Evidence for fine geographical scale heterogeneity in gene frequencies in yellowfin tuna (Thunnus albacares) from the north Indian Ocean around Sri Lanka

Yellowfin tuna are currently considered by the member nations of the Indian Ocean Tuna Commission to constitute a single stock in the Indian Ocean due to a lack of knowledge about yellowfin tuna population structure in this region. Previous studies of Indian Ocean yellowfin tuna based on morphology and fisheries data have hinted at the presence of multiple stocks in the region, and further, that stocks may mix in the north western Indian Ocean around Sri Lanka. To better understand the genetic stock structure of yellowfin tuna in the north western Indian Ocean, we examined genetic variation in 285 yellowfin individuals collected over a period of 4 years from six fishing grounds around Sri Lanka and a single fishing ground in the Maldive Islands. We screened variation in both the mitochondrial ATPase 6 and 8 region (498 bp) and three microsatellite loci. Significant genetic differentiation was detected among sites for mitochondrial DNA (Φ_ST = 0.1285, P < 0.001) and at two microsatellite loci (F_ST = 0.0164, P < 0.001 and F_ST = 0.0064, P < 0.001), while spatial analysis of molecular variance of mtDNA data identified three genetically heterogenous groups namely; western, south eastern and all remaining sites. These results suggest the possibility that genetically discrete yellowfin tuna populations may be present in the north western Indian Ocean.     

吉尔伯特群岛海域延绳钓渔场大眼金枪鱼的环境偏好

为了掌握基里巴斯吉尔伯特群岛附近海域大眼金枪鱼的环境偏好,2009年9月至12月,金枪鱼延绳钓船"深联成719"在该海域进行了调查。利用仪器获取海洋环境数据,结合每天渔获数据,应用逐步回归方法,建立钓钩深度预测模型,计算大眼金枪鱼在各水层、温度、盐度、叶绿素、含氧量、水平海流和垂直海流范围内的渔获率,渔获率最大的各环境因子范围为大眼金枪鱼偏好的环境。结果表明:(1)大眼金枪鱼偏好的水层、水温、盐度、叶绿素、含氧量、水平海流和垂直海流范围分别为200.0~240.0 m、14.0~15.0℃、35.00~35.10、0.24~0.26μg/L、3.0~4.0 mg/L、0.00~0.20 m/s和0.03~0.04 m/s;(2)一般情况下,接近成熟的大眼金枪鱼偏好的水温为14.0~17.0℃;(3)大眼金枪鱼的适盐性较广;(4)溶解氧高于门限值(0.8 mg/L)时,大眼金枪鱼的分布由其它环境因子决定。     

Comparative growth performances of diploid and triploid Chinese shrimp Fenneropenaeus chinensis (Osbeck, 1765) under different salinities

This study aimed at evaluating the ploidy effects on growth performances of Chinese shrimp ( Fenneropenaeus chinensis Osbeck, 1765) reared in different salinities under laboratory conditions. In the acute salinity experiment, there was no difference ( P >0.05) in tolerance observed in triploid and diploid shrimp due to abrupt salinity changes. The lethal salinity for 50% of the individuals in 96 h at 23–25 °C was about 2 g L⁻¹ in both triploids and diploids. While for the chronic salinity experiment, statistical analyses confirmed that the differences in growth performances including the specific growth rate (SGR), the feeding rate (FR), feed conversion efficiency (FCE) and intermoult period (IP) between triploid and diploid were related to salinity. Diploid shrimp reared in 20 g L⁻¹ exhibited highest SGR ( P <0.05), while triploids performed well in 20 and 30 g L⁻¹ salinities ( P <0.05). Based on the survival and growth data, the optimal salinity for the culture of diploid F. chinensis should be 20 g L⁻¹ and for triploids it should be between 20 and 30 g L⁻¹.     

