虾池浮激植物初级生产力的研究

用黑白瓶测氧法对辽宁省庄河青堆水产公司虾池整个养殖期间（５－９月）浮游植物初级生产力进行研究。虾池浮游植物的初级生产力为（５．４５±２．３６）ｇＯ２／（ｍ＾２．ｄ），日Ｐ／Ｂ系数为２．３９（０．６７－６．６６），浮游植物对太阳有效辐射的利用率为０．７８（０．２４－２．１８）％，浮游植物毛产量到虾产量的转化效率为７．４１％；回归分析表明，浮游植物生物量和太阳有效辐射量是决定虾池浮游植物初级生产力大小     

报刊要闻

<正> 虾池初级生产力 用黑白瓶测氧法对辽宁省庄河青堆水产公司虾池整个养殖期间(5～9月)浮游植物初级生产力进行研究。虾池浮游植物的初级生产力为(5.45±2.36)gO_2(m~2·d),日P/B系数为2.39(0.67～6.66),浮游植物对太阳有效辐射的利用率为0.78(0.24～2.18)％,浮游植物毛产量     

乳山湾6—9月叶绿素a含量的分布及初级生产力的估算

根据1995年6～9月对乳山湾东流区进行的6次综合调查结果，着重阐述了乳山湾东流区叶绿素a含量的分布特．点及其与海洋环境因子的关系，并对初级生产力进行了估算。结果表明，乳山湾东流区对绿素a含量6～9月份平均值为11．16mg／m3，最高值出现在9月中旬，高达45．26mp／m3；估算初级生产力的平均值为432m星C／m2·d；在影响叶绿素a含量分布与变化的环境因子中，与浮游植物细胞数量、温度、径流和营养盐等关系密切；乳山湾东流区叶绿素a含量和初级生产力处于较高的水平。     

东港湖浮游植物现存量及生产量

东港湖浮游植物主要有47种，隶属于7门38属。优势种春秋季为绿藻和硅藻，夏季为黄丝藻，冬季为甲藻。浮游植物数量秋季最多（232．45×104个／L）。生物量冬季最高（3．664mg／L．）叶绿素a夏季最高（5．35ug／L）。初级生产力夏季最高（3．13gO2／m2·d）。光和效率夏季最高，种群兴起春季最盛。湖水属中营养型。浮游植物提供的滤食性鱼产潜力为2．966万kg。     

轮虫培育池不同粒级藻类对浮游植物生物量和生产量的贡献

研究了流水轮虫培育池(14^#)、静水轮虫培育池(15^#)和轮虫饵料培养池(11^#)中不同粒级浮游植物，特别是超微藻类对浮游植物叶绿素和初级生产力的贡献。结果表明，在14^#池中，超微藻类、微型藻类和小型藻类的叶绿素a含量分别占总叶绿素a含量的3．7％、82．9％和13．4％。各粒级浮游植物初级生产力分别占总生产力的13．6％、66．0％和20．4％。在11^#池中，超微藻类、微型藻类和小型藻类的叶绿素a含量分别占总叶绿素a含量的4．5％、16．1％和79．4％。各粒级浮游植物初级生产力分别占总生产力的9．0％、78．9％和12．1％。在15^#池超微藻类、微型藻类和小型藻类的叶绿素a含量分别占总叶绿素a含量的4．7％、22．3％和73．0％。各粒级浮游植物初级生产力分别占总生产力的12．4％、60．8％和27．8％。水体中的初级生产力主要是由微型藻类提供，占总量的60．8％～78．9％，在轮虫培育池生态系统中微型藻类是主要生产者。     

莺河一库渔业潜力及开发对策

对莺河一库水质的调查分析和饵料生物的定量测定得出：该库属中营养型水库，浮游植物初级生产力平均２３．９６ｋｇＯ＿２／ｈａ·ｄ，其中鱼类生长期内初级生产力３２１．１６ｋｇＯ＿２／ｈａ·ｄ，净生产量２５．７３ｋｇＯ＿２／ｈａ·ｄ，净生产量之和为５４０３．３ｋｇＯ＿２／ｈａ，折合浮游植物鲜重为２８６３７．５ｋｇ／ｈａ；浮游植物、浮游动物和底栖动物的生物量分别为３．２ｍｇ／Ｌ、１．２６ｍｇ／Ｌ和０．８５ｇ／ｍ￣２，水库近期鱼产力为３６３．６ｋｇ／ｈａ，总产量２０．９４万ｋｇ。该库历年平均成鱼单产为８８．４ｋｇ／ｈａ，占估算鱼产力的２４．３％，水库的渔业潜力有待开发利用，因此，提出了今后合理开发水库渔业资源的对策。     

