Validation of a method of estimating age, modelling growth, and describing the age composition of Coilia mystus from the Yangtze Estuary, China

A collection of 577 Coilia mystus was made during April 2006 and 2007 from China's Yangtze Estuary to estimate the age structure and growth patterns of the population. Examination of sectioned sagittal otoliths revealed a periodic straight/curved growth pattern. The straight zone was from April to November, and the curved zone from October to May, indicating annual periodicity. Annual periodicity was also verified by margin zone analysis. The shift from a curved-zone to the next straight-zone stanza was defined as an annulus. The fish from which the otoliths were taken were 0-5 years old. The von Bertalanffy growth function was fitted to standard length (LS)-at-age data as L-S = 215.16 (1 - e(-0.53(t+0.30))) (n = 577, r(2) = 0.81, p < 0.05). The mature females included five age classes, ages 1 and 2 accounting for 74.3% of the population. The mature males included fish aged 1 and 2, those at age 1 accounting for 86.4% of the population. Mean length was smaller, and annual growth less, for mature males than for females of comparable age. The study demonstrated that the Yangtze population of C. mystus consists of more age classes than previously thought and that the age structure of the population needs to be considered in management decisions.

长江口及其邻近海域鱼类浮游生物群落结构特征研究

本文根据1999年－2007年间7个航次的长江口及其邻近海域的鱼类浮游生物和环境因子的调查资料，探讨了三峡工程蓄水前后长江口鱼类浮游生物群落特征，主要包括长江口鱼类浮游生物的种类组成、数量变动、群落多样性、空间分布格局等，分析了三峡工程蓄水前后长江口鱼类浮游生物群落结构的动态变化，为评价三峡工程对河口生态环境及鱼类补充资源的影响提供科学依据，研究结果如下： 1．三峡工程蓄水前春季（1999年5月和2001年5月）共捕获11540个鱼类浮游生物隶属11目18科32种，其中凤鲚(Coilia mystus)、鳀(Engraulis japonicus)、六丝矛尾鰕虎鱼(Chaeturichthys hexanema)、白氏银汉鱼(Allanetta bleekeri)、松江鲈(Trachidermis fasciatus)为优势种；鱼类浮游生物群落可划分为三个类群：①以凤鲚为优势种的河口群组，②以松江鲈和白氏银汉鱼为优势种的沿岸群组，③以鳀和六丝矛尾鰕虎鱼为优势种的近海群组；盐度、深度、溶解氧和悬浮体是影响这一海域鱼类浮游生物分布的主要环境因子。 2．三峡工程蓄水后春季长江口的环境因子总体分布格局没有改变，部分环境因子表现出数量上的差异：溶解氧含量偏低，COD平均值下降，pH值显著上升，盐度升高，河道水域和口门附近悬浮体下降，长江口鱼类生物群聚栖息环境发生了变化。三峡工程蓄水后春季（2004年5月和2007年5月）共采获的25种鱼类浮游生物，总丰度(1 070个)仅为蓄水前(11 540)的10%，4种优势种白氏银汉鱼、凤鲚、松江鲈和鳀贡献了总丰度的94.57％；蓄水后影响长江口鱼类浮游生物格局的主要环境因子是盐度和悬浮体，蓄水后长江口鱼类浮游生物群聚类型(河口型、沿岸型和近海型)与蓄水前一致，但沿岸型空间分布区域明显减少，近海型分布区域向河口方向扩展。长江口环境因子中，盐度和悬浮体是蓄水前后鱼类浮游生物群聚变异的主要影响因素。 3．三峡工程蓄水前后春季四次调查共记录鱼类浮游生物39种，生态类型包括淡水、半咸水、沿岸和近海。春季长江口鱼类浮游生物优势种包括鯷、凤鲚、白氏银汉鱼、松江鲈和六丝矛尾鰕虎鱼，2004年和2007年鯷、凤鲚优势地位有所下降。长江口鱼类浮游生物群落结构年度间差异显著，以2004年长江口鱼类浮游生物群落结构与1999和2001年相异性最高，鯷和凤鲚种群数量变动对其群落变异的贡献率最大，群落相似性以2004和2007年最高，达71.17%。与蓄水前相比，三峡水库蓄水后的长江口鱼类浮游生物群落多样性显著下降。1999—2007年间，长江口发生了一系列环境环境条件变化，直接或间接的环境干扰带来了长江口鱼类生物群落结构变异。 4．2007年四个航次（春、夏、秋、冬）共捕获鱼类浮游生物6,463个, 隶属12目28科45种, 以鳀科丰度最高, 占总丰度的76.5%。长江口鱼类浮游生物包括4种生态类型: 淡水型(2种), 半咸水型(14种), 沿岸型(10种)和近海型(16种)。其中, 近海型物种个体数量最多, 占2007年长江口鱼类浮游生物总丰度的74.55%。鳀在4个季节均有出现, 对长江口鱼类浮游生物丰度贡献最大。鱼类浮游生物在物种组成上存在明显的季节变化: 白氏银汉鱼在春季占绝对优势, 鳀是夏季优势度最高的种类, 秋季除鳀外, 前颌间银鱼(Hemisalanx prognathus)成为优势种; 鱼类浮游生物丰度高度集中在优势种上, 各季节优势种对总丰度贡献超过89%。群落物种数量、丰度、丰富度指数、均匀度指数和多样性指数, 在夏季最高, 春季和秋季次之, 冬季最低。2007年长江口鱼类浮游生物的群落格局在空间上分为三个不同的群组：河口、沿岸、外海，并且这种分布随长江冲淡水的季节变化而变化。盐度是影响决定长江口鱼类浮游生物群落空间分布的最重要因子，而温度则是影响其季节性结构变化的主要因子。此外，生殖洄游和索饵洄游也是影响鱼类浮游生物群落结构时间变化的重要因子。

