Factors influencing the efficacy of MS-222 to striped mullet (Mugil cephalus)

Some responses of juvenile striped mullet (Mugil cephalus) to the anesthetic MS-222 were investigated. Induction times to total loss of equilibrium decreased with increasing anesthetic concentration over the range of 40–120 ppm. Temperature, pH, and oxygen concentrations all significantly affected induction times to total loss of equilibrium in freshwater-adapted fish at a concentration of 80 ppm MS-222. Anesthetic toxicity was less for saltwater-acclimated fish than for freshwater-acclimated fish. The 24-h 50% mortality (LC₅₀) in fresh water was 33.1 ppm; in salt water it was 39.8 ppm. The results suggest that anesthetic action may be intensified in fish acclimated to conditions other than those near their physiological optima.     

Studies on the biology of young grey mullet, Mugil cephalus L. II. Food and Feeding

This is the second of a series of investigations into the biology of young grey mullet, Mugil cephalus L., and the feasibility of its culture in the coastal, estuarine waters of Sri Lanka. The food and feeding habits of mullet, 20–55 mm in length, from the coastal Negombo Lagoon (7° 10′ N; 79° 50′ E) were studied from November 1974 to October 1975.The feeding intensity, estimated as the number of food organisms found in stomachs per feeding individual, followed a seasonal pattern with the intensity increasing from April onward and reaching a peak during June–August. Over 80% of the individuals were found to feed throughout the year. The diet consisted of 18 genera of diatoms, eight genera of green algae, some desmids, six genera of blue-green algae and eight other food groups. No sand or detritus was found to occur in fish smaller than 25 mm in length, and the percentage occurrence of detritus and/or sand particles increased with increase in body length. Quantitatively and qualitatively, diatoms were the most predominant food items, accounting for more than 50% of the total diet. Although only one genus of Xanthophyceae was found to occur in the diet, its contribution was significant.M. cephalus was found to show diurnal periodicity in feeding activity; peaks of activity occurred at dawn and around midday and were unrelated to the state of the tide.The significance of the nature of the diet and the occurrence of two peaks of feeding activity within a 24-h period is evaluated in the light of present knowledge of the food and feeding behaviour of M. cephalus at various stages of growth, and the possibilities of polyculture with other herbivorous species is discussed briefly.     

The culture of striped mullet (Mugil cephalus Linnaeus) in ponds receiving heated effluent from a power plant

During 1972 and 1973, striped mullet (Mugil cephalus Linnaeus) were stocked into six ponds (located on the upper end of the Galveston Bay system, Texas, U.S.A.) receiving heated effluent. Fish were fed commercially prepared feeds. In 1972, mean daily weight and standard length gains in two ponds were 0.71 and 0.66 g and 0.65 and 0.59 mm. In 1973, mean daily weight and standard length gains in four ponds were 0.64, 0.36, 0.67, and 0.59 g and 1.03, 0.81, 0.71, and 0.67 mm. During the two year study, survival rates ranged from 50 to 85%; production, from 293 to 804 kg/ha. Food conversion fluctuated from 2.24 to 3.31; commercial feed costs, from $0.61 to $0.87 per kg of fish.     

不同溶氧变动模式对鲻生长、能量代谢和氧化应激的影响

为研究不同溶氧变动模式对鲻生长、能量代谢和氧化应激的影响,实验设计5种溶氧变动模式,分别为一直维持正常溶氧N处理(7.0 mg/L)、正常溶氧-低氧变动N-L处理(7.0→1.5 mg/L)、超饱和溶氧-正常溶氧变动S-N处理(14.0→1.5 mg/L)、超饱和溶氧-正常溶氧-低氧变动S-N-L处理(14.0→7.0→1.5 mg/L)和一直维持超饱和溶氧S处理(14.0 mg/L).实验选择初始体质量为(16.07 ±0.11)g的鲻,在循环水装置中养殖56 d,然后测定其特定生长率、鲻血浆、肌肉、肝脏和鳃组织的乳酸(LD)含量、过氧化物歧化酶(SOD)活力、总抗氧化能力(T-AOC)、抗超氧阴离子活力(ASOR)、丙二醛(MDA)含量、总谷胱甘肽(T-GSH)、氧化型谷胱甘肽(GSSG)和还原型谷胱甘肽的含量.测定终末体质量为(31.47 ±1.44)g鲻的耗氧率、排氨率和氧氮比.结果显示,5种溶氧变动模式对鲻生长影响显著,N、S和S-N处理的鲻特定生长率显著高于N-L和S-N-L处理.S处理的鲻排氨率和氧氮比显著高于其他处理.5种溶氧变动模式均对鲻氧化应激指标含量影响显著.研究表明,肝脏是主要氧化应激器官.经历低氧变动模式的鲻,代谢速率下降,同时需要消耗较多的物质和能量参与氧化应激,用于生长物质和能量需求减少从而导致生长速度下降.T-GSH含量与氧化压力呈负相关,在应对低氧和超饱和溶氧产生的氧化压力中起重要调节作用.     