Anaesthetic efficacy and physiological responses to clove oil-anaesthetized kelp grouper Epinephelus bruneus

The efficacy of clove oil as an anaesthetic and at producing a physiological response (plasma cortisol and glucose) was evaluated in the kelp grouper, Epinephelus bruneus . To acquire complete anaesthesia in less than 3 min and recovery in <10 min, three doses of clove oil were tested at 18, 22 and 26 °C. Although higher anaesthetic doses resulted in shorter induction times and longer recovery times, and a lower temperature resulted in longer anaesthesia induction and slower recovery, we found the optimal dose and administering temperature of clove oil to be 250–300 mg L⁻¹ at water temperature of 18 °C, 150–200 mg L⁻¹ at water temperature of 22 °C and 50–100 mg L⁻¹ at water temperature of 26 °C respectively. Following the administration of 150 mg L⁻¹ of clove oil at 22 °C, the plasma cortisol level was highest (4.24 ± 1.571 μg dL⁻¹) after 12 h and the plasma glucose was highest (92.7 ± 9.61 mg dL⁻¹) after 2 h. These results should be useful to the aquaculture industry, where anaesthesia is necessary for a range of activities.     

An argo‐based experiment providing near‐real‐time subsurface oceanic environmental information for fishery data

A better understanding of the relationships between oceanic environments and fishing conditions could make the utilization of fish more efficient, profitable, and sustainable. The current lack of high‐precision subsurface seawater information has long been a constraint on fishery research. Using near‐real‐time Argo observations, this paper presents a new approach called gradient‐dependent optimal interpolation. This approach provides daily subsurface oceanic environmental information according to fishery dates and locations. An experiment was conducted in the western and central Pacific Ocean using yellowfin tuna (YFT) catch data in August 2017. The results of seawater temperature and salinity represented differences of less than ±0.5°C and ±0.05, respectively, according to verification of error analysis and truth‐finding comparisons. After applying the constructed temperature and salinity profiles, we described the relationship between subsurface information and yellowfin tuna catch distribution. Statistical analysis revealed that yellowfin tuna were more adapted to warmer and saltier seawater. At the near‐surface (<5 m), the most suitable temperature was 28–29°C, although yellowfin tuna can endure a temperature range from 11 to 12°C at a depth of 300 m. The corresponding upper boundary of the thermocline was approximately 75 m, with a mean strength of 0.074°C/m, and the most suitable salinity for yellowfin tuna was 34.5–36.0 at depths shallower than 300 m. These results indicated that the constructed subsurface information was very close to the true values and they had high spatial and temporal accuracy.     

基于集成学习的大西洋热带水域大眼金枪鱼渔情预报

为提高大西洋大眼金枪鱼渔场预报模型的准确率,实验利用13艘中国延绳钓渔船2013—2019年的渔捞日志数据和对应的海洋环境数据(海表面风速、叶绿素a浓度、涡动能、混合层深度和0～500 m水层的垂直温度、盐度和溶解氧等),以天为时间分辨率、2°×2°为空间分辨率、以数据集的75%为训练数据建立了K最近邻(KNN)、逻辑斯蒂回归(LR)、分类与回归树(CART)、支持向量机(SVM)、人工神经网络(ANN)、随机森林(RF)、梯度提升决策树(GBDT)和Stacking集成(STK)渔情预报模型,以25%的测试数据进行模型性能测试、比较。结果显示,(1) STK (由KNN、RF、GBDT模型集成)模型的大眼金枪鱼渔场预报性能较KNN、LR、CART、SVM、ANN、RF和GBDT模型有所提高且相对稳定,上述模型对应的准确率和ROC曲线下面积(AUC)依次分别为81.62%、0.781,79.44%、0.778,72.81%、0.685,74.84%、0.717,73.67%、0.702,67.70%、0.500,80.96%、0.780和78.13%、0.747;(2) STK模型预测...     

Total calcium and inorganic phosphate in the blood plasma of farmed rainbow trout, Oncorhynchus mykiss

Reference (physiological) value intervals determined by the lower 2.5% and upper 97.5% quantiles were calculated for total calcium (Ca _t ) and inorganic phosphate (P) in farmed rainbow trout, Oncorhynchus mykiss , at an age of 10–12 months in raceway culture. Total calcium levels were significantly ( P ≤0.0009) greater in males (2.63–4 mmol L⁻¹, n =47, mean weight 359±142 g) than in immature females (2.48–3.97 mmol L⁻¹, n =410, mean weight 400±145 g). The reference range for P in immature females and males was 3.09–9.32 mmol L⁻¹ ( n =467, mean weight 401±144 g). The distribution and density of the quantiles in the tested reference group were made possible by the use of histograms, which showed normal distributions for Ca _t in males but not for Ca _t and P in immature females and males, in which a sinistral asymmetry was found.     

