不同溶解氧条件下亚硝酸盐和非离子氨对大菱鲆的急性毒性效应

研究了过饱和氧条件下亚硝酸盐和氨氮对大菱鲆急性毒性效应,同时对比了在正常溶解氧条件下亚硝酸盐和氨氮对大菱鲆急性毒性效应。实验结果表明,过饱和氧条件下亚硝酸盐对大菱鲆的48hLC50值和96hLC50值(95%可信限)分别为467.60mg/L和390.78mg/L,非离子氨对大菱鲆的48hLC50值和96hLC50值(95%可信限)分别为2.40mg/L和1.73mg/L;而正常溶氧条件下,亚硝酸盐对大菱鲆的48hLC50值和96hLC50值(95%可信限)分别为181.07mg/L和130.66mg/L,非离子氨对大菱鲆的48hLC50值和96hLC50值(95%可信限)分别为1.82mg/L和1.14mg/L。亚硝酸盐和非离子氨对大菱鲆均具有一定的毒性,其主要中毒症状表现为,中毒的个体开始急躁不安并沿槽壁狂游,频繁发生相互碰撞或与槽壁摩擦,随后行动减缓并伴有侧游或侧翻动作,呼吸速度减慢,发生昏迷并沉落水底,直至死亡。死亡的大菱鲆鱼体弯曲,体色变淡,鳃盖张开。无论在过饱和氧还是在正常溶氧条件下非离子氨对大菱鲆的毒性都远大于亚硝酸盐的毒性,同时高浓度溶解氧的存在使大菱鲆对这两种毒物的耐受能力得以提高。提出了在大菱鲆循环水养殖过程中可以通过向水体充氧的方式以提高大菱鲆对亚硝酸盐和非离子氨的耐受力。     

不同溶氧条件下亚硝酸盐和氨氮对半滑舌鳎的急性毒性效应

研究了正常溶解氧(5.5～6.0mg/L)和过饱和氧(10～12mg/L)条件下亚硝酸盐和氨氮对半滑舌鳎急性毒性效应。实验结果表明,正常溶氧条件下,亚硝酸盐对半滑舌鳎的48hLC50值和96hLC50值(95%可信限)分别为48.2mg/L(43.56～53.34mg/L)和41.66mg/L(37.03～46.86mg/L),非离子氨对半滑舌鳎的48hLC50值和96hLC50值(95%可信限)分别为0.76mg/L(0.64～0.89mg/L)和0.58mg/L(0.48～0.70mg/L);而过饱和氧条件下亚硝酸盐对半滑舌鳎的48hLC50值和96hLC50值(95%可信限)分别为120.68(110.82～131.42mg/L)和103.53mg/L(94.83～113.03mg/L);非离子氨对半滑舌鳎的48hLC50值和96hLC50值(95%可信限)分别为2.53mg/L(2.42～2.66mg/L)和2.39mg/L(2.31～2.49mg/L)。最后,提出了在半滑舌鳎养殖过程中可以通过向水体充氧的方式以提高半滑舌鳎对亚硝酸盐和非离子氨的耐受力。     

不同溶氧水平下氨氮和亚硝酸盐对黄颡鱼的急性毒性研究

在高溶氧(10.77±0.40)mg/L、中溶氧(6.89±0.33)mg/L和低溶氧(3.45±0.54)mg/L水平下,研究了氨氮和亚硝酸盐对黄颡鱼急性毒性效应。结果显示:高溶氧水平下,氨氮和亚硝酸盐对黄颡鱼的96 h-LC50值(95%可信区间)分别为148.1 mg/L(125.03～172.37 mg/L)、206.52 mg/L(164.25～246.23 mg/L);在中等溶氧水平下,氨氮和亚硝酸盐对黄颡鱼的96 h-LC50值(95%可信区间)分别为106.69 mg/L(89.92～123.70 mg/L)、145.77 mg/L(116.77～174.77 mg/L);而低溶氧水平下,氨氮和亚硝酸盐对黄颡鱼的96 h-LC50值(95%可信区间)分别为68.03 mg/L(58.32～77.89 mg/L)、81.33 mg/L(64.76～96.70 mg/L)。结果表明,在3种溶氧条件下,氨氮对黄颡鱼的毒性明显大于亚硝酸盐对黄颡鱼的毒性,因而氨氮对黄颡鱼的毒性成为其养殖过程中的重要影响因子。     

