南湾水库翘嘴红鱼白的生长及种群控制的研究

南湾水库的翘嘴红舶体长与体重实测值的关系呈幂指数关系，关系式为：W=0．0489L^2.7274(r^2=0.9739)。应用Von Bertalanffy生长方程拟合其生长规律，体长与体重的生长不等速，其主要生物学参数为：L∞=98．8cm，W∞=7140．9g。体长的k=0．1662、t0=0．2638；体重的k=0．1038、t0=-0．1076，拐点年龄t1=5．3龄，拐点体长为57cm，体重为2049g。建议翘嘴红舶的捕捞年龄为2^ ，即体长为28cm、体重为500g以上，其适用网具的网目为90mm。     

南湾水库翘嘴红鲌的生长及种群控制的研究

南湾水库的翘嘴红鱼白体长与体重实测值的关系呈幂指数关系,关系式为:W=0.0489L2.7274(r2=0.9739)。应用VonBertalanffy生长方程拟合其生长规律,体长与体重的生长不等速,其主要生物学参数为:L∞=98.8cm,W∞=7140.9g,体长的k=0.1662、t0=0.2638;体重的k=0.1038、t0=-0.1076,拐点年龄ti=5.3龄,拐点体长为57cm,体重为2049g。建议翘嘴红鱼白的捕捞年龄为2+,即体长为28cm、体重为500g以上,其适用网具的网目为90mm。     

南湾水库鳙鱼的生长及其资源评估

南湾水库的鳙鱼的平均年龄为3龄,南湾水库鳙鱼体长与体重的关系呈幂指数关系,关系式为W=0.0413L2.8472(R2=0.9422)。应用VonBertalanffy生长方程拟合其生长规律,体长与体重的生长不等速,其主要生物学参数为:L∞=87.6cm,W∞=28.5kg,体长的k=0.2443、t0=0.26778;体重的k=0.141、t0=-0.137,拐点年龄ti=7.5龄,拐点体重为8.05kg。回捕率37.5%,自然死亡率27.0%,其它死亡率33.3%。南湾水库鳙鱼的适宜开捕年龄为3 龄,平均体重约3947g。适当减小起捕规格,提高捕捞强度,可增加鲢鳙鱼的产量和效益。     

丝蝴蝶鱼年龄与生长的初步研究

对海南海区采得的51尾丝蝴蝶鱼(Chaetodon auriga Forstal)年龄与生长的研究表明,其年轮特征主要为切割型,体长(L)与鳞径(R)呈直线相关:L=-3.5730+6.8387R;体长(L)与体重(W)呈幂函数的关系:W=5.9540×10-2L2.8126.应用Von Bertalanffy生长方程拟合该鱼的一般生长规律,其生长参数为:L∞=23.25cm,W∞=420.77g,K=0.2777,t0=-0.1579,拐点年龄ti=4龄,拐点体长Li=15.92cm,拐点体重Wi=135.14g.海南海区丝蝴蝶鱼应以2龄、体长10.26cm、体重46.23g为最适合可捕标准.     

乌江思南泉水鱼的年龄与生长研究

2011-2012年在乌江思南江段采集454尾(雌性298尾,雄性109尾,性别不辨47尾)泉水鱼(Pseudogyrincheilus procheilus),以鳞片作为材料对年龄进行鉴定,利用软件FISAT-II处理体长与年龄数据,对其生长方程、生长拐点等生物学特征进行了研究。结果表明,泉水鱼鳞片为圆鳞,年轮主要表现为普通切割型与普通疏密型;年龄组成为1~4龄,其中以2~3龄为主;1~4龄,体长增长率为47.4%,雌性体长增长率达50.4%,雄性体长增长率为35.0%,体重增长率为438.5%,雌性体重增长率为485.1%,雄性体重增长率为275.9%;体重(W)与体长(L)呈幂指数关系:W=2×10-6L3.4784(R2=0.8824),雌鱼为:W=3×10-6L3.4002(R2=0.8505),雄鱼为:W=2×10-5L3.019(R2=0.8112);体长(L)和鳞径(S)呈幂函数相关:L=92.597S0.5458;Von Bertalanfy生长方程的各参数为:渐进体长L∞=278.10 mm,生长系数k=0.22,t0=-1.80;雌鱼各参数为:L∞=355.01 mm,k=0.14,t0=-2.38;雄鱼各参数为:L∞=224.04 mm,k=0.32,t0=-1.72,雄鱼达到渐进体长的速度比雌鱼要快得多;体长生长速度和加速度不具拐点,生长速度随年龄增加而递减,生长加速度始终为负值,随年龄增加而增大;体重生长速度和加速度都具有拐点,拐点年龄ti=3.87,拐点体长Li=198.22 mm,拐点体重Wi=195.59 g。结合泉水鱼生长拐点年龄和性成熟年龄,为保护乌江思南泉水鱼资源,建议以180 mm为最小捕捞个体的体长。     