Use of salt to control ichthyophthiriosis and prevent saprolegniosis in silver perch, Bidyanus bidyanus

The ciliate protozoan, Ichthyophthirius multifiliis , and the fungus, Saprolegnia parasitica , cause the diseases ichthyophthiriosis and saprolegniosis respectively. Both diseases are difficult to control and can cause high mortalities of freshwater fish, including the Australian silver perch, Bidyanus bidyanus (Mitchell). The efficacy of salt (NaCl) in controlling and preventing these diseases in silver perch was evaluated in aquaria and tanks. Low pH levels were also evaluated as a control for ichthyophthiriosis. Concentrations of 2 or 3 g L⁻¹ salt controlled infestations of I. multifiliis , and fish were free of both theronts and trophonts by day 8 at temperatures of 17.3–21.3 °C and by day 6 at 19.2–23.5 °C. Fish treated with 1 g L⁻¹ salt remained infested and all fish in a control treatment (0 g L⁻¹ salt) died. Although the mean survival rates of infested fish at pH levels of 5 or 6 were only 13.9% and 7.6%, respectively, there were no theronts or trophonts on surviving fish after 12 days. Silver perch harvested from a pond and treated with 2 or 3 g L⁻¹ salt did not become infected with S. parasitica and survival was 100%, whereas 16.6% of untreated (0 g L⁻¹ salt) fish became infected and survival was only 66.7%. A concentration of 2 g L⁻¹ NaCl is recommended for the control of ichthyophthiriosis and the prevention of saprolegniosis in silver perch held in tanks, aquaria and re-circulating aquaculture systems.     

Efficacy of tricaine methanesulphonate and clove oil as anaesthetics for juvenile cobia Rachycentron canadum

Six experiments were designed to determine the optimal anaesthetic dosage of tricaine methanesulphonate (TMS) and clove oil that could be used safely on juvenile cobia Rachycentron canadum of two sizes [G1=4.9±0.8 g; G2=13.9±3.1 g]. We documented the stage of anaesthesia and the acute toxicity as 96 h LC₅₀ (lethal concentration 50% population) at various exposure times of the two anaesthetics. At 10 min induction time, the TMS 96 h LC₅₀ was 93.9 mg L⁻¹ in G1 and 97.0 mg L⁻¹ in G2. Compared with clove oil, the 96 h LC₅₀ was 60.0 mg L⁻¹ in G1 and 69.8 mg L⁻¹ in G2. The difference between the two groups (G1, G2) did not influence anaesthesia safety ( P >0.05). Rachycentron canadum achieved stage 3 anaesthesia more rapidly at a lower clove oil concentration level (40 mg L⁻¹, 10 min) than TMS (60 mg L⁻¹, 10 min), but the recovery period of clove oil, was significantly longer. Clove oil was the most effective in reducing the short-term stress induced by routine biometry (20 mg L⁻¹, 10 min) and also by transporting (1 mg L⁻¹, 8 h). Whereas, for long-term exposure, 40 mg L⁻¹ TMS was found to be safe.     

Bioencapsulation of erythromycin using adult brine shrimp, Artemia franciscana (Latreille)

Live adult brine shrimp, Artemia franciscana (Latreille), were enriched with erythromycin to determine if Artemia could accumulate therapeutic levels for subsequent feeding to young fish. Three trials were conducted to determine the erythromycin incorporation and survival rates of enriched Artemia when fed either liposomes containing erythromycin or various erythromycin suspensions. Erythromycin concentration in Artemia fed a liposome suspension was low (∼ 5 μg mL⁻¹) relative to Artemia fed the direct suspension (> 100 μg mL⁻¹) over the same time period. When enriched with suspensions up to 1 g erythromycin L⁻¹ sea water for 14 h, Artemia survival was not significantly affected ( P > 0.05) relative to controls. Using a suspension of 1 g L⁻¹, tissue erythromycin concentrations of 109 ± 16 μg erythromycin mL⁻¹  Artemia homogenate (mean ± SEM) were achieved after 12 h. Concentrations above 170 μg mL⁻¹ were obtained using suspensions of 2–5 g L⁻¹, but Artemia survival significantly ( P < 0.05) decreased.     