蛤蟆通水库浮游植物初级生产力及能量转化效率的研究

本文论述1991－1993年对蛤蟆通水库游游植物初级生产力和能量转化效率的测定结果。蛤蟆通水库浮游植物初级生产力，日产量达4．420－8．490go2/m^2，水柱年产量达574．6－1103．76go2/m^2。浮游植物初级生产力与浮游植物的现存量、水温、PO4－P等有显著关系。其能量转化效率平均为0．54％，属中等水体。     

养鳗池塘的初级生产力和能量转换效率

报道了养鳗池塘初级生产力的垂直变化和季节变化。养鳗池塘的初级生产量为 3.5 1～ 7.90gO2 /m2 ·day ,高峰通常出现在 7～ 8月。 1米以上水层的光合作用产氧量占水柱总产量的 90 %以上。平均补偿深度为 6 5～ 74cm。池水氧气的消耗 ,池鱼占 2 7.4% ,“水呼吸”占 70 .0 % ,底泥占 3.6 %。浮游植物光合产氧占池塘氧气来源的 6 6 .0 % ,余下的 43.0 %靠空气和加水补给。毛初级生产力对太阳辐射能的利用率为 0 .38%～ 0 .85 % ;鳙产量对浮游植物的利用率为 1 .0 5 %～ 2 .32 % ;太阳能转移为鱼产量的生态学效率为 0 .0 0 9%～ 0 .0 1 0 %。     

南美白对虾高位池浮游生物和初级生产力的研究

4口试验虾池共检出浮游植物32属(种),隶属于7个门,浮游植物生物量变化在2.15～83.24mg/L,平均为30.41mg/L。虾池浮游植物的多样性指数相对较低,平均为0.202。试验虾池共检出浮游动物23种,生物量变化在0.45～6.34mg/L,平均为3.38mg/L。各试验虾池浮游植物和浮游动物生物量平均数相差不大,但各月份的生物量差别较大。浮游植物生物量呈现波动式上升;浮游动物生物量表现为由高到低,再由低到高的变化趋势。试验虾池水柱毛初级生产量变化在2.03～12.54g/m2·d,平均6.58g/m2·d;呼吸量变化在1.24～12.05g/m2·d,平均5.89g/m2·d。试验虾池P/R有很大的波动,变化在0.9～2.21,平均1.27。     

EDTA-Na_2直接滴定乳中总钙及方法的评价

对20份乳样用EDTA－Na2直接滴定Ca含量，结果在1．25mol／lKOH中为1．18±0．19（mg／ml），在1mol／lNaoH中为1．14±0．19（mg／ml）；用食品中钙测定的标准方法测定结果为1．12±0．26（mg／ml），两法之间无显著差异（P＞0．2和P＞0．5）。直接滴定法重复试验结果的CA为3．43％；回收率为102．15％±3．92％（97．44％～107．69％），说明直接滴定法可用于乳中总钙测定。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of diatom–bacteria biofilm isolated from Seriola lalandi cultures for aquaculture application

Controlled incorporation of selected microalgae and bacteria in aquaculture systems can be beneficial because they can act as microbiological control. That is why the characteristics of biofilm generated naturally in Seriola lalandi culture cages were analysed, their potential benefit to the growth of larvae was studied, and their controlled use for improving the larval viability and as a vector to improve incorporation of previously studied probiotic bacteria was tested. According to biodiversity results, these biofilms are composed of a diatom–bacteria mix showing a decrease in biodiversity in laboratory culture conditions being dominated by Navicula phyllepta and bacteria of the family Rhodobacteraceae. This can be produced on mesh substrates incorporated in bioreactors with rapid growth rate and adhesiveness. Preliminary results from the addition of substrates with this specific biofilm in larvae culture systems showed that it is consumed by the larvae without negative effects, while positive effects on the viability of larvae in combination with probiotics were observed. Considering preliminary results, the addition of these specific substrates with diatom–bacteria biofilms could be a good improvement for aquaculture systems and together with the use of probiotics can contribute to maintaining a stable and controlled system improving the viability of the larval fish culture in its early stages.