印度洋中西部大眼金枪鱼繁殖生物学的初步研究

根据2003年1~6月由中国农业部渔业局资助项目收集的渔业观察员数据和2004年1~6月印度洋中西部海域中国金枪鱼延绳钓生产调查数据,对所捕获的大眼金枪鱼繁殖生物学特征进行了初步研究。结果表明,渔获中性比均值为0.8,各月间的性比差异不显著。叉长小于85 cm或大于185cm时,渔获个体均为雄性;叉长为85~170 cm时,性比约为1.0。各月份大眼金枪鱼雌雄个体的性腺指数变动基本上保持一致,性腺指数随着月份增加而呈下降趋势。     

印度洋黄鳍金枪鱼生物学特性的初步研究

根据2003-2004年1-6月印度洋中西部海域金枪鱼延绳钓所捕获的黄鳍金枪鱼数据,对其基本的生物学特征进行了研究。结果表明,2003年和2004年渔获物中黄鳍金枪鱼加工后体重分别为7~81 kg和20~78kg,优势组分别为20~50 kg和30~60 kg。叉长范围分别为70~180 cm和110~170 cm。2003年渔获物雌雄性比的平均值为0.71,月间性比组成差异较小;2004年渔获雌雄性比的平均值为1.00,月间性比组成差异较大。2003年各月的摄食等级以1-2级为主,月间差异较小;2004年摄食等级以一级为主,并且月间各等级组成差异大。当渔获个体的叉长小于100 cm时,其性比组成波动较大;当渔获个体的叉长范围在100~150 cm之间时,性比组成的变化相对较小,基本上维持在0.5左右,也就是说雌雄个体数量大体保持平衡;当渔获个体的叉长大于160 cm时,所有样本个体均为雄性。体长与体重关系为W=2×10-5L2.9269。     

库克群岛海域海洋环境因子对沙氏刺鲅兼捕率的影响

为了减少沙氏刺鲅(Acanthocybium solandri)的兼捕率,文章利用2012年9月~2012年11月在南太平洋库克群岛海域延绳钓渔业调查数据(包括钓钩深度数据,温度、盐度和叶绿素a质量浓度垂直剖面数据,作业参数和渔获统计数据),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沙氏刺鲅的兼捕率与水层和温度的关系,并根据沙氏刺鲅兼捕率最高的水层推断得出其兼捕率最高的盐度和叶绿素a质量浓度范围。结果表明,库克群岛附近海域沙氏刺鲅兼捕率最高的水层和温度分别为40.0~80.0 m和26.0~28.0℃,推断得出沙氏刺鲅兼捕率最高的盐度段为36.30~36.90,叶绿素a质量浓度为0.070~0.243μg·L~(-1)。建议把钓钩深度设置到80 m以深、水温低于26℃、盐度高于36.90、叶绿素a质量浓度高于0.243μg·L~(-1)以减少延绳钓渔业中沙氏刺鲅的兼捕率。     

南海中北部尾明角灯鱼渔业生物学特性的初步研究

根据2014年和2015年在南海中北部海域中层拖网采集的尾明角灯鱼(Ceratoscopelus warmingii)样本,对其体长和体质量组成、性比、性腺成熟度和摄食等级等生物学特性进行了初步分析。结果显示,尾明角灯鱼的体长为32~76 mm,优势体长组为45~60 mm,占总数的86.9%,平均体长为(51.47±6.60)mm;体质量为0.3~4.3 g,优势体质量组为1.0~2.5 g,占总数的91.1%,平均体质量为(1.6±0.61)g;雌雄个体大小不存在显著差异(ANOVA,P0.05);生长参数b为2.581,表明尾明角灯鱼为异速生长;雌雄性比为1.39∶1,在不同月份、不同体长组中差异较大,10月和1月雌性比例远高于雄性;不同月份均有性成熟个体,性腺成熟度以Ⅰ期和Ⅱ期为主,性腺成熟比例最高为1月;初次性成熟体长为51.4 mm;摄食等级0~4级所占比例分别为10.8%、46%、33.9%、8.1%和1.3%。     

