泉州湾浮性鱼卵和仔、稚鱼的种类和数量分布

根据2001-2002年在泉州湾海域分别进行4个季度月的调查资料，研究分析泉州湾鱼卵和仔、稚鱼的种类组成，数量和主要种类的分布。结果表明，本海区共出现鱼卵和仔、稚鱼34种，分别隶属于14科21属。在数量上，鱼卵和仔稚鱼最高值均出现在春季(5月)，其中鱼卵数量最大的种类是鳀科鱼类，约占总卵量34．2％。仔稚鱼则以鱚科鱼类最为丰富，占61．8％。在数量分布上，不论鱼卵或是仔、稚鱼均以9号站最为密集。这表明该区鱼类主要产卵期在春季。     

伏季休渔的必要性及其效果

南海伏季休渔时间为６月１日零时至７月３１日２４时止。东海、黄海分别于６月１６日零时和７月１日零时正式开始、今年是东、黄海第五年伏季休渔。伏季正是经济鱼类产卵的高峰期,如带鱼的产卵高峰期在每年４～１０月,大黄鱼在每年的２～６月、９～１１月、小黄鱼在每年的３～５月。这一时期禁渔,避免了对产卵群体的破坏。伏季休渔对保护夏季产卵的鱼类群体起到了重要的作用．保证了带鱼、大黄鱼、小黄鱼和鲳鱼等经济鱼类的正常产卵、孵化．同时使仔稚鱼能够安全生长发育。由于伏季体渔彻底限制了对幼鱼资源严重破坏的渔具及捕鱼方式,使…     

利用海带育苗池培育黑鲪苗及苗种的疾病防治

将在近海捕获的１４尾黑亲鱼放在海带育苗池内进行流水培育，让其自然产仔。共产健康仔鱼３６１４００尾，产仔率达２８．５７％。以小球藻、轮虫、卤虫幼体、少量海捕天然浮游动物和鱼、虾肉糜为系列饵料，培育２０～３０天，育出全长１４．２～３０ｍｍ的稚鱼３２２１９８尾，平均成活率８９．１５％；单位水体平均出苗量为６７１２尾／ｍ３。在１８～２４℃水温范围内，仔稚鱼的平均日增长量约为０．５ｍｍ。每３～５天轮流使用１ｍｇ／１的氯霉素，０．３ｍｇ／ｌ的鱼虾安，可以有效地防治仔稚鱼的细菌性疾患；用０．０５ｍｇ／ｌ的孔雀石绿药浴１５～２０分钟，可以防治真菌疾患。     

福建东山湾鱼卵、仔稚鱼种类组成及其丰度时空分布

本文根据2008年5月(春季)和8月(夏季)在东山湾(23°43 ′41″～23°52 ′05″N,117°28 ′27″～117°34′05″E)开展鱼卵、仔稚鱼的凋查资料,分析和讨论东山湾鱼卵和仔稚鱼的种类组成、丰度的时空分布状况.结果表明:本调查海区已分析鉴定的鱼卵仔稚鱼24种,其中16种鉴定到种,4种鉴定到属,4种鉴定到科,还有2种未能鉴定;春、夏两季东山湾鱼类生殖活动频繁,海区出现大量的鱼卵、仔稚鱼;鱼卵、仔稚鱼数量以脂眼鲱(Etrumeus teres)、金色小沙丁鱼(Sardinella aurita)、青鳞小沙丁鱼(Sardinella zunasi)、少鳞鱚(Sillago japonica)和白姑鱼(Argyrosomus argentatus)等经济鱼类为多;春季鱼卵密集区主要分布于东山湾中西部近岸水域,夏季鱼卵密集区分布在东山湾口塔屿附近水域;与福建其他海湾相比较,东山湾是洄游性经济鱼类重要的卵场所之一.     

