胶州湾底栖生态系统健康评价——基于大型底栖动物生态学特征

根据2017年7月山东省胶州湾海域的大型底栖动物调查数据，应用聚类分析、生物多样性和Multivariate-AZTI’s Marine Biotic Index (M-AMBI)等方法分析了大型底栖动物的生态学特征，评估了胶州湾底栖生态系统的健康状况。结果显示，调查海域共采集到大型底栖动物64种，其中，多毛类25种，甲壳动物23种，软体动物9种，棘皮动物和其他类群共7种。该海域大型底栖动物生物量和丰度的平均值分别为70.0 g/m2和132 ind./m2，菲律宾蛤仔(Ruditapes philippinarum)、寡鳃齿吻沙蚕(Nephthys oligobranchia)和纽虫(Nemertinea)是优势种。物种多样性指数( )为0.69~3.77，平均值为2.35，丰富度指数(d)为0.67~3.12，平均值为1.56，Pielou均匀度指数(J)为0.25~1.00，平均值为0.81。多样性AMBI指数(M-AMBI)为0.26~0.60，平均值为0.44。根据CLUSTER分析结果，在15%相似水平上可将研究站位划分为3个群落，菲律宾蛤仔养殖密度较大的站位群落结构较为相似，被划分在同一个群落中，聚类结果与菲律宾蛤仔养殖密切相关。大型底栖动物群落的多样性指数和M-AMBI指数分析显示，胶州湾海域底栖生态系统受到中等程度的干扰。     

江苏启东近岸海域大型底栖动物群落健康评价

海洋大型底栖动物能对自然和人为活动导致的水和沉积物质量变化做出可预测的响应,因此利用底栖生物作为海洋生态环境监测的生物指标和进行系统健康度量的生物指数已经得到了广泛的认可。AMBI指数(AZTI’s Marine Biotic Index)法、ABC(abundance/biomass comparison)曲线法和BENTIX指数法可以有效地评价河口和近岸海域大型底栖动物群落对人为和自然扰动的响应。在2013年1、6、8、11月分别对启东近岸海域的大型底栖生物进行了调查,对比分析了4个季节大型底栖生物种类数、优势种、密度和生物量的差异,并运用ABC曲线法、AMBI和BENTIX指数法评估了调查海域大型底栖动物群落的受干扰状况。结果表明,该海域共采集大型底栖动物86种,其中优势类群为多毛类。群落中的优势种类主要为钩虾(Gammarus sp.)。调查海域年平均总生物量和丰度分别为6.92g·m-2和84.33 ind·m-2,且存在季节性差异。根据ABC法、AMBI法和BENTIX指数法分析显示绝大部分区域受到轻微程度人为的干扰,特别是夏季受到干扰程度较为强烈。研究结果表明,启东近岸受一定程度人类活动影响。     

珠江口大型底栖动物数量与生物多样性的分布特征

为了更好地了解河口生物多样性的演变规律及退化机制,根据2015年1—12月珠江口大型底栖动物调查资料对珠江口大型底栖动物现存量和生物多样性的分布特征进行了研究。结果表明,11次采样(受台风影响7月珠江口未采集到大型底栖动物)共获取大型底栖动物67种,其中环节动物多毛纲27种,节肢动物24种,软体动物12种,其它类群4种,主要是底栖鱼类、刺胞动物和纽形动物。2015年珠江口各站位大型底栖动物丰度的变化范围在8～1 192个·m~(-2)之间,珠江口大型底栖动物丰度的高值出现在6月和9月的崖门(分别为1 192个·m~(-2)和1 048个·m~(-2))以及9月的虎跳门(1 048个·m~(-2)),日本大螯蜚(Grandidierella japonica)、中华拟亮钩虾(Paraphotis sinensis)、凸壳肌蛤(Musculus senhousei)和彩虹明樱蛤(Moerella iribescens)丰度较高。大型底栖动物生物量变化范围在0. 02～42. 50 g·m~(-2)之间,生物量的高值出现在9月的崖门、5月的鸡啼门、2—3月的磨刀门及4月的蕉门,上述站位的生物量均大于30. 00 g·m~(-2),缢蛏(Sinonovacula constricta)、光滑河篮蛤(Potamocorbula laevis)、黑龙江河篮蛤(P. amurensis)、凸壳肌蛤和日本大螯蜚生物量较高。珠江口大型底栖动物香浓威纳指数高值出现在3月鸡啼门,为2. 46;低值出现在10月磨刀门,为0. 21。香浓威纳指数均值在1. 11～1. 81之间。鸡啼门和虎跳门大型底栖动物香浓威纳指数值月际变化较稳定。运用ABC曲线对珠江口大型底栖动物扰动状况进行评价,结果表明,1月珠江口大型底栖动物受到中等程度扰动,2—4月大型底栖动物群落有受到中等程度干扰的趋势。     