Polyculture of gulsha (Mystus cavasius Ham.) with rajpunti (Puntius gonionotus Bleeker) and silver carp (Hypophthalmichthys molitrix Val.) in earthen ponds

Culture of gulsha (Mystus cavasius) with rajpunti (Puntius gonionotus) and silver carp ( Hypophthalmichthys molitrix) was undertaken to assess the growth and production potential of these species under polyculture system. Fingerlings of gulsha, rajpunti and silver carp were stocked at a density of 18.000, 10.000 and 4.000/ha respectively. Two treatments were tested in this experiment. Treatment-I was conducted with rice bran and mustard oil cake and treatment-II with rice bran and duck weed. All the ponds were fertilized with urea and TSP at fortnightly intervals. After six months' rearing, the gross production was estimated to be 3,582 and 3,125 kg/ha from treatment-I and treatment-II respectively. Total yield showed non-significant differences (P>0.05) between the treatments.

Morphometry and length-weight relationship of Coilia dussumieri, Valenciennes, 1848 from Mumbai waters

Coilia dussumieri Valenciennes, 1848 a component of 'dol' net fishery forms an important pelagic resource along northwest coast of India. The present communication deals with morphometry and length-weight relationship of this species along Mumbai coast. Morphometric study showed a positive correlation among the compared characters. The length-weight relationship for the species from Mumbai coast was found to be W=0.017L super(2.4223).

Indices and fecundity of a threatened freshwater catfish Mystus montanus

Fecundity of threatened catfish Mystus montanus was estimated from a collection of gravid females, which ranged from 290 to 27,972 according to body length and weight. The relationship between fecundity and BL, BW, GL and GW was analyzed by linear regression, which showed both positive and negative correlation. Gonado-somatic index (GSI), hepato-somatic index (HSI) and spleen-somatic index (SSI) ranged from 0.135 to 21.28, 0.358 to 21.33 and 0.126 to 1.08 in females and the corresponding values for males were 0.17 to 10.68, 0.619 to 3.25 and 1.25 to 2.33 respectively.