虹鳟鱼的人工繁育技术

虹鳟鱼俗称鳟鱼,属鲱形目鲑亚目鲑科鳟鱼属,原产于北美州的太平洋沿岸溪流中,属于底层冷水性鱼类.虹鳟鱼雄性性成熟早于雌性.虹鳟鱼雄鱼性成熟一般在2～4年,雌鱼性成熟在3～5年,通常成熟雄鱼以2龄、雌鱼以龄居多.虹鳟鱼孵化对条件要求较严格,虹鳟鱼卵在孵化时应避免强光刺激和外来环境的干扰,所以受精卵孵化应尽可能在室内进行,孵化室面积可根据生产苗种的量来决定.培育数百万尾稚鱼,孵化室在200 m2左右即可.另外,育种孵化室应靠近水源,水质一定要清洁,无污染.池底应高出地面,便于水和污物的排出.延长每天的光照时间可促使产卵期提前,但是不应超过12 h.在平均水温过高的水体中,虹鳟的性腺也会不能按期成熟,不仅会出现异常卵,而且卵的发眼率显著下降.受精卵孵化的水温的范围6～13℃,最适水温为8～10℃.在水温10℃时,孵化期为30d左右.     

杂交石斑鱼(褐点石斑鱼♀×清水石斑鱼♂)仔、稚鱼的摄食与生长特性

为阐明人工育苗条件下褐点石斑鱼♀×清水石斑鱼♂杂交子代(简称杂交石斑鱼)仔、稚鱼阶段的摄食与生长变化状况,采用随机取样实验生态学方法,在水温27.5～31°C条件下,对人工培育的杂交石斑鱼仔、稚鱼的摄食及生长进行了研究。结果显示,杂交石斑鱼仔、稚鱼具有较强的摄食能力;仔鱼3日龄开口摄食,摄食发生率为40%,之后的仔、稚鱼摄食发生率均为100%。仔、稚鱼摄食量随体质量的增加而逐渐上升,可用二项方程式表达。消化道饱满系数为0.95%～11.26%。仔、稚鱼在1.5 h内可以饱食,仔鱼对轮虫和桡足类的消化时间分别为0.5～1 h和1～2 h,稚鱼对桡足类成体的消化时间为1.5～3.5 h。杂交石斑鱼仔、稚鱼各阶段的日摄食率分别为49.85%(5日龄)、22.55%(10日龄)和15.72%(24日龄),可将其作为杂交石斑鱼仔、稚鱼日投喂量参考依据。杂交石斑鱼仔、稚鱼摄食具有明显的昼夜节律性,白天摄食,夜间不摄食。5日龄和10日龄仔鱼均出现2个摄食高峰,分别为9:00和18:00;24日龄稚鱼仅在中午12:00出现摄食高峰。3～30日龄的仔、稚鱼平均全长日增长率为7.96%,平均体质量日增重率为28.73%。全长、体质量分别与日龄的关系均可用指数方程表达,体质量(y)与全长(x)的回归方程为y=0.037 3x2.537 8,b值接近3,表明杂交石斑鱼仔、稚鱼为等速生长类型。     

提高虹鳟鱼种成活率的试验

一、材料和方法１．试验材料（１）鱼池孵化槽为５０厘米×３００厘米×２５厘米的丹麦槽，内置小槽为４５厘米×４５厘米×２５厘米，孵化共用８只丹麦槽，孵化室仔鱼池为０．９米×１０米的条形池，深度为４０厘米，试验池和对照池各两个。稚鱼培养池为３米×２０米的条形池，深度为４０厘米，试验池和对照池各４个。（２）水源、水量亲鱼用水为湖水、涌泉水的混合水，常年水温变化在２～２０℃之间，年平均水温为１２℃，注水量为３．３升／秒，孵化用水也是混合水，水温控制在６～１１℃之间，平均水温为８℃，稚鱼池为涌泉水，常年水温…     

双棘黄姑鱼人工育苗技术的研究

对双棘黄姑鱼催产、孵化和育苗技术进行了试验,并观察描述了其仔、稚鱼及幼鱼早期发育的主要特征.通过对饵料强化及水质控制等育苗关键技术的改进,在水温24.5～28.5℃、盐度26～30的条件下,共培育出平均全长30.92 mm的鱼苗约2.45×105尾.     