闽东北外海渔场银方头鱼Branchiostegus argentatus(Cuvier)渔业生物学初步研究

闽东北外海底层流刺网作业渔获的银方头鱼群体由Ⅰ-Ⅺ龄11个世代构成，以Ⅱ、Ⅲ和Ⅳ龄占优势；体长优势组为210-270mm，体重优势组为200-400克，体长与体重的关系W=2.1120×10-5×L2.9964，r=0.9970。初次性成熟年龄为Ⅱ-Ⅲ龄，最小性成熟个体体长为190mm，在4-8月均有产卵活动；按VonBantanffy方程拟合生长参数L∞=436.21mm，W∞=1715.05g，K=0.2357，t0=-0.9542，体重生长拐点年龄为3.702龄。     

黑龙江细鳞斜颌鲴鱼生长的研究

本文研究了镜泊湖细鳞斜颌鲴的年龄与生长。通过对细鳞斜颌鲴鳞片上形成的年轮鉴定和退算，镜泊湖细鳞斜融鲴的1龄鱼体长为5．5cm；2龄鱼12．6cm；3龄鱼18．2cm；4龄鱼23．1cm；5龄于26．8cm；6龄鱼29．0cm。体重与体长的相关表达式为：w=0.01287513.0553,r=0.999。根据Von.Bertalanffy的生长方程的理论公式运算，其生长参数：L∞=40.8cm;W∞=1024g;-k=0.244;to=0.332,r=0.998.tip=5.2龄；Tmax＝13．7龄。     

丝蝴蝶鱼年龄与生长的初步研究

对海南海区采得的51尾丝蝴蝶鱼(Chaetodon auriga Forstal)年龄与生长的研究表明,其年轮特征主要为切割型,体长(L)与鳞径(R)呈直线相关:L=-3.5730+6.8387R;体长(L)与体重(W)呈幂函数的关系:W=5.9540×10-2L2.8126。应用Von Bertalanffy生长方程拟合该鱼的一般生长规律,其生长参数为:L∞=23.25cm,W∞=420.77g,K=0.2777,to=-0.1579,拐点年龄ti=4龄,拐点体长Li=15.92cm,拐点体重Wi=135.14g。海南海区丝蝴蝶鱼应以2龄、体长10.26cm、体重46.23g为最适合可捕标准。     

岳阳中洲渔场鳙鱼年龄与生长的研究

根据2002年对岳阳中洲鱼场费家湖鳙鱼的取样调查分析,对该湖泊中鳙鱼的年龄生长进行了初步研究,计算出其体长与鳞半径相关为L=4.4285+14.0799R,体长与体重的关系式为W=3.2415×10-5L2.8759。确定其Von-Bertalanffy生长方程,得出其生长参数为L∞=78.3316詐,W∞=9.0682詔,K=0.2089,t0=-1.497a。通过其生长速度和加速度曲线反映生长过程的变化特点,确定了其生长拐点ti=3.76a,对指导生产和捕捞有重要意义。     

线纹尖塘鳢的池养生长特性与幼成鱼饲养研究

对人工繁殖的线纹尖塘鳢幼、成鱼进行连续29个月的池养饲养,观测其生长结果。结果表明,该鱼生长旺期在2龄鱼,年内生长呈现阶段性;体长与体重关系式为W=0·02L3·0754,属等速生长型鱼类。应用von Berta-lanffy方程,对连续饲养6龄鱼求得其体长、体重生长方程分别为Lt=48·4317[1-e-6·3099(t 0·4826)],Wt=3515·5347[1-e-0·3099(t 0·4826)]3·1312,体重生长拐点于3·2龄处,属衰老拐点。全长2·7～3·2cm幼鱼经第1年的网围、池塘、越冬池等分级中间培育,养成全长15～17·5cm幼鱼,成活率43·5%～58·3%;再经第2年的养成,个体重达300～750g,成活率92%～98%,单产1～1·8kg·m-2。     

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.