Effect of lykamin on growth and biochemical composition of long whiskered catfish, Mystus gulio (Hamilton) fingerlings under laboratory conditions

A growth trial was conducted to test the effect of Lykamin (dietary supplement) on growth, survival and feed conversion in Mystus gulio. Four isoproteic diets were formulated by incorporating the growth promoter, Lykamin at the levels of 0, 0.25, 0.50 and 0.75% diet. The crude protein content was 30% in each diet. The diets were fed to triplicate groups of catfish fingerlings twice daily at a level of 5% of the total body weight for 120 days. Regular fortnightly sampling was done to evaluate the growth performance of the experimental animals. Water quality parameters during the experimental period were maintained within the range suitable for catfish. The results showed better specific growth rate, weight gain, protein efficiency ratio and feed conversion ratio in the group which was given 0.75% Lykamin diet.

Culture potentials of gulsha (Mystus cavasius) in management under different stocking densities

PLEASE ALSO CHECK THE FULL TEXT ABSTRACT. Semi-intensive grow-out trials on monoculture of gulsha (Mysrus cavasius) were conducted to assess the production potentials for the period of six months from March through August 2002. Three stocking densities such as 40,000 (T-1), 50,000 (T-2) and 60,000/ha (T-3) were tested in three replications. The production of gulsha was 1,~·74±52, 1,535±71 and 1,370±60 in treatment-I, 2 and 3, respectively and they were significantly different (p

Food of two size-groups of the catfish Mystus giulio (Hamilton-Buchanan) in Vemblai canal, Vypeen Island

The stomach contents of two length-groups of the catfish Mystus gulio collected from Vemblai Canal in Vypeen Island (Kochi) were examined by frequency of occurrence and points methods. Analyses using standard indices proved difference in diet composition between the two size-groups.

Spawning behaviour and induced breeding of an estuarine catfish, Mystus gulio (Ham.)

Spawning behaviour of hormone induced estuarine catfish, Mystus gulio was observed in captive condition. Spawning activities that include pairing, chasing and resting, nudging, and twisting, started about 5 hours post injection and ended with release of eggs within 1-2 hours of courtship. Three different dosages of "ovaprim" (1 ml/kg, 1.5 ml/kg, and 2 ml/kg in a single dose) were used in induced breeding of M gulio. The latency period was less (6-7 hours) with the dose of 1.5 and 2 ml/kg, while it was more (7-8 hours) with that of 1 ml/kg. However, all females spawned successfully with each of three different dosages, without any significant differences in the rate of fertilization and hatching. Eggs under all hormone dosages hatched between 18-20 hours after spawning. The hatching rate with 1, 1.5, and 2 ml/kg varied from 71.3-72.7%, corresponding to the fertilization rate of 80.7-84.7%.

Effects of stocking density on growth and survival of Mystus gulio in nursery ponds

A study on the effect of stocking density on growth and survival of nona tengra (Mystus gulio) was carried out in brackishwater earthen nursery ponds (2 decimal each) for a period of 42 days. Five-day old captive bred tengra post-larvae (ABL: 4.53±0.83 mm and ABW:3.33 mg) were stocked at four different densities of 200/m² (Treatment-1), 250/m² (Treatment-2), 350/m² (Treatment-3) and 450/m² (Treatment-4). Fries were fed twice a day with a mixture of fine rice bran, mustard oil cake and fishmeal at the ratio of 2:1:1. The specific growth rate (SGR) of larvae did not vary significantly (p>0.05) between T1 (5.096% mg/day) and T2 (5.08% mg/day), but it was found significantly (p<0.05) higher from T3 (4.98% mg/day) and T4 (4.91% mg/day), respectively. The final survival rates of 89.25±5.41% in T1 and 88.72±6.09% in T2 were found similar (p>0.05), but significantly higher (p<0.05) than those of, 76.20±4.77% in T3 and 70.34±5.71% in T4. The results indicate that 5-day old hatchery bred nona tengra post-larvae can be nursed in earthen pond at a stocking density of 200-250/m².

Embryonic and larval development of Mystus gulio (Ham.)