室外高位池鞍带石斑鱼人工育苗的初步试验(下)

2.仔、稚、幼鱼培育结果受精卵孵化出仔鱼第3天,投喂小型轮虫后,解开孵化袋使仔鱼进入育苗池塘中。仔鱼进入池塘第2天,在池塘四个角落可见到个别仔鱼游动,随着天数的增加,池塘四周游动仔鱼也有所增多。仔鱼下塘16～21天(仔鱼19～24日龄),仔鱼开始变态为稚鱼。仔鱼变态为稚鱼期间,均出现大     

高体鰤胚胎及仔稚幼鱼的形态观察

本文报道了高体（Ｓｅｒｉｏｌａｄｕｍｅｒｉｌｉ）受精卵的胚胎发育及仔稚幼鱼形态特征。在水温２２～２７℃范围内,受精卵随水温升高,孵化时间缩短。水温２３℃,经过３５ｈ１０ｍｉｎ,仔鱼破膜而出。初孵仔鱼全长为２．９２～３．１２ｍｍ;孵化后３天仔鱼开口,全长为３．８８～３．９８ｍｍ;孵化后２３天,稚鱼全长为１．００～１．３０ｍｍ,鳞片开始形成,鳍棘、鳍条均已分化形成;孵化后３２天,全长为２．０５～２．５６ｍｍ,幼鱼发育完全,体形和成鱼基本相似。     

The effects of survey design and circulation pattern on the perceived abundance of herring larvae: a case study for Norwegian spring spawning herring (Clupea harengus)

A larval survey is used in the annual assessment as an index of the spawning stock size of Norwegian spring spawning herring (Clupea harengus). To test how inter‐annual fluctuations in circulation pattern, survey design and execution of the survey affected the larval abundance estimate we conducted simulated surveys using a model framework with idealized assumptions to model larval drift and sampled larvae using several realistic survey scenarios. The results suggest that inter‐annual variations in circulation pattern alone can have a profound effect on the perception of larvae abundance and that the direction of the survey (north to south versus south to north) can have a significant effect on the estimated abundance, particularly if hatching occurs over a short period of time. Additionally, disruptions to a continuous survey schedule also have an effect and, as such, sampling strategies in case of disruption to the survey are proposed.     

A study of spring-and autumn-spawned herring (Clupea harengus L.) larvae in the Norwegian Coastal Current during spring 1990

An intensive sampling program for yolk-sac herring larvae and microzooplankton was carried out in the main spawning area of Norwegian spring-spawning herring during March to April 1990 (between 62^o and 63^o30'N) to estimate their hatching period and the abundance of copepod eggs and nauplii. Additional investigations were carried out in the Skagerrak area during January-March and on the Norwegian Shelf in May to study the otolith microstructure of the herring larvae. In May both autumn- and spring-spawned herring larvae were found in the samples from the Norwegian Shelf. They were easily distinguished by differences in otolith microstructure. The pattern in increment widths in the otoliths of the autumn-spawned larvae indicated that these larvae had not been transported through the Skagerrak area, but more likely were carried directly from the northern North Sea across the Norwegian Trench and into the Norwegian Coastal Current system. The calculated hatching of the spring-spawned larvae sampled in May occurred significantly later than the observed hatching over the spawning grounds. The results suggest a mismatch between the abundance of first-feeding herring larvae and their prey organisms, resulting in a higher survival of those herring larvae hatching during the latest part of the spawning period. This coincides with a general increase towards the middle of April in the abundance of prey organisms, from 1 to 4 1^_1. There were no differences in otolith microstructure among spring-spawned herring larvae sampled on the shelf in May, indicating that these larvae originated from the same cohort and were well mixed throughout the whole shelf area.     