西北太平洋公海日本鲭生物学特征研究

日本鲭(Scomber japonicus)是西北太平洋公海灯光围网渔业捕捞的主要经济品种，具有巨大的开发利用价值。为全面了解其生物学特征，根据2016—2021年在该海域的渔业生产调查资料，对日本鲭叉长和体质量组成、叉长-体质量关系、性比、性腺成熟度、初次性成熟叉长、摄食等级和肥满度进行了研究。结果显示，其叉长和体质量呈双峰分布，叉长范围为102～400 mm,体质量范围为9.6～898.8 g。叉长-体质量关系式为W=1.303 84×10^-6L^{3.381 56},呈正向异速生长，性别对叉长-体质量关系影响不显著(P>0.05)。雌雄比例为1.74∶1,与1∶1差异显著(P<0.05);性成熟度以Ⅱ期为主，叉长对性腺成熟度的影响极显著(P<0.01);雌性和雄性初次性成熟叉长分别为(298.08±4.32) mm和(287.82±4.26) mm。摄食强度以1～3级为主，叉长显著影响摄食强度(P<0.05),性别对其影响不显著(P>0.05);肥满度范围为0.64～2.45,随叉长增加而增大。研究结果丰富了西北...     

南太平洋所罗门群岛海域黄鳍金枪鱼的渔业生物学特性

根据2010年8~10月,在南太平洋所罗门群岛海域延绳钓作业渔场所采集的黄鳍金枪鱼数据,对其渔业生物学特性进行了初步分析。结果表明,1）叉长为47.5~166.5 cm,平均叉长为112.7 cm,优势叉长为80.0~90.0 cm和100.0~140.0 cm（75.0%）;体重为2.0~72.0 kg,平均体重为26.5 kg,优势体重为5~10 kg和15~40 kg（68.6%）,雌、雄个体大小差异明显（ANOVA,P<0.01）;2）体重（RW）与叉长（FL）、纯重（DW）的关系分别为RW=1.159×10-5FL3.070和RW=1.118DW+0.684（不分性别）;3）雌、雄性比为1∶1.2。各叉长组性比变化显著（χ2=1 093.386,P<0.001）,叉长大于140 cm时,雄性个体占优势;4）性腺发育以Ⅱ期为主（50%）,初次性成熟叉长为113.4 cm。达到性成熟的个体中,34.0%的个体发育至Ⅴ期以上,说明调查期间为黄鳍金枪鱼繁殖期;5）空胃率高达51.6%,摄食种类主要为鱼类（67.5%）、头足类（18.0%）和甲壳类（14.5%）。不同叉长组的摄食等级存在显著变化（χ2=400.782,P<0.001）。     

印度洋中西部黄鳍金枪鱼生物学特性的初步研究

根据2003~2004年1~6月我国农业部印度洋金枪鱼延绳钓观察员项目所收集的有关数据,对印度洋中西部黄鳍金枪鱼的基本生物学特征进行了研究。结果表明,2003年和2004年渔获物中黄鳍金枪鱼加工后体重范围分别为7~81kg和20~78kg,优势组分别为20~50kg和30~60kg。叉长范围分别为70~180 cm和110~170 cm。2003年渔获物雌雄性比的平均值为0.71,月间性比组成差异较小;而2004年渔获雌雄性比的平均值为1.00,月间性比组成差异较大。2003年各月的摄食等级以1~2级为主,月间差异较小;而2004年摄食等级以1级为主,并且月间各等级组成差异大。体长与体重关系为W=2.1890×10-5L2.9269。     

热带中西太平洋海域大眼金枪鱼摄食生态学

为了解热带中西太平洋海域大眼金枪鱼(Thunnus obesus)的摄食生态学特性,利用金枪鱼延绳钓作业方式,于2018年5月—2019年2月期间,对该海域(2°03′S～11°17′S、163°14′E～173°35′E)的682尾大眼金枪鱼进行了食性分析,并使用方差分析(ANOVA)和有序多元Logistic回归模型,结合圆形统计方法分析了叉长、性别、性腺指数等生物因素以及渔获水深、月相等时空因素对摄食生态位宽度和摄食强度的影响。结果表明：1)叉长范围在81～195 cm的大眼金枪鱼雌雄个体的性别比例为1∶1.85;2)空胃率为25.4%,而在非空胃的个体胃含物中,枪乌贼属(Loligo sp.)、虾类和沙丁鱼属(Sardina sp.)的出现频率较高,依次为40.3%、39.7%、30.1%;3)个体摄食强度以0～2级为主,空胃率随着叉长的增加而增加,高摄食强度的比例随着渔获水深的增加而增加;4)方差分析(ANOVA)结果显示,性别、叉长、月相等因素对Shannon-Wiener多样性指数H′和Pielou均匀度指数J均没有显著影响,但渔获水深对J具有显著影响(P=0.024);...     

