal fluid, sperm production (milt volume, sperm density, spermatocrit,) and sperm motility characteristics (percentage and duration of motility) were measured. Milt volume, sperm density, osmolality, seminal minerals (Ca²⁺, Mg²⁺, K⁺, Na⁺, Cl^?), and total protein gradually decreased over the spawning season. Glucose and triglyceride content of milt did not show significant changes over the spawning season. Milt pH and the percentage and duration of motility were comparatively stable, declining only at the end of the season. Significant positive correlations were found between sperm density and seminal minerals, total protein and spermatocrit; percentage of motile spermatozoa and seminal minerals, total protein; and duration of motility and K⁺, Cl^?, total protein, and pH. Results show that season has a significant influence on milt quality in male Caspian brown trout, with the best milt being available at the beginning of spawning season.     

Efficacy of Vaccination Against Streptococcus iniae During Artificial Spawning of the Red-Tail Black Shark (Epalzeorhynchos bicolor,fam. Cyprinidae)

Artificial spawning may precipitate high mortalities of red-tail black shark (Epalzeorhynchos bicolor) broodstock from Streptococcus iniae infection. Two vaccine formulations (aluminum or oil adjuvant) were evaluated for effectiveness. Fish (mean weight 21.2 ± 5.7 g) were harvested, acclimatized, and vaccinated by intracoelomic injection. After 21 days, fish were moved to a biosecure laboratory and, one day later, simultaneously spawned and challenged by bath or by intracoelomic injection with S. iniae. Both formulations increased relative% survival (RPS) in unspawned (RPS [formulation]: 80 [aluminum]; 54 [oil]) and spawned fish (87–95 [aluminum]; 73–75 [oil]), suggesting that vaccination increases survival of red-tail black shark broodstock after spawning.     

泥鳅激素浸泡催产试验的初报

为了寻找一种简易的泥鳅催产方法。浸泡催产激素有绒毛膜促性腺激素(HCG)、促黄体素释放激素类似物(LHRH-A2)和地欧酮(DOM),以HCG250 IU+LHRH-A22 μg+DOM1 mg/尾为基本剂量(X),食盐作为浸泡助渗剂,食用色拉油为消泡剂。分别进行不同浸泡时间、浓度和盐度的泥鳅催产试验。累计激素浸泡催产种鳅13.987 kg,900尾,获受精卵80.218万粒,其催产率在0%~100%,平均催产率为34.66%;得泥鳅水花苗71.42万尾。孵化率为在45.6%~93.3%之间,孵化率平均值为81.21%。激素浸泡催产率高达80.0%,激素浸泡催产获得泥鳅受精卵的孵化率和注射激素催产获受精卵的孵化率差别不大,说明利用激素浸泡泥鳅催产方便省时,是一种有前途的新方法。浸泡催产激素有绒毛膜促性腺激素（HCG）、促黄体素释放激素类似物（LHRH-A2）和地欧酮（DOM）,按照HCG250IU+LHRH-A22μg+DOM1mg/尾基本剂量（X）;食盐为浸泡助渗剂,食用色拉油为消泡剂。2011年6月15日至20日,笔者分别进行不同浸泡时间、浓度和盐度的泥鳅催产试验。累计激素浸泡催产种鳅13.987kg,900尾,获受精卵84.826万粒,其催产率在 0.00%～80.0%,得泥鳅水花苗71.42万尾。孵化率为在45.6%～93.3%之间,孵化率平均值为81.21%。     

美国白蛾各虫态发育历期试验观察

在恒温25℃、相对湿度75%,光照周期L∶D=16∶8条件下,观察美国白蛾各生态发育历期,结果显示,饲喂杨树叶片处理的各虫态平均历期为:幼虫期24.6～25.3d;蛹期12.3～19.0d;羽化-交尾1.8～2.5d;交尾-产卵期1.8～3.3d;产卵-孵化期8.0～8.5d。饲喂杨树叶片较饲喂家蚕饲料和924-1利于缩短美国白蛾发育周期和增加产卵量。     

Genetic diversity within sea trout population from an intensively stocked southern Baltic river,based on microsatellite DNA analysis

Sea trout, Salmo trutta L., populations in the Slupia River basin have been affected by mass stocking with smolts and fry. This work is focused on a small‐scale differentiation in sea trout populations from one basin with a strong emphasis on the relationship between wild and hatchery origin fish. A total of 216 sea trout were genotyped at 10 microsatellite loci. Global F_ST obtained by amova was low at 0.0165. Pairwise F_ST were significant for all tests except wild and stocked adults. The highest pairwise difference was found between the hatchery sample and Kwacza (F_ST = 0.038). Analysis of the genetic structure revealed micro‐geographical differentiation with four subpopulations. The quality of the artificial spawning was found not to be adequate with a high risk of adverse effects to the whole population. All future stocking actions in the basin should consider the existing population structures.