Demersal fish and invertebrate biomass in relation to an offshore hypoxic zone along the US West Coast

In August 2007, as part of the NOAA National Marine Fisheries Service (NMFS) West Coast Groundfish Bottom Trawl Survey, we examined the biomass of demersal organisms in a known hypoxic area off the Oregon coast. Although observed each summer, the intensity of hypoxia has varied annually (2002–2007) with the greatest temporal and spatial extent noted in 2006. In 2007 we identified the geographic extent of the hypoxic zone and sampled 17 stations along two depth contours (50 and 70 m) within the area. A Sea-Bird SBE 19 plus equipped with a dissolved oxygen (DO) sensor was attached to the bottom trawl to monitor oxygen concentration during each tow. Bottom DO concentrations at all stations were hypoxic with means along the tow tracts ranging from 0.43 to 1.27 mL L⁻¹. Total catch per unit effort (ln CPUE, kg hectare⁻¹) and species diversity (number of species, N ) were significantly and positively related to oxygen concentration along the hypoxic gradient. In addition, CPUE (natural log-transformed) for eight fish species and five benthic invertebrate species were significantly and positively related to bottom oxygen concentration within the hypoxic region. Condition factors for five fish species, as well as Dungeness crab ( Cancer magister ) increased with increased bottom oxygen levels along the hypoxic gradient. Historical catch (2003–2006) within the hypoxic zone indicates that biomass was significantly lower in 2006, the year with the lowest bottom DO levels, relative to other years.     

Spatial differentiation in the eastern Pacific yellowfin tuna revealed by microsatellite variation

ABSTRACT:   Five eastern Pacific yellowfin tuna samples (four northern: 10–25°N, 95–130°W, and one southern: 16–18°S, 95–97°W), collected from fishing vessels between 1994 and 2002 were analyzed for variation at seven microsatellite loci to evaluate their spatial genetic homogeneity. Single-locus homogeneity exact tests revealed significant genetic differentiation caused by three of seven loci. Pairwise sample comparisons of multilocus allele-frequency homogeneity tests and subpopulation division ( F _ST), revealed significant differentiation in comparisons between north equatorial samples and the south equatorial sample. amova analysis among collections grouped as northern and southern populations separated by the equator in the eastern Pacific confirmed the differentiation observed. These results may be considered as preliminary evidence of the presence of discrete populations in the eastern Pacific yellowfin tuna. The possibility that the spatial differentiation observed corresponds to temporal variation or non-random sampling cannot be discarded. The genetic differences encountered need to be corroborated by increasing sample sizes, including temporal replicates, and by the use of an alternative marker.     

Continuous exposure to infectious pancreatic necrosis virus during early life stages of rainbow trout, Oncorhynchus mykiss (Walbaum)

Rainbow trout, Oncorhynchus mykiss (Walbaum), were exposed continuously to infectious pancreatic necrosis virus (IPNV) at 0, 10¹, 10³ or 10⁵ plaque forming units (pfu) L⁻¹ of water to estimate the effects of chronic IPNV exposure on early life stages. Fish density averaged 35 fish L⁻¹ (low density) or 140 fish L⁻¹ (high density), and the tank flow rate was 250 mL⁻¹ min. Virus exposure began at 6 days before hatch and continued until fish were 44 days old. Cumulative per cent mortality, analysis of survival and hazard functions, and discrete-time event analysis were used to explore the patterns of survival and mortality. In eggs and fish exposed to IPNV, mortality significantly greater than in the 0 pfu L⁻¹ exposure did not occur until IPNV concentration was 10⁵ pfu L⁻¹ at low fish density and 10³ pfu IPNV L⁻¹ at high fish density. These results suggest that in the natural aquatic environment, where rainbow trout densities are likely to be considerably lower than in this study, mortality resulting from infection with IPNV will very likely not occur when ambient concentrations of virus are ≤10³ pfu IPNV L⁻¹. In aquaculture rearing units, trout density is likely to be as high or higher than the densities used in this study. Therefore, continuous inputs of virus at concentrations greater than 10¹ pfu L⁻¹ may result in IPN epidemics in aquaculture facilities.     

Effects of a peroxide-based commercial product on bacterial load of larval rearing water and on larval survival of two species of Sparidae under intensive culture: preliminary study

Larvae of two Mediterranean Sparidae species, Sparus aurata and Dentex dentex , were used to test the efficacy of a peroxide-based product (Ox-Aquaculture^©) on the reduction in bacterial load in larval rearing water and its effects on larval survival. Eleven-day-old S. aurata larvae and 15-day-old D. dentex larvae were exposed to different concentrations of Ox-Aquaculture^© (50, 100 and 200 mg L⁻¹, and 20 and 50 mg L⁻¹ respectively) for 1 h. Results indicated that 50 and 20 mg L⁻¹ were the most effective concentrations for the reduction in bacterial load (at least one order of magnitude) after 1 h treatment, without affecting larval survival and/or vitality in 11 dph S. aurata and 15 dph D. dentex larvae respectively. Ox-Aquaculture^© concentrations of 200 and 50 mg L⁻¹ during 1 h affected negatively final survival rate of the larvae of S. aurata and D. dentex respectively.     