Mystus gulio eggs are strongly adhesive and contain relatively small yolk (0.75-1.0 mm). The egg envelop is thick and transparent. First cleavage (two cells), four cells, eight cells, sixteen cells and multi cells stages were found 20, 25, 35-40, 60 and 70 minutes after fertilization, respectively. The morula stage was visualized within 1.5 h after fertilization. The heart beat visible and the circulatory system commenced after 16 h of fertilization. Embryos hatched 18-20h after activation of egg. The newly hatched larva measured 2.82±0.03 mm in length and 0.32±0.06 mg in weight. The yolk sac was fully absorbed by the third day though larvae commenced exogenous feeding even before completion of yolk absorption. A 5-day old post larva began wandering in search of food. Ten-day old post larvae endowed with eight branched rays in dorsal fin and seven in caudal fin. Fifteen-day old post larvae had the pectm:al spine become stout though the embryonic fin folds had to be disappeared. The length of fingerlings ranged from 25-30 mm after 30 days, and their external features were just like those of an adult except that they were not sexually matured.

Gonad development of an anadromous fish Coilia ectenes (Engraulidae) in lower reach of Yangtze River, China

Anadromous Coilia ectenes was sampled from the Yangtze estuary at Chongming and two of the primary upstream spawning grounds at Jingjiang and Anqing in April, May, June and August 2006. Gonad development was analyzed for females. In April, fish were collected in the estuary and at Jingjiang, but not at Anqing. No female was mature (gonad at stages IV or V) at either location. In May, 45% of the females were mature in the estuary, 9% at Jingjiang and 5% at Anqing. In June, 86% were mature in the estuary, 83% at Jingjiang and 7% at Anqing. In August, C. ectenes was absent at Jingjiang. No female was mature in the estuary, and all females were mature at Anqing. Absolute fecundity (AF) increased significantly with standard length (SL) by a power function AF = 2.27 x 10(-6) x SL2.67 (r(2) = 0.57, n = 48, P < 0.05). Mature females in the estuary were smaller than those at Jingjiang and Anqing. Conservation of spawners in the upstream spawning grounds is important because they have a size-related fecundity advantage over the smaller spawners in the estuary.

Studies on fish epidemics from Assam

Investigations conducted since July 1988 on ulcerative fish epidemics in Assam, India, indicated that mainly four species of fishes belonging to the genera Puntius, Channa, Macrognathus and Mystus were widely affected by the disease. Results indicated that outbreak of the disease may not be due to organic pollution of water or radioactive and heavy-metallic contamination. Bacterial culture revealed colonies of Escherichia coli and Pseudomonas aeruginosa in the surface muscular lesions and gill tissues while preliminary electron microscopic studies indicated the presence of viruses in the muscles and gills of diseased fishes.

Food and feeding habits of Megalaspis cordyla (Linnaeus, 1758) along the northwest coast of India

Megalaspis cordyla as one of the shoaling commercially important pelagic fish in the Northwest coast of India. The study on food and feeding habits of this fish revealed that it is predominantly a carnivorous species feeding primarily on sergestied shrimps like Acetes indicus and small fishes such as Stolephorus species. In addition it feeds on juveniles of Trichiurus, Apogon, Coilia, Sardinella, Nemipterus, Thryssa, and sciaenids. The food of M. cordyla also comprises the young ones of molluscs, especially Loligo and Sepia and occasionally ostracods. The choice food is Acetes indicus.

Biodiversity in floodplains with special reference to artificial stocking

A five years investigation on fish biodiversity in connection with artificial stocking was conducted in three south-western floodplains of Bangladesh from 1992 to 1996. The ten top most available and ten rarest fish species were identified. Puntius sp., Channa punctatus, Mystus sp., Anabus testudinius, Ambasis sp., Colisha sp. and Macrobrachium sp. etc. were the most common available species. On the other hand, Mystus aor, Notopterus chitala, Clupisoma garua, Aplocheilus panchax, Ctenophmyngodon idella etc. were the rarest species. However, the most abundant and the rarest fish species behaved differently in different floodplains in different years. Shannon diversity index was used to assess the extent of diversity in different years. The study revealed that the artificial stocking programme, to some extent, influenced the biodiversity in floodplains.