印度洋中南部大眼金枪鱼生物学特性研究

根据2008年9月~2009年4月在印度洋中南部金枪鱼延绳钓渔场调查期间收集的大眼金枪鱼生物学数据,对其基本的生物学特征进行了研究。结果表明:(1)叉长范围为57~184 cm,优势叉长组为101~110cm和121~130 cm,约占总数的41.7%,平均叉长为119.5 cm;(2)不分性别大眼金枪鱼叉长(FL)与加工后重(DW)的关系可表达为:DW=2.407 6×10-5FL2.931 6,雌雄个体差异不显著(F=0.207,P0.05);(3)调查期间,大眼金枪鱼雄性比例为56.55%,当叉长大于140 cm时,雄性占优势;调查期间,该海域大眼金枪鱼的繁殖期为10月~翌年4月,繁殖峰期为10月~翌年1月;(4)摄食种类中柔鱼、帆蜥鱼和虾类所占比重较高,分别占36.0%、20.1%和18.0%;各月份摄食等级1~4级分布呈显著性差异(χ2=191.20,P0.01),各叉长组大眼金枪鱼摄食等级变化无显著性差异(χ2=41.08,P0.05)。     

温台渔场日本鲭的繁殖生物学特征

利用2012年春季在温台渔场对日本鲭(Scomber japonicus)繁殖群体连续6批取样的生物学测定数据,对其繁殖生物学特征进行了研究。结果表明,叉长340 mm以下群体中,雌雄比基本符合1∶1的性比关系;叉长340 mm以上群体中,雌鱼显著多于雄鱼(P0.05)。GSI随时间的变化结果显示,温台渔场日本鲭的主要繁殖期为3月中旬至4月中旬;不同时间段的雌鱼和雄鱼GSI均总体表现为雌鱼大于雄鱼(P0.05)。不同性腺发育阶段的平均摄食强度总体表现为雄鱼大于雌鱼。不同性腺发育阶段的雌性和雄性的肝指数均雌性显著大于雄性(P0.05)。绝对繁殖力范围为44 017~734 684粒/尾,平均值为(173 867±15 719)粒/尾,优势组为(10~30)×104粒/尾,占70.37%;相对繁殖力范围为187~1 403粒/g,平均值为(538±31)粒/g,优势组为(390~700)粒/g,占66.67%。卵径范围为0.27~1.22 mm,平均值为(0.86±0.01)mm,优势组为0.7~1.1 mm。温台渔场日本鲭的绝对繁殖力低于黄海北部而高于台湾海峡,相对繁殖力高于历史水平,平均卵径小于20世纪80年代,雌雄鱼的最小性成熟叉长均有一定程度的降低。以上结果都说明日本鲭为应对高强度捕捞和环境胁迫压力而采取增加相对繁殖力、减小卵径、提早性成熟等繁殖策略来维持种群数量和保证种群的延续。     

Rare serotype occurrence and PFGE genotypic diversity of Streptococcus agalactiae isolated from tilapia in China

Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China.     

Growth hormone (GH) and reproduction: a review

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Controlled infection of Poecilia reticulata Peters (guppy) with Tetrahymena by immersion and intraperitoneal injection

Tetrahymena is a protozoan parasite, which infects guppy, Poecilia reticulata Peters, and causes substantial economical losses in commercial farms worldwide. Studies of guppy infected by Tetrahymena require standardized infection protocols. The LD50 for Tetrahymena infection of guppies by intraperitoneal (IP) injection was calibrated, and the level obtained was 946 parasites per fish. Guppy infection with Tetrahymena by immersion, imitating the natural route of infection via the integument, was studied under normal or stress conditions. Exposure to cold and netting (CNI) and to cold only (CI) followed by immersion exposure to 10 000 Tetrahymena per mL resulted in 22.5% and 19.2% mortality, respectively, as compared to 14.2% and 10% in groups that were netted only (NI) or non‐stressed (I). Histopathology revealed that immersion infection resulted in a systemic infection. Lysozyme levels, measured 3 weeks after infection, were significantly higher in the CNI group (288 μg per mg protein) compared with CI‐, NI‐ and I‐treated groups (94.5, 64 and 62.3 μg mg^?1, respectively). There was no evident parasite immobilization activity in body homogenates, suggesting no development of acquired immunity. Re‐infection by IP injection revealed no increase in protection in any of the treatment groups, mortality range of 56.3–75%, higher than in the non‐exposed control (40.6% mortality).     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Effect of iodophor disinfection of non‐hardened Salmo trutta eggs on their bacterial and fungus load