江苏中南部潮间带大型底栖动物时空分布特征

2013年5月(春季)、8月(夏季)、11月(秋季),对江苏中南部潮间带大型底栖动物进行了定性和定量调查。共采集到大型底栖动物68种,定量63种,定性19种,多毛类、软体动物以及甲壳动物是组成大型底栖动物的主要类群。优势种为文蛤(Meretrix meretrix)、泥螺(Bullacta exarata)、四角蛤蜊(Mactra veneriformis)、托氏虫昌螺(Umbonium thomasi)、加州齿吻沙蚕(Nephtys californiensis)、双齿围沙蚕(Nereis aibuhitensis)以及宽身大眼蟹(Macrophthalumus dilatatus)等。年平均总生物密度65.15 ind·m-2,平均总生物量94.21g·m-2。和历史资料比较后发现,自20世纪80年代至今,江苏中南部潮间带大型底栖动物生物量有增无减。大型底栖动物的生物密度、生物量、多样性和相对重要性指数随季节的不同而有所变化,其中生物密度、生物量以及多样性指数均以春季最高。江苏中南部潮间带大型底栖动物群落生物量优势度曲线位于丰度曲线上方,群落结构稳定性较高,未出现明显扰动。     

小麦岛邻近海域秋季大型底栖动物生态特征

为探明小麦岛邻近海域大型底栖动物生态特征,于2018年10月对小麦岛邻近海域大型底栖动物群落进行调查和分析,通过野外采样、室内生物鉴定和环境因子测定,对其多样性、群落结构、环境因子相关性和丰度—生物量比较曲线进行研究.调查结果显示,本次调查共鉴定出大型底栖动物80种,包括环节动物多毛类57种、节肢动物甲壳类15种、软体...     

辽东湾海域大型底栖动物群落特征

根据2007年的4月(春季)和10月(秋季)辽东湾海域19个调查站位所采集的底栖生物样品的鉴定结果,分析了其种类组成、丰度、生物量、生物多样性及群落结构特征,探讨了大型底栖动物群落特征分布与环境因子的相关性。调查共发现大型底栖动物46种,其中春季33种,秋季26种;多样性指数(H')分布无显著空间差异,丰富度指数(dMa)和均匀度指数(J)分布趋势较为一致,高值区集中分布于辽东湾中部,低值区位于辽东湾西北部沿岸水域;群落聚类分析将春秋两季均划分为5组,但5组内容不同,表明季间群落结构变化较大;群落结构与环境因子的相关分析和BIOENV分析表明生物与环境因子之间无显著相关。     

大亚湾海域大型底栖生物种类组成及特征种

利用2008年4个航次在南海北部大亚湾海域开展的124个站次海洋生物调查资料,对大型底栖动物种类组成、优势种和特征种进行研究,结果表明:(1)大亚湾大型底栖动物群落季变化显著、种类更替明显.2008年共采获大型底栖动物104科279种（类）,各季种类平均更替率高达63％.(2)优势种组成较为稳定,单一种的优势地位显著.粗帝汶蛤(Timoclea scabra)为大亚湾大型底栖动物第一优势种,周年均保持极高的优势地位.除粗帝汶蛤外还有毛头梨体星虫(Apionsoma trichocephala)、脑纽虫(Cerebratulina sp.)、独毛虫(Tharyx sp.)和中蚓虫(Mediomastus sp.)为大亚湾周年优势种,优势种组成较为稳定.(3)大亚湾大型底栖动物以多毛类为特征种类.多毛类在大亚湾海域大型底栖动物群落中具有重要作用,其代表和反映了整个群落的特征.(4)大型底栖动物种类组成情况反了大亚湾海域环境状况.大亚湾大型底栖动物种类组成更替明显、特征种节变化大,反映出大亚湾海域环境季节变化明显,尤其是春、夏和秋3季,秋、冬季较为稳定.优势种组成的年际变化表明,大亚湾海域生态环境发生了较大程度的变化.此外,多毛类在底栖动物群落中地位的突显,也反映出大亚湾海域营养水平的变化.对比历史资料分析,结论认为,大亚湾大型底栖生物种类数远低于历史水平,群落简单趋势仍较为明显.虽然因采样区域和样品分选工具的差异,2008年种类远多于2004年调查结果,但仍低于1987年的473种.此外,1987年底栖动物的站均出现种数为50.6种/站,最高可达100种/站.2008年站均出现种数为15.0种/站,最高种数为38种/站,依然远低于历史水平.本研究旨在为系统开展大亚湾受损生态系统的恢复提供更为全面、丰富、准确的基础资料.     