Olfactory nerve response of masu salmon (Oncorhynchus masou Brevoort) and rainbow trout (O. mykiss Walbaum) to clove oil and MS-222

Two anaesthetics, clove oil and methane sulphonate (MS-222), were examined for their effects on the olfactory nerve response of masu salmon ( Oncorhynchus masou Brevoort) and rainbow trout ( O. mykiss Walbaum). Exposing both species to clove oil for 3 min at concentrations of 50 and 100 mg L⁻¹, or for 10 min at 50 mg L⁻¹, did not significantly reduce their olfactory response. Directly applying clove oil anaesthesia to the olfactory epithelium significantly reduced olfactory response though after 20 min, olfactory response recovered to 70% and 52% of pre-treatment levels in masu salmon and rainbow trout respectively. Compared with the post-anaesthetic recovery of responses after clove oil (50 mg L⁻¹), buffered MS-222 (100 mg L⁻¹) with NaHCO₃ (100 mg L⁻¹), and unbuffered MS-222 (100 mg L⁻¹) treatment for 3 min, the response after MS-222 treatment declined gradually and significantly, but not after clove oil and MS-222+NaHCO₃ treatments. Clove oil appears to be an effective and relatively safe anaesthetic for salmonids with little long-term impact on their olfactory response, which plays a crucial role in their life history.     

热带印度洋大眼金枪鱼渔场时空分布与温跃层关系

为了解印度洋大眼金枪鱼(Thunnus obesus)温跃层参数适宜分布区间及季节变化,采用Argo浮标剖面温度数据重构热带印度洋各月平均温跃层特征参数,并结合印度洋金枪鱼委员会(IOTC)大眼金枪鱼延绳钓渔业数据,本文绘制了月平均温跃层特征参数和月平均CPUE的空间叠加图,用于分析热带印度洋大眼金枪鱼渔场CPUE时空分布和温跃层特征参数的关系。结果表明,热带印度洋温跃层上界深度、温度和下界深度都具有明显的季节性变化,大眼金枪鱼中心渔场分布和温跃层季节性变化有关。夏季季风期间,高CPUE渔区温跃层上界深度在30~50 m,浅于冬季的50~70 m;温跃层上界温度范围为24~30℃。在冬季季风期间,高CPUE区域对应的温跃层上界温度范围为27~30℃;从马达加斯加岛北部沿非洲大陆至索马里附近海域,温跃层下界深度在170~200 m时的渔区CPUE普遍较高;当深度超过300 m时,CPUE值均非常低。采用频次分析和经验累积分布函数计算其最适温跃层特征参数分布,得出大眼金枪鱼最适温跃层的上界、下界温度范围分别是26~29℃和13~15℃;其上界、下界深度范围分别是30~60 m和140~170 m。文章初步得出印度洋大眼金枪鱼中心渔场温跃层各特征参数的适宜分布区间及季节变化特征,为金枪鱼实际生产作业和资源管理提供理论参考。     

印度洋中南部水域金枪鱼延绳钓钓钩钩型对钓获对象的选择性

基于2008年9月至2009年4月在印度洋中南部水域金枪鱼延绳钓渔场收集的数据,研究分析和比较了3种钓钩钩型(传统金枪鱼钩、“J”形钩和圆形钩)的渔获效益及对钓捕对象的选择性。结果表明:(1) 从渔获种类上看,大眼金枪鱼和大青鲨金枪鱼钩钓获比例最高,“J”形钩和圆形钩的钓获比例相当;而长鳍金枪鱼则为金枪鱼钩钓获比例最高,其次为“J”形钩和圆形钩。(2) 大眼金枪鱼存活率以金枪鱼钩最高,“J”形钩最低;长鳍金枪鱼则为“J”形钩稍高于圆形钩,金枪鱼钩最低;大青鲨则以圆形钩最高,“J”形钩最低。(3) “J”形钩钓获的长鳍金枪鱼和鲨鱼平均叉长较金枪鱼钩和圆形钩稍大;而金枪鱼钩钓获的大眼金枪鱼平均叉长较圆形钩和“J”形钩稍大。(4) 3种钩型钓获的长鳍金枪鱼、大眼金枪鱼和大青鲨叉长分布均不存在显著性差异。     