Lobster larval transport in the southern Gulf of St. Lawrence

A bio‐physical semi‐Langrangian model was developed to follow the drift and abundance of lobster larvae from hatching to settlement as post‐larvae. The geographic domain encompasses Northumberland Strait and the areas surrounding Prince Edward Island in the southern Gulf of St. Lawrence. The model was run for ten larval seasons, 1983–87 and 1997–2001, representing two periods of egg production. The model was forced with tides, winds, heat fluxes, and marine and freshwater fluxes at open boundaries. Biological inputs were location, date, and density of larvae at hatching, development rates, a time window and a minimum bottom temperature required for successful settlement, and two scenarios of daily mortality. Net drift was west to east but stronger on the north than the south side of Prince Edward Island. The hatch was greater in the second 5‐yr period, but the spatial patterns of settlement were similar. For both mortality scenarios, the same five of the 24 larval source areas were important in providing settlers. Horizontal shear of larval distribution indicates fishing communities were dependent on the hatch from fishing grounds of multiple upstream communities. Variation in daily and annual post‐larval settlement was greatest north of Prince Edward Island. From the 24 source areas there was an eightfold range in the fraction of larvae surviving to settlement, with advection into deep water an important cause of mortality. Four to five possible fishery management areas were identified using multidimensional scaling to group sink areas having shared source areas. We hypothesize leaky discontinuity in connectivity between these groups.     

Predicting early life connectivity of Antarctic silverfish,an important forage species along the Antarctic Peninsula

The early life stages of the Antarctic silverfish (Pleuragramma antarctica), an important prey species for higher predators in the Southern Ocean ecosystem, dominate the larval fish assemblages of the Bransfield Strait, one of the most important areas for larval retention off the Antarctic Peninsula. Nevertheless, the spatial location of areas where they were spawned and the timing of larval hatching remain unknown. By linking Lagrangian particle tracking simulations with age data obtained using otolith microincrements from fish caught north of Joinville Island in a pelagic survey, we estimated the distribution of hatch dates and subsequent growth rates of silverfish reaching the Bransfield Strait, and predicted the areas where they were spawned. Larval hatching peaked during the last week of December, and the inner shelf and shelf break, east of the Larsen Ice shelf, were the dominant areas predicted to contribute to larval assemblages in the Bransfield Strait. Over simulated periods of 600–630 days, 35–40% of particles remained within the Bransfield Strait, suggesting an important source of supply to higher predators feeding off the northern Antarctic Peninsula. The daily growth rate at the mean size of 22.3 mm was 0.18 mm, corresponding to a daily change in size of approximately 0.82% standard length (SL), and large variability in growth rate suggested a wide range of environmental conditions experienced during the period of advection from the spawning areas. These results provide spatial predictions that can be tested empirically in future studies, using the simulated trajectories to inform sampling design and spatial coverage.     

条斑星鲽人工繁育技术研究

对条斑星鲽人工繁育技术,孵化适温、适盐范围及亲鱼、仔稚鱼营养强化进行了研究,探讨了温度、盐度、营养强化与性腺、胚胎、胚后发育的关系。结果表明:采用先降温再升温+营养强化方法促熟亲鱼可获得优质卵子。最适孵化温度(10.5±0.5)℃,最适孵化盐度33.6。以小球藻强化轮虫有助于提高仔鱼开口率、生长率及成活率。     

Early Larval Growth of Pacific Halibut Hippoglossus stenolepis

Growth of Pacific halibut Hippoglossus stenolepis larvae was studied in the laboratory during 1989 and 1991. Larvae increased in length from 6.3 mm at hatching to 9.9 mm 20 d post-hatch. The average daily length increment was 0.17 mm. Dry weight of the larvae increased from an average of 210 μg at hatching to 570 μ g on day 20, providing a specific growth rate of 4.99. During the same period, mean yolk sac weight decreased from 1,390 μ g to 646 μ g, resulting in a yolk to body conversion efficiency of 48.5%. At hatching, the larval body made up only 13% of total dry weight. On day 20, the larval body made up 46.9% of the total weight. Larvae started feeding at a length of 12 mm after about 90% of their yolk sac had been absorbed.     

Hatching time effect on the intra‐spawning larval morphology and growth in Northern pike (Esox luciusL.)

Based on the analysis of 11 morphometric variables of body (total length, body area and perimeter, myotome height and eye diameter) and yolk sac (length, height, area, perimeter and volume) of pike larvae, the aim of this study was to evaluate how larval size at hatching and growth of larvae hatched from single egg batches vary according to three hatching times: early, mid and late. Hatching time structures strongly pike larval morphometrics. Early hatched larvae have smaller body sizes at hatch, faster growth and higher yolk use efficiency than late hatched ones. Early hatched larvae seem to be premature and hatch at precocious developmental stage whereas late hatched individuals continue their growth within the egg shell and hatch at larger size but with lower reserves (yolk). A compensatory growth phase was observed for the early hatching pike larvae particularly during the first 5 days post hatch. Consequently, no significant difference in body parameters was recorded from day 10 post hatching whatever the hatching time. The higher growth accomplished by early hatched larvae may be related to a particular metabolic activity that converts more efficiently yolk into body tissues.     