氨氮和亚硝酸盐对龙虎斑的急性毒性研究

为研究工厂化养殖条件下氨氮、亚硝酸盐对龙虎斑的急性毒性效应,采用常规生物急性毒性试验法,进行了氨氮和亚硝酸盐对龙虎斑幼鱼[体质量(59.37±7.11)g,体长约10 cm]的急性毒性试验。结果表明,在水温为(28.57±1.61)℃,pH为(7.7±0.1),盐度为(28±1),溶解氧为(5.5±1.0)mg/L的条件下,氨氮对龙虎斑的24、48、72、96 h半致死浓度(LC_(50))分别为43.15、40.16、37.71、33.43 mg/L,安全浓度(SC)为3.343 mg/L;对应的非离子氨LC50分别为1.599、1.488、1.397、1.239 mg/L,SC为0.1239 mg/L;亚硝酸盐对龙虎斑的24、48、72、96 h LC_(50)分别为306.72、227.09、131.40、90.41 mg/L,SC为9.041 mg/L。氨氮和亚硝酸盐对龙虎斑的毒性随药物浓度的升高和暴露时间的延长而增强,对鱼体的LC50均随暴露时间的延长呈下降趋势。     

夹竹桃提取物对鲤科鱼类的毒性试验

采用静水式试验方法,在水温为20±1℃的条件下,研究夹竹桃提取物对鲤鱼、鳊鱼和白鲢的毒性效应,以期为该药物在渔病防治中的使用提供用药的参考依据。试验结果表明,夹竹桃提取物对鲤鱼的24 h LC_(50)、48 h LC_(50)、96 h LC_(50)分别为149．55 mg/L、78．76 mg/L、66．09 mg/L;安全浓度为6．61 mg/L。对鳊鱼的24 h LC_(50)、48 h LC_(50)、96 h LC_(50)分别为269．41 mg/L、94．54 mg/L、40．63 mg/L;安全浓度为4．06 mg/L。对白鲢的24 h LC~(50)、48 h LC~(50)、96 h LC~(50)分别为91．37 mg/L、69．09 mg/L、48．71 mg/L,安全浓度为4．87 mg/L。     

3种工业废水对中国对虾幼体及仔虾的急性毒性效应

通过室内毒理实验,研究印染废水(主要有毒物质为苯胺C6H5NH2和苯酚C6H5OH,质量浓度分别为20 mg/L和24 mg/L)、电镀废水(主要有毒物质为锌、铜和铅,质量浓度分别为1 970 mg/L、9 mg/L和7.5 mg/L)、农药废水(主要有毒物质为久效磷和亚磷酸盐二甲酯)及其混合废水对中国对虾(Peanaeus chinensis)无节幼体和仔虾的急性毒性作用.结果表明,印染废水、电镀废水、农药废水及其混合物对无节幼体48 h LC50(95%可信限区间)和96 h LC50(95%可信限区间)分别为2.27%(1.72%～2.99%)、0.29%(0.22%～0.37%)、0.86%(0.64%～1.15%)及0.30%(0.22%～0.40%)和1.03%(0.79%～1.34%)、0.16%(0.12%～0.19%)、0.38%(0.30%～0.48%)及0.18%(0.13%～0.24%);对仔虾48h LC50(95%可信限区间)和96 h LC50(95%可信限区间)分别为3.51%(2.38%～5.18%)、0.40%(0.29%～0.55%)、2.06%(1.34%～3.17%)及0.52%(0.39%～0.71%)和1.44%(1.06%～1.96%)、0.21%(0.15%～0.29%)、0.71%(0.51%～0.99%)及0.22%(0.17%～0.29%).3种工业废水的毒性从大到小依次为:电镀废水、农药废水、印染废水,无节幼体较仔虾对这废水的毒性更为敏感.3种废水以等体积混合时,对无节幼体和仔虾的联合毒性表现为协同作用.     

消油剂对海湾扇贝(Argopecten irradians)的急性毒性效应

本研究以海湾扇贝(Argopecten irradians)为研究对象,通过96 h半静水毒性实验,探讨了消油剂、0号柴油分散液(WAF)与0号柴油乳化液(CEWAF)对海湾扇贝24 h、48 h、72 h、96 h急性毒性效应。结果显示,消油剂对海湾扇贝的24 h、48 h、72 h和96 h半致死浓度(95%可信限)分别为1905(1570-2451 mg/L)、1293(1070-1556 mg/L)、1015(721-1348 mg/L)、846 mg/L(660-1020 mg/L);WAF对海湾扇贝的24 h、48 h、72 h和96 h半致死浓度(95%可信限)分别为36.57(29.42-48.96 mg/L)、23.10(21.07-25.39 mg/L)、14.99(13.66-16.41 mg/L)、11.31 mg/L(8.37-14.47 mg/L);CEWAF对海湾扇贝的24 h、48 h、72 h和96 h半致死浓度(95%可信限)分别为12.71(10.78-15.55 mg/L)、8.51(7.99-9.07 mg/L)、6.56(4.46-7.74 mg/L)、5.42 mg/L(4.51-6.29 mg/L)。消油剂、0号柴油分散液、0号柴油乳化液对海湾扇贝96 h安全浓度分别为84.6、1.13、0.54 mg/L。随着实验时间的延长,消油剂、WAF和CEWAF对海湾扇贝的半致死浓度(LC_(50))均呈逐渐降低之势,半致死浓度与时间呈幂函数关系,其关系式分别为y=12242x~(–0.583)、y=564.37x~(–0.848)、y=89.987x~(–0.613)。在受试溶液中暴露相同时间,海湾扇贝的半致死浓度从高到低依次为消油剂、WAF和CEWAF,说明CEWAF对海湾扇贝的毒性大于消油剂和WAF,这对于在养殖海区使用消油剂处理溢油事故具有重要的指导意义。     