Stocking effectiveness of hatchery-released kuruma prawns estimated by two-stage sampling of commercial catch in Ariake Sound, Japan

ABSTRACT:    To evaluate the stocking effectiveness of the kuruma prawn Penaeus japonicus , a two-stage sampling survey of Gensiki bottom-drift-netters was carried out in Ariake Sound, Saga Prefecture, Japan. A total of 471 000 hatchery-produced juveniles, marked by cutting off the right uropods, was released. Thirty-three fishing days were randomly drawn from four boats, which were selected from the 80 boats operating in the fishery. All prawns caught on the selected days were examined, and the hatchery-produced individuals were identified by their regenerated uropods. A telephone survey of all boats was also conducted, to determine the number of fishing days. A total of 286 marked prawns were caught on the survey days for the Saga area in Ariake Sound, from the last half of July to the first half of September 2002. The recapture rate and standard error were estimated at 0.76 ± 0.52%. Economic efficiency was estimated at 0.28 ± 0.02. Strategies for sampling schemes and stock recovery are also discussed.     

Mugil curema in Argentinean waters: Combined morphological and molecular approach

A previously unidentified mullet species (Mugil sp.) from Mar Chiquita lagoon, Argentina, was compared with two candidate species Mugil curema and M. cephalus using 12 truss landmarks and three mitochondrial DNA genes (12S rRNA, cytochrome b and COI). Both procedures confirmed that the Argentinean fish were white mullet M. curema. Morphological comparisons clearly segregated M. curema from M. cephalus samples in PCA plot. Similarly, Argentinean haplotypes at each gene overlapped with M. curema reference samples while M. cephalus haplotypes remained distinct. These combined data provide a valuable baseline for further investigations on the geographic distribution of this commercially important species group.     

肖四海湖五种渔具的鳜渔获结构特征及其对鳜资源的影响

为评估不同渔具对鳜资源的影响,于2007年5月和12月对长江中游浅水湖泊肖四海湖刺网、延绳钓、网簖、电拖网和电捕仪5种渔具捕获的鳜渔获物结构特征进行了调查分析.结果发现,共采集鳜样本359尾,全长分布范围为92 ～600 mm,优势全长集中于251～350 mm;体质量分布范围为10～3 380 g,优势体质量集中于300 ～500 g.种群由5个年龄组构成,2～3龄为优势龄组,占总数的74.6％.刺网、延绳钓和网簖对鳜有较强的捕捞选择性,网目大小为80 mm和100 mm刺网的鳜渔获物中2龄及以上成熟个体占总数的93.3％,个体平均体质量466 g,“标鳜”(0.4 ～0.75 kg)个体占总数量的57.0％;延绳钓捕获的鳜渔获物中2龄及以上成熟个体占总数的86.9％,“标鳜”个体占总数量的43.5％;网簖捕获的鳜渔获物中90％以上为1龄的未成熟个体.电拖网和电捕仪捕获的鳜全长范围明显较大,其渔获物以1龄和2龄个体为主.综合分析表明,刺网适于作为鳜捕捞的主要渔具,延绳钓可以作为一种鳜捕捞的辅助渔具.网簖对鳜补充群体有较大危害,不适于作为鳜的捕捞网具.电拖网和电捕仪均属于违法渔具,对鳜资源危害巨大,应该加大监管力度,严禁使用.     

Identification of additional tilapia from Lake Kinneret,Israel, by the form of their scales

A key is presented which allows identification of Tilapia zillii, Tristramella simonis, Tristramella sacra and Astotilapia flaviijoshephi on the basis of the shape of their scales.     

Identification of four tilapia species from Lake Kinneret,Israel, by the form of their scales

A key is presented which allows identification of Sarotherodon galilaeus, Oreochromis niloticus, O. aureus and the hybrid ♀ O. niloticus × ♂ O. aureus on the basis of the shape of their scales.     

Body composition of Mugil cephalus,Liza dumerili,Liza richardsoni and Liza tricuspidens (Teleostei: Mugilidae) caught in the Swartkops Estuary

Body composition (protein, fat, ash and moisture) and energy content of four mullet species Mugil cephalus, Liza dumerili, Liza richardsoni and Liza tricuspidens were determined monthly for 13 months in specimens taken from the Swartkops Estuary. Six size classes (<2.5, 2.6–6.0, 6.1–10.0, 10.1–15.0, 15.1–23.0 and > 23 cm SL) were analysed separately. Statistical analyses of results could only be performed on three size classes of M. cephalus, L. dumerili and L. richardsoni due to inavailability of fish during certain months. Regression equations were calculated for those body components that were significantly correlated, viz.: energy and moisture, fat and moisture, protein and moisture and energy and fat. The influence of species, size as well as seasonal effects and reproductive cycle on body composition were investigated. It was found that in general Liza dumerili had the lowest mean body energy and fat values and Liza tricuspidens the highest. Smaller size fish were lower in energy and fat and larger size fish lower in moisture. Overall mean values showed that body energy reserves were the highest during the winter. Sexually mature specimens of Liza dumerili showed a build-up of energy before the commencement of the spawning season.     

