Yellow perch strain evaluation I: Genetic variance of six broodstock populations

As a prelude to strain selection for domestication and future marker assisted selection, genetic variation revealed by microsatellite DNA was evaluated in yellow perch, Perca flavescens, from four wild North American populations collected in 2003-2004 (Maine, New York, North Carolina, and Pennsylvania,), and two captive populations (Michigan and Ohio). For the loci examined, levels of heterozygosity ranged from H-e=0.04 to 0.88, genetic differentiation was highly significant among all population pairs, and effective migration ranged from low (N(e)m=0.3) to high (N(e)m=4.5). Deviation from Hardy-Weinberg equilibrium was regularly observed indicating significant departures from random mating. Instantaneous measures of inbreeding within these populations ranged from near zero to moderate (median F=0.16) and overall inbreeding levels averaged F-IS=0.18. Estimates of genetic diversity, Phi(ST), and genetic distance were highest between Michigan and all other broodstock groups and lowest between New York and Ohio. Genetic differentiation among groups did not correlate with geographic distance. Overall, the patterns of variation exhibited by the captive (Michigan and Ohio) populations were similar to patterns exhibited by the other wild populations, indicating that spawning and management practices to date have not significantly reduced levels of genetic variation. (C) 2007 Elsevier B.V. All rights reserved.

大西洋庸鲽Hippoglossus hippoglossus和大西洋鲑Salmo salar配子质量研究

种质问题是养殖健康发展的基础。在鱼类养殖中，卵子和精子的质量直接关系到受精、胚胎发育，仔稚鱼发育以及幼鱼生长等一系列过程。本论文针对大西洋庸鲽和大西洋鲑的配子质量进行研究。研究内容涉及大西洋庸鲽精子冷冻保存方法；促性腺激素释放激素类似物（GnRHa）使用对其精子冷冻保存效果、以及脂肪酸组成的影响；野生和驯养大西洋鲑卵子在脂肪酸、类胡萝卜素、矿物盐方面的差异比较。 精子冷冻保存通过提高对精子的利用效率，进而对于种质改良，推进鱼类养殖科研和生产具有重要意义。本实验建立了大西洋庸鲽精子大容量冷冻保存方法。八种抗冻剂冷冻保存实验结果表明：10% 及15% DMSO配以 HBSS 或KS 的抗冻剂组合冷冻保存效果最佳，4 mL体积冷冻保存可获得与1.6 mL同样的保存效果。 在繁殖季节后期注射GnRHa激素缓释剂，可获得质量稳定的大西洋庸鲽精液，将激素注射方法与精子冷冻保存方法相结合对于提高雄鱼利用率，扩大生产规模具有重要实用价值。本项研究分三个时间采集注射GnRHa激素后的雄鱼精子以及同期未注射激素的雄鱼精子，对所有精子样品使用同样的方法进行冷冻保存，检测冷冻保存后解冻精子的受精率与活力。结果表明，激素注射与否对于冷冻保存后精子的受精率和活力无显著影响，两类冷冻精液均达到鲜精水平。实验结果还表明，注射激素14天后的精子的密度显著的降低。说明GnRHa激素的使用可以显著降低精子密度，但不会影响精子的冷冻保存效果。 本相研究同时对注射GnRHa 缓释激素和未注射GnRHa 缓释激素的大西洋庸鲽精液脂肪酸成分进行分析，以检测该激素使用对精子生化组分的影响。结果表明激素的使用对在DHA (22:6n-3,二十二碳六烯酸)、EPA(20:5n-3,二十碳五烯酸)、AA(20:4n-6，花生四烯酸)等重要脂肪酸，不饱和脂肪酸、饱和脂肪酸以及n-3、n-6等重要种类的脂肪酸总量及其比例没有显著影响。精液脂肪酸中DHA含量最高，约占25%；PUFA约为44%。 作为世界性的重要养殖品种，野生和驯养大西洋鲑在形态、生化组成以及遗传 等方面表现出的差异被广泛关注。本论文，对野生和驯养大西洋鲑受精卵关键生化成分进行分析，通过与野生受精卵比较阐明驯养受精卵的质量状况，为亲鱼营养需求提供指导依据。本实验中野生配子和驯养配子的受精率没有显著差异，但重要脂肪酸组成、类胡萝卜素以及矿物盐含量都存在多方面显著差异。两类受精卵脂肪酸中含量最高的依次为18:1n-9（油酸）、DHA（二十二碳六烯酸）、16:0（棕榈酸）、EPA（二十碳五烯酸）。野生受精卵的单不饱和脂肪酸总量显著高于驯养受精卵，而多不饱和脂肪酸（PUFA）比例显著低于驯养的受精卵。在主要必需不饱和脂肪酸（EFA）中，DHA和EPA在野生受精卵中的比例高于驯养受精卵，AA（花生四烯酸）低于驯养受精卵。野生受精卵虾青素（Ax）的含量低于驯养受精卵而鸡油菌素（Cx）含量高于驯养受精卵。野生受精卵中多种矿物盐的含量（铝、铜、铁、硒和锌）含量显著高于驯养的受精卵。差别最大的为铜。诸多方面的差异表明，野生亲鱼与驯养亲鱼产出的卵子确实存在显著差异，因此关注亲鱼的营养极为重要。