This study investigated the efficiency of iodophor disinfection (135 ppm active iodine for 15–30 min) of non‐hardened Salmo trutta eggs against different groups of bacteria and against fungus. Egg samples were taken from non‐disinfected and from disinfected eggs, microorganisms were cultured on specific nutrient media and their mass was measured by turbidimetric methods. Bacteria and fungus mass of non‐hardened eggs could be reduced but not eliminated by iodophor disinfection with 135 ppm active iodine for 15 min. The extent of reduction was 47–65% (Experiment 1). The efficiency of disinfection increased with disinfection time as the reduction in bacteria and fungus mass was 40–55% after 15 min and 58–74% after 30 min (Experiment 2). Disinfection efficiency of iodophor solution diluted in water (reduction 49–57%) and of iodophor solution diluted in sodium chloride solution iso‐osmolar to the oocytes (reduction 52–61%) was similar (Experiment 3). The reduction in bacteria and fungus mass was persistent as it was 39–72% lower in embryos deriving from disinfected eggs than in embryos deriving from non‐disinfected ones (Experiment 4). In conclusion, the tested disinfection method is inadequate to eliminate pathogens completely but it could positively influence immune defence of eggs and embryos.     

Nitrogenous waste excretion and accumulation of urea and ammonia inChalcalburnus tarichi (Cyprinidae), endemic to the extremely alkaline Lake Van (Eastern Turkey)

The endemic, anadromous cyprinidChalcalburnus tarichi is the only fish species known to occur in alkaline Lake Van (Eastern Anatolia, Turkey). EightC. tarichi were maintained individually in Lake Van water (17 – 19°C; pH 9.8; 153 mEq·I^–1 total alkalinity; 22 total salinity) and tank water samples analyzed for 24 h in 2 to 4 h intervals. At zero time, < 1µM ammonia was present and urea was undetectable in the tank water; at 24 h, total ammonia and urea made up 114±32 and 35±25µM, respectively. Over the experimental period, ammonia-N and urea-N excretion averaged 1041±494 and 607±169moles·kg^–1 fish·h^–1, respectively. The extent of urea excretion was highly variable between specimens. Uric acid excretion was not detectable.Urea was present at high concentrations in all tissues and plasma (25 – 35moles·g^–1·ml^–1) of freshly caughtC. tarichi; total ammonia content of the tissues was by a factor of 1.9 (liver) to 3.0 (brain) lower. High arginase activity (2.4±0.2 U·min^–1·g^–1) was detected in the liver ofC. tarichi but ornithine carbamoylphosphate transferase, a key enzyme of the ornithine-urea-cycle, was absent. Ureagenesis is likely through degradation of arginine and/or uricolysis. High glutamine synthetase activity (11±0.6 U·min^–1·g^–1) and low ammonia content in brain suggest that, like other teleosts,C. tarichi has an efficient ammonia detoxification in the brain, but in no other tissue.Nitrogenous waste excretion at alkaline pH is discussed. The ability ofC. tarichi to excrete high levels of ammonia at extremely alkaline pH is unique among teleosts studied so far. The mechanism of ammonia excretion under Lake Van conditions remains to be elucidated.     

Influence of the antibacterial herbs, Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia on the survival, growth and bacterial load of Penaeus monodon post larvae

The indiscriminate use of antibiotics and chemicals in shrimp hatcheries has led to biomagnification and that in turn could lead to rejection of a whole consignment. The application of the bioencapsulation technique as a tool for curative treatment in shrimp larvae was investigated. Herbs having antibacterial properties such as Solanum trilobatum, Andrographis paniculata and Psoralea corylifolia (methanolic extracts) were bioencapsulated in Artemia and fed to Penaeus monodon post larvae PL 1–25. The post larvae were reared in a medium inoculated with pathogenic bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella typhi and Vibrio sp. Post larvae reared in the non-inoculated water and fed with non-enriched Artemia exhibited 90% survival, highest specific growth rate (12.43%) and reduced bacterial load. P. monodon reared in the bacterial inoculated water and fed with the non-enriched Artemia exhibited the lowest survival (10–30%), specific growth rate (8.42–9.1%) and increased bacterial load (2.86 × 10³ to 3.76 × 10⁵ cfu/g). The methanolic extracts of the herbs helped to increase survival and specific growth rate and reduced bacterial load in the P. monodon culture system. Among the three herbal extracts, P. corylifolia enriched Artemia fed post larvae showed the tendency to higher survival (>50%), growth rate (11.5 averaged) and low bacterial load (1.12 × 10⁵ cfu/g). This revised version was published online in August 2006 with corrections to the Cover Date.