Extinction of Daphnia lumholtzi (Sars) in Lake Kinneret (Israel)

Daphnia lumholtzi (Sars) was found in Lake Kinneret until the late nineteen-fifties. Lake Kinneret was the northern-most limit of the distribution of this species. It is suggested that fingerlings of grey mullets and Sarotherodon aureus that were introduced into Lake Kinneret caused the extinction of D. lumholtzi.     

淀山湖光泽黄颡鱼食性研究

于2009年8月至2010年7月在上海市淀山湖采集光泽黄颡鱼胃含物样品,采用传统镜检法对其食性进行研究。结果表明:淀山湖光泽黄颡鱼全年均有摄食,且摄食强度存在显著的季节变化,其中饱满指数排序:秋 > 春 > 冬 > 夏,春季空腹率显著高于其他季节;共鉴定其饵料生物7大类(11小类),聚类分析表明,出现率(F%)、数量百分比(N%)和相对重要性指数(IRI%)在衡量食物对光泽黄颡鱼的重要性方面表现一致,重量百分比(W%)与前三者存在显著差异,综合以上4种指数显示,底栖甲壳类、多毛类和水生昆虫是光泽黄颡鱼的主要食物来源;选用W%对其食性进行时空比较,聚类分析显示其冬季食物组成与其他季节存在显著差异,而站点间差异不明显,均以底栖甲壳类为绝对食物来源;食物组成Shannon-Weiner多样性存在明显的空间差异,高低依次为S5 > S3 > S4 > S2 > S1 > S6,研究认为光泽黄颡鱼食性具有较强的地域性和可塑性。     

库克群岛海域海洋环境因子对大眼金枪鱼渔获率的影响

为了掌握库克群岛海域海洋环境因子对延绳钓渔业中大眼金枪鱼渔获率的影响,实验利用2013年9月8日—12月31日在库克群岛海域作业的延绳钓渔业调查数据,所获数据包括:钓钩深度数据,温度、叶绿素a浓度、三维海流的垂直剖面数据,作业参数,渔获统计数据,采用逐步回归的方法建立钓钩预测深度计算模型,利用统计和聚类分析的方法分析大眼金枪鱼渔获率与海洋环境因子的关系。结果发现,在库克群岛附近海域,大眼金枪鱼渔获率较高的水层、温度、叶绿素a浓度、东西海流、南北海流、水平海流和垂直海流分别为120.0～199.9 m、13.0～14.9 ℃、0.200～0.239 μg/L、0.1～0.2 m/s、-0.2～0 m/s、0.1～0.4 m/s和0.04～0.05 m/s。在该海域作业、以大眼金枪鱼为目标鱼种时,建议在大眼金枪鱼渔获率较高的水层、温度、叶绿素a浓度、水平海流和垂直海流范围内增加钓钩投放数量。     

The induced spawning of the grey mullet, Mugil macrolepis (Aguas) Smith and the large-scale rearing of its larvae

The grey mullet, Mugil macrolepis (Aguas) Smith could be induced to spawn by the administration of pituitary alone from the same species. The threshold dose was found to be three and four glands as the first and second injections after a 6-h interval. About 40% of the experiments were successful. The hand-stripped eggs were artificially fertilized with milt by the dry method.The embryonic development of the eggs are briefly described. The majority of the fertilized eggs hatched out about 23 h after fertilization. The salinity of the water ranged from 29 to 31‰ and temperature from 26 to 29°C.A method for the large-scale rearing of mullet larvae is outlined. “Seasoned greenwater” is produced by keeping slightly manured brackish water for about a fortnight in small tanks which can be exposed to sunlight in the afternoon. Blooms of Chlorella sp. developed and the larvae fed on the microplankton. The larvae at about 1 cm in length fed exclusively on copepods. Hence copepod cultures were maintained simultaneously in manured cisterns for feeding the mullet larvae until they accepted artificial feeds.     