氨氮和亚硝酸盐对单环刺螠幼体的急性毒性实验

在水温15.1～17.3℃,pH 7.88～8.15,盐度32.17‰～32.28‰,溶解氧6.40～7.40 mg/L的条件下,采用半静水法研究了氨氮和亚硝酸盐对体质量(2.86±0.43)g的单环刺螠(Urechis unicinctus)幼体的急性毒性效应。试验结果表明,单环刺螠幼体中毒后体色变暗,对外界刺激变得不敏感,最后身体缩成一团或细线状。随着氨氮和亚硝酸盐质量浓度升高死亡率逐渐升高,存在明显的剂量效应和时间效应。氨氮对单环刺螠幼体96 h半致死质量浓度分别为620.79 mg/L(95%置信区间557.62～691.11 mg/L),安全质量浓度为62.08 mg/L,对应非离子氨浓度为13.85 mg/L(95%置信区间12.44～15.42 mg/L),安全质量浓度为1.39 mg/L;亚硝酸盐对单环刺螠幼体96 h半致死质量浓度为243.90 mg/L(95%置信区间223.10～266.65 mg/L),安全质量浓度为24.39 mg/L。非离子氨对单环刺螠幼体毒性大于亚硝酸盐毒性。     

亚硝酸盐氮对日本囊对虾幼虾的急性毒性研究

在水温(28±0.2)℃、盐度29.8±0.2、pH 8.0±0.2和溶氧6.0 mg/L的条件下,将体长(49.28±4.79)mm日本囊对虾(Marsupenaeus japonicus)幼虾放在盛水20 L的100 L白桶中,用NaNO_2(分析纯)溶于新鲜海水配制成2 000 mg/L的母液,使试验组水中亚硝酸盐氮(NO_2~--N)质量浓度为151.36、239.88、380.19、602.56、954.99 mg/L,采用静水毒性试验法研究了亚硝酸盐氮对日本囊对虾幼虾的急性毒性。结果显示,NO_2~--N毒性效应与质量浓度和胁迫时间呈正相关。在同一时间下日本囊对虾的死亡率随着NO_2~--N质量浓度的升高而增加;在同一质量浓度下对虾的死亡率随着时间的延长而升高。NO_2~--N对日本囊对虾24、48、72、96 h的半致死质量浓度(LC_(50))分别为1806.100、970.939、780.050、427.391 mg/L,安全质量浓度为42.739 mg/L。NO_2~--N质量浓度为151.36、239.88、380.19、602.56、954.99 mg/L的半致死时间(LT_(50))分别是120.008、111.954、94.207、78.810、60.102 h。试验表明,日本囊对虾养殖水体中NO_2~--N质量浓度应控制42.739 mg/L以下。     

消油剂对海湾扇贝(Argopecten irradians)的急性毒性效应

本研究以海湾扇贝(Argopecten irradians)为研究对象, 通过96 h半静水毒性实验，探讨了消油剂、0号柴油分散液(WAF)与0号柴油乳化液(CEWAF)对海湾扇贝24 h、48 h、72 h、96 h急性毒性效应。结果显示，消油剂对海湾扇贝的24 h、48 h、72 h和96 h半致死浓度(95%可信限)分别为1905(1570-2451 mg/L)、1293(1070-1556 mg/L)、1015(721-1348 mg/L)、846 mg/L(660-1020 mg/L)；WAF对海湾扇贝的24 h、48 h、72 h和96 h半致死浓度(95%可信限)分别为36.57(29.42-48.96 mg/L)、23.10(21.07-25.39 mg/L)、14.99(13.66-16.41 mg/L)、11.31 mg/L(8.37-14.47 mg/L)；CEWAF对海湾扇贝的24 h、48 h、72 h和96 h半致死浓度(95%可信限)分别为12.71(10.78-15.55 mg/L)、8.51 (7.99-9.07 mg/L)、6.56(4.46-7.74 mg/L)、5.42 mg/L(4.51-6.29 mg/L)。消油剂、0号柴油分散液、0号柴油乳化液对海湾扇贝96 h安全浓度分别为84.6、1.13、0.54 mg/L。随着实验时间的延长，消油剂、WAF和CEWAF对海湾扇贝的半致死浓度(LC50)均呈逐渐降低之势，半致死浓度与时间呈幂函数关系，其关系式分别为y=12242x–0.583、y=564.37x–0.848、y=89.987x–0.613。在受试溶液中暴露相同时间，海湾扇贝的半致死浓度从高到低依次为消油剂、WAF和CEWAF，说明CEWAF对海湾扇贝的毒性大于消油剂和WAF，这对于在养殖海区使用消油剂处理溢油事故具有重要的指导意义。     

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.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

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.