长江口九段沙潮间带大型底栖动物季节分布特征的初步研究

2005年4月(春季)、7月(夏季)、10月(秋季)和2006年1月(冬季).对长江口九段沙潮间带大型底栖动物进行了定性和定量调查.共采集到大型底栖动物73种,平均丰度442.94 ind·m-2,生物量40.78 g·m-2.与历史资料比对,大型底栖动物的种数显著增加,新记录31种,曾经有过报道但未采集到标本的有3种;大型底栖动物的丰度变化不大,生物量有明显增加,多样性指数增大.大型底栖动物的丰度、生物量、多样性指数和相对重要性指数随季节的不同而有所变化,其中丰度和生物量以秋季最高,夏季次之,春季和冬季较低;多样性指数冬季最高,夏季次之,春季和秋季较低.优势种为谭氏泥蟹、梨形环棱螺、绯拟沼螺、琵琶拟沼螺、河蚬、焦河篮蛤、中国绿螂和丝异蚓虫;相对重要性指数值较高的有无齿相手蟹、天津厚蟹、谭氏泥蟹、中华拟蟹守螺、堇拟沼螺、绯拟沼螺、琵琶拟沼螺、梨形环棱螺、中国绿螂、焦河篮蛤、河蚬和丝异蚓虫.大型底栖动物的分布主要受水温、水文和工程的影响,此外,工程建设和互花米草扩散对其也造成了一定的影响.     

胶州湾冬季大型底栖动物群落结构及其与环境因子的相关性

为了解胶州湾大型底栖动物群落的动态变化以及与环境因子的关系,本研究通过2016年冬季在胶州湾12个站位采集到的大型底栖动物样品,共鉴定出大型底栖动物66种,其中环节动物32种,节肢动物、软体动物和棘皮动物分别为17种、9种和3种,脊索动物2种,纽形动物、头索动物、半索动物各1种。优势种为寡鳃齿吻沙蚕(Nephtys oligobranchia)、丝异须虫(Heteromastus filiformis)、青岛文昌鱼(Brachiostoma belcheri tsingtauense),优势度分别为0.02、0.147和0.024。大型底栖动物的总平均栖息密度为176.7 ind/m~2,总平均生物量为159.5 g/m~2。水平分布显示,栖息密度由高到低依次为湾内近岸海域、湾外海域、湾内离岸海域,生物量水平分布湾外海域湾内海域。多样性指数(H')取值为1.19~3.54,平均值为2.65;丰富度指数(d)取值为0.91~2.29,平均值为1.47;均匀度指数(J′)取值为0.46~1.00,平均值为0.87。根据Cluster结果,可将调查站位划分为4个群落。ABC曲线显示,群落Ⅰ受到严重的扰动(H'=1.65),群落Ⅱ(H'=2.84)和群落Ⅲ海域(H'=2.32)有轻微的扰动,群落Ⅳ未受干扰(H'=3.54)。BIOENV分析表明,与群落结构关系最密切的环境因子为水深、溶解有机碳(DOC)、中值粒径和Zn含量(r=0.524)。胶州湾受人类活动干扰较多,大型底栖动物群落结构不稳定,需进行长期监测和评价。     

江门近岸海域大型底栖动物群落结构的分布特征

根据2016年江门近岸海域4个航次的调查数据,对其大型底栖动物现存量和多样性分布特征进行了研究。调查共鉴定出大型底栖动物56种,其中软体动物21种,环节动物18种,节肢动物7种,棘皮动物3种,纽形动物和腔肠动物各2种,星虫动物、脊索动物和螠虫各1种。江门近岸海域各站位大型底栖动物栖息密度和生物量分别介于10～920个·m~(-2)和0.2～267.7 g·m~(-2),栖息密度总体呈现湾外大于湾内的趋势;群落中以膜质伪才女虫(Pseudopolydora kempi)和中华内卷齿蚕(Aglaophamus sinersis)分布最广泛,其中中华内卷齿蚕为四季共同优势种。ABC曲线分析表明,该海域群落整体的稳定性一般,春、秋季大型底栖动物群落受到一定程度的干扰,稳定性较弱。相关性分析表明,水深、盐度、温度、磷酸盐、沉积物类型、捕食压力是影响群落结构时空差异的主要因素。     

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.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

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.