Patchiness structure and mortality of Pacific saury Cololabis saira larvae in the northwestern Pacific

Patchiness structure and mortality rates of Pacific saury Cololabis saira larvae were estimated in the frontal area of the Kuroshio Extension in spring 2000 and 2001. Drogued GPS buoys, which were used as Lagrangian reference points, were deployed to mark dense patches of saury larvae and a series of samplings was conducted using a neuston net around the buoys during the night over a period of several days. A total of 225 tows were conducted and 11 690 specimens were sampled during four buoy tracking. Despite the occurrence of water diffusion, patchiness density, distance between adjacent patches and patch size estimated by geostatistical analysis did not drastically change during the buoy tracking and these parameters were robust for the difference of variogram models and the threshold larval density defining patchiness. Such a stability of the patchiness allowed the estimation of larval mortality from the decrease of larval density for different size classes with respect to individual growth based on the samples taken repeatedly during the buoy tracking. Although low or negative values were obtained for the larvae right after hatching, probably due to continuous hatching, the estimates of mortality then increased and became stable in the range of 23–37% day⁻¹ with a small standard deviation until their knob length reached to 36 mm. In situ information on the patchiness structure and larval mortality provides crucial parameters for simulating the recruitment process of small pelagic fishes in high-resolution hydrodynamic models.     

Factors influencing Saprolegnia spp. spore numbers in Norwegian salmon hatcheries

A quantitative survey of Saprolegnia spp. in the water systems of Norwegian salmon hatcheries was performed. Water samples from 14 salmon hatcheries distributed along the Norwegian coastline were collected during final incubation in the hatcheries. Samples of inlet and effluent water were analyzed to estimate Saprolegnia propagule numbers. Saprolegnia spores were found in all samples at variable abundance. Number of spores retrieved varied from 50 to 3200 L^?1 in inlet water and from 30 to >5000 L^?1 in effluent water. A significant elevation of spore levels in effluent water compared to inlet water was detected. The estimated spore levels were related to recorded managerial and environmental parameters, and the number of spores in inlet water and temperature was the factor having most influence on the spore concentration in the incubation units (effluent water). Further, the relative impact of spore concentration on hatching rates was investigated by correlation analysis. From this was found that even high spore counts did not impact significantly on hatching success.     

Interannual variability in hatching period and early growth of juvenile walleye pollock, Theragra chalcogramma, in the Pacific coastal area of Hokkaido

Juvenile walleye pollock of the Japanese Pacific population were collected from the Funka Bay [spawning ground; 16–64 mm fork length (FL)] in spring and the Doto area (nursery ground; 70–146 mm FL) in summer. Hatch dates were estimated by subtracting the number of otolith daily increments from sampling dates, and their early growth was back‐calculated using otolith radius–somatic length relationships. Interannual change of the hatching period was observed during 2000–02, and the peaks ranged from mid‐February in 2000 to early‐April in 2002. In 2000, when a strong year class occurred, early life history of the surviving juveniles could be characterized by early hatching and slower growth in the larval stage (<22 mm length). Higher growth rate in 2001 and 2002 did not always lead to good survival and recruitment success. Even though their growth was slow in 2000, the larvae hatched early in the season had larger body size on a given date than faster‐growing larvae hatched in later season in 2001 and 2002. Bigger individuals at a certain moment may have advantage for survival. The delay of hatching period may result in higher size‐selective mortality, and as a necessary consequence, back‐calculated growth in 2001 and 2002 could shift towards higher growth rate, although abundance of such a year class would be at the lower level. Variability in spawning period, early growth and their interaction might have a strong relation to larval survival through cumulative predation pressure or ontogenetic changes in food availability.