大鳞鲃的人工繁殖、胚胎发育和耐盐碱测定

2008-2010年进行大鳞鲃的人工繁殖和胚胎发育观察,并测定了胚胎、仔鱼的耐盐碱能力。结果表明,大鳞鲃是产漂流性卵的鱼类,繁殖性周期为1年产卵1次类型。水温19～23℃时,催产药物的效应时间在21～26 h,1.4～2.3 kg的雌性亲鱼产卵量在8×105～1.4×106粒,人工繁殖的催产率、受精率和孵化率平均为63.9%、81.5%、86.6%。大鳞鲃的卵为灰白色,直径约1.5 mm,遇水后卵膜会迅速吸水膨胀,1 h后达到最大为4.5 mm。水温20～23℃时,从卵授精到仔鱼孵出需要的积温为49.82℃.d,到仔鱼平游摄食需要积温125.14℃.d,刚出膜的仔鱼全长(6.07±0.18)mm,当达到(8.30±0.47)mm开始平游摄食。在耐盐碱实验中,测得大鳞鲃的胚胎72 h在盐度3.2以下、碱度14.32 mmol/L以下的水体中对成活率无影响;仔鱼96 h在盐度5.1以下、碱度14.32 mmol/L以下的水体对成活率无影响。     

Stocking of sea trout, Salmo trutta, in Lake Veere, south-west Netherlands

Lake Veere (1750–2050 ha), a brackish water lake in south‐west Netherlands, is a former branch of the Oosterschelde. The lake was closed off by the construction of two dams in 1961. Since the early 1970s Lake Veere has been regularly stocked for recreational and commercial fisheries with rainbow trout, Oncorhynchus mykiss (Walbaum), brown trout, Salmo trutta L., and glass eel, Anguilla anguilla (L.). Between May and September 1996 an experimental stocking of 18 054 trout of sea trout parentage (15–16 cm; 776 kg) was carried out to study their potential for recreational fisheries. The growth and mortality of the stocked trout were estimated from recaptures in eel fyke nets. The production and consumption of the stocked trout were estimated with a bioenergetics model. After 3.5 years (May 1996–November 1999) the stocked trout measured between 50 and 70 cm. The estimated annual total mortality was 84%. During the winter of 1996–1997, the biomass of the stocked trout reached a maximum of about 1800 kg. By November 1999 the biomass was estimated to be 100 kg. The maximum daily consumption by the trout population was 60 g ha^?1 in October 1996 and in June 1997. The total consumption of the stocked trout population over the 3.5‐year period was estimated as 54 244 kg. The analysis suggested that the stocked trout used about 0.2% of the average annual primary production of the lake system. Although the growth and initial production of the population are attractive from the perspective of a recreational fishery, the high mortality and infestation with the salmon louse, Lepeophtheirus salmonis (Krøyer), are serious drawbacks for a future stocking programme with trout in Lake Veere.     

Food and feeding habits of Tilapia zillii (Gervais) (Cichlidae) in Lake Kinneret (Israel)

Analysis of the gut content of 329 specimens of T. zillii (Cichlidae) collected from Lake Kinneret, has shown great variation in the sorts of food.A study of seasonal dynamics has proved the prevalence in the food of Chironomida pupae (Diptera) in winter and spring and of zooplankton forms in summer and autumn. The additional food consisted of the various groups of algae, the most frequently found being Cyanophyta (100%) and Pyrrophyta (64.16%). An extremely voraceous species, it consumes — while searching for its preferred food — anything that comes its way in the water: algae, scraps of macrophytes, autochthonous and allochthonous insects, and forms of benthic origin, such as Nematoda, Ostracoda, Porifera and Chironomida (larvae).The satiation index is high (between 4.08 and 5.63), in contradiction to the low values of the coefficient of condition (between 3.05 and 3.51), and with the slow rate of growth in Lake Kinneret. The main food of Tilapia zillii, consists of arthropod species with a chitin content (which is eliminated unchanged) of more than 50% of the total weight, and this may account for the poor exploitation of the trophic base.This species of fish may be considered as being detrimental to others (i.e. commercially important species) because of its successful competition for food, and not, as is often incorrectly assumed, because it is an aggressive consumer of their spawn and fry.     

Food and feeding habits of Tilapia aurea (Steindachner) (Cichlidae) in Lake Kinneret (Israel)

An analysis of the food of 274 specimens of Tilapia aurea (Steindachner), which had been collected in Lake Kinneret, showed that this species is mainly a zooplankton consumer.A study of the quantitative dynamics of the food components in the course of a year has proved that the species in question feeds more intensely in spring, this being the time when zooplankton forms are more abundant in the water of the lake. Vegetable detritus, mixed with plankton and benthos forms, served as additional and alternative food.The lack of clearly positive degree of food component selectivity, as well as the low values of the intestine repletion index and of the condition coefficient, account for the slowness in growth of Tilapia aurea in Lake Kinneret.The low values of the growth and feeding indices are due, according to the authors, to the pressure brought to bear by the other local fish species, which are competitors for the same food.