Separation of the Taiwanese regular and deep tuna longliners in the Indian Ocean using bigeye tuna catch ratios

ABSTRACT:   Taiwanese longline (LL) fisheries operating in the Indian Ocean usually target albacore tuna (ALB), swordfish (SWO) and yellowfin tuna (YFT) using regular LL. Bigeye tuna (BET), however, is targeted using deep LL. Thus, these two types of LL are considered to be different gears as they target different tuna species. Regular or deep LL fishing is defined by number of hooks per basket (NHB): regular LL if 6 ≤ NHB ≤ 10 and deep LL if 11 ≤ NHB ≤ 20. However, NHB information was available in only some of the recent LL data (1995–1999). This situation had caused problems of biased results in stock analysis in the past. Thus, the objective of our study was to explore an effective method to separate the two types of LL fishing by considering species composition. Some intervals of BET catch ratios were found to be effective in separating the regular and deep LL catches, i.e. 0.0 ≤ BET/(BET + ALB + SWO) ≤ 0.4 and 0.8 ≤ BET/(BET + ALB) ≤ 1.0, respectively. Using these two separators, the LL known data set (1995–1999) (learning data set) was classified. Correct classification occurred in 67.7% of the data, while 23.1% of the data were unclassified (11.9% due to zero catches and 11.2% due to classification into both LL types), and 9.2% were misclassifications. Then, using the methods developed, the LL unknown data set in the historical data (1979–1999) was classified and nominal CPUE values were calculated for four species. The CPUE trends based on this study were likely to be more reliable than those of previous studies.     

Behaviour of immature yellowtails (Seriola quinqueradiata) observed by electronic data-recording tags

The long-term behaviour of immature yellowtails, Seriola quinqueradiata , was studied using electronic data-recording tags in Sagami Bay, Japan, during the autumn and early winter. Temperature or depth data were continuously recorded for 5–69 days on six yellowtails. The temperature recorded from the 0-year-old yellowtails showed only small variations (<0.5°C day⁻¹) around the SST on the coast, indicating the 0-years stayed in the immediate coastal area with little horizontal movement. The 1-year-old yellowtail showed larger temperature variations that reached 3°C day⁻¹, which implies distinctly larger horizontal movements than the 0-year-olds. Depth records showed the 0-years stayed around 10 m while the 1-year yellowtail swam in deeper water (mainly 10–30 m) with large variations. The latter often dived to 40 m in the daytime, but shallower than the depth of the thermocline. Both temperature and depth records showed apparent diurnal patterns. Comparing the fish data with environmental conditions, it is suggested that 1-year yellowtails stay close to the coast during the night, move at dawn to feed in the daytime and return at dusk via a frontal zone. In addition, wind stress could change yellowtails' behaviour.     

Feasibility of cultivation of Kappaphycus alvarezii (Doty) Doty at different localities on the Northwest coast of India

Kappaphycus alvarezii was cultivated at three places, viz. Mithapur, Okha and Beyt Dwarka on the Northwest coast of India. The biomass and growth rates were measured at 15-day intervals up to 45 days and varied differently for different growth periods at these places. Thus, at 15, 30 and 45 days, the biomass (fresh wt) varied from 182.0±19.96 to 435.0±23.66 g, from 366.0±118.09 to 1096.0±61.43 g and from 530.5±50.95 to 1537.0±43.54 g, respectively, with respective daily growth rates (%) from 3.95±0.78 to 9.80±0.63, from 3.64±0.01 to 13.98±3.07 and from 3.69±0.23 to 6.07±0.06. The seawater temperature, salinity, nitrate and phosphate ranged from 19.3 to 26.9 °C, from 30.81 to 36.83‰, from 11.60 to 19.75 μmol L⁻¹ and from 2.37 to 5.0 μmol L⁻¹ respectively. The growth rate between the culture months was significantly different at Okha at P <0.01. Further, it was significantly correlated to salinity at Mithapur while at Okha and Beyt Dwarka, the same was significantly correlated to nitrate and seawater temperature. Based on this study, commercial cultivation at these localities is quite feasible.