Effects of effective population size on the F-2 growth and survival of bay scallop Argopecten irradians irradians (Lamarck)

In 2002, six cohorts of broodstock bay scallop Argopecten irradians irradians (Ne=1, 2, 10, 30, 50 and control) were randomly chosen from a population of bay scallop to produce offspring. After one year rearing, with the progeny matured, the similar experiment was done to produce the F-2 generation. To determine the magnitude of Ne effects, the growth and survival rates in larvae and adult of six F2 groups were compared. Results showed that inbreeding depression existed not only in the Ne=1 group but also in the Ne=2 group. The growth and survival rates of the two groups were significantly lower than those of the other groups (Ne=10, 30, 50, control), and there were no significant differences among the latter (P>0.05). At the same time, the amount of depression in the Ne=1 group was significantly higher than that of the Ne=2 group (P<0.05). These results indicated that the low effective population size (Ne), which increases the possibility of inbreeding, could lead to some harmful effects on the offspring. So it is essential to maintain a high level of Ne in commercial seed production. Furthermore, as the high fecundity of bay scallop might lead to increased inbreeding, selecting broodstock from different growout sites is recommended.

A new three-phase culture method for Manila clam, Ruditapes philippinarum, farming in northern China

Studies on reproduction, hatchery management, and culture of Manila clams Ruditapes philippinarum were carried out in an attempt to optimize their culture conditions and techniques. Results from these studies led to the development of a three-phase culture method for Manila clam farming in northern China. The key components of the new method were: 1) early spawning and over-wintering indoors (greenhouse); 2) optimized larval culture conditions and techniques; 3) juvenile rearing in shallow, fertilized nursery ponds; 4) optimized stocking size and density and substrate for mudflat grow out. Broodstock were maturated indoors for a month from early April to early May. Primarily because of higher water temperatures in the greenhouse the clams spawned more than one month earlier than in the natural environment. From May to July, juveniles were reared for 1-2 months indoors to a size of 2.0-3.0 mm in shell length before being moved to outdoor, pre-disinfected, nursery ponds. Juveniles were then reared in the nursery ponds for one month to about 1.0 cm before being transferred to the mudflat for grow out. Juvenile clams in nursery ponds grew considerably faster than in the natural environment probably because of higher temperatures and more abundant natural food. During grow out, the clams were reared for 4-7 months until they reached a market size (3.0-3.3 cm). Juveniles produced after August were over-wintered in the greenhouse in which the water temperature was about 3 degrees C higher than that of the outdoor environment. Juveniles grew at an average rate of > 20 mu m day(-1), while in the natural environment no growth was observed during winter because of low temperatures. Juveniles in the greenhouse grew to 2-3 mm by the following March before being moved into outdoor nursery ponds. The three-phase culture method not only shortened the production period from spawn to market size from 24-36 months to about 10-14 months, but also prolonged the spawning season from 2 to 7 months, resulting in increased production of seed and market-size clams. Compared with the traditional method, the new method could increase the yield of market-size clams by 10-11 times, and increase the profit per ha mudflat by as much as 124 times and the profit per kg market-size clams produced by 13 times. (c) 2006 Elsevier B.V. All rights reserved.