黄海不同型刺网的渔获选择性比较

为提高近海渔业资源养护型捕捞与管理技术,促进《全国海洋捕捞渔具目录》的实施,2014年9—10月在黄海进行了网目尺寸为40、50、60 mm的单片型刺网、双重型刺网和三重型刺网以及生产对照网的选择性对比试验。试验结果表明,相同网目尺寸的各型试验网的渔获种类间呈中等相似或极相似;渔获优势种为高眼鲽、细纹狮子鱼、黄、小黄鱼和白姑鱼,不同试验网的渔获优势种不同。40、50、60 mm的三重型刺网的单位捕捞努力量渔获量分别为相同网目尺寸的单片型刺网单位捕捞努力量渔获量的187%、174%和146%,对应的经济效益分别为单片型刺网经济效益的133%、112%和184%,小黄鱼幼鱼比例分别为单片型刺网的162%、342%和122%,高眼鲽幼鱼比例分别为单片型刺网的108%、277%和100%。渔获结构显示,单片型刺网对小黄鱼、鲐鱼和白姑鱼等纺锤型鱼类的选择性优于三重型刺网,而三重型刺网对高眼鲽、黄鮟鱇的选择性具有明显优势。     

浙江近海棘头梅童鱼生长规律与群体组成的研究

本文根据浙江近海棘头梅童鱼的生物学测定资料,应用Von Bertalanffy鱼类生长方程分析棘头梅童鱼的生长规律,并与另外几种石首鱼科鱼类进行比较,显示出梅童鱼具有寿命短、生长迅速特性。同时,通过对棘头梅童鱼群体组成分析,认为浙江近海捕捞以采用梅童鱼拖网或定置刺网为好,渔期以冬春季比较适宜。     

辽东湾口虾蛄流刺网的渔获选择性研究

为了提高近海渔业资源养护型捕捞与管理技术,促进《全国海洋捕捞渔具目录》的实施,2014年10—11月在辽东湾以口虾蛄为目标渔获,进行了网目尺寸为40、50、60mm的单片型刺网、双重型刺网、三重型刺网以及生产对照网的选择性对比试验,为确定渤海三重型刺网管理的过渡归属提供依据。结果显示,各试验网具的主要渔获种类基本相同,渔获优势种为口虾蛄和花鲈,随着网目尺寸的增大,各型刺网的口虾蛄相对重要性指数递减,而花鲈相对重要性指数则呈递增趋势。单片型刺网、双重型刺网和三重型刺网间的口虾蛄渔获量差异显著(P=0.04,P=0.66×10-6,P=0.029),口虾蛄渔获尾数占总渔获的比例呈现出按单片型刺网、双重型刺网、三重型刺网顺序增长的趋势。相同网目尺寸条件下,未达到可捕标准的口虾蛄渔获尾数呈现出按单片型刺网、双重型刺网、三重型刺网顺序递增的趋势,但其所占比例并无明显差别;相同型的刺网,随网目尺寸的增大未达到可捕标准口虾蛄的渔获比例递减。Gamma选择性模型曲线显示,当网目尺寸大于50mm时,单片型刺网、双重型刺网、三重型刺网的口虾蛄渔获优势体长均大于可捕标准,但是三重型刺网的渔获数量明显大于单片型刺网,且在渔业资源损害方面并无明显差别,因此,在目前渤海的口虾蛄渔业中,单片型刺网难以取代三重型刺网进行作业。     

渤海口虾蛄三重刺网渔获组成及其捕捞性能分析

为研究渤海口虾蛄(Oratosquilla oratoria)三重刺网的捕捞性能,以河北省昌黎县的口虾蛄三重刺网为基础,于2013年4、5、7月在河北省秦皇岛近海进行50 mm、55 mm、60 mm和65 mm 4种网目尺寸的三重刺网作业性能比较实验,并与60 mm网目单片刺网和底拖网进行渔获对比分析。结果表明:三重刺网具有捕获渔场中绝大多数渔业种类的能力,选择能力较差。春季的渔获种类19种,为渤海近岸底层种类;夏季的渔获种类19种,除了小黄鱼(Pseudosciaena polyactis)和带鱼(Trichiurus lepturus)等底层鱼类外,还有日本鲭(Scomber japonicus)和蓝点马鲛(Scomberomorus niphonius)等中上层鱼类。春季的渔获结构单一,口虾蛄占渔获量的90%以上,主要兼捕种类鲜明鼓虾(Alpheus distinguendus)占4.1%,渔获选择性较好;夏季的渔获中,口虾蛄比例在75%左右,兼捕对象主要为小黄鱼、蓝点马鲛等经济鱼类的幼鱼,对渔业资源造成一定程度的损害,但渔获选择性比底拖网好。单片刺网的选择性最好,但渔获量低,只有三重刺网渔获量的30%左右,无法满足生产要求。建议开展渤海口虾蛄的可捕产量和分区域捕捞管理研究,开发作业性能更优越的口虾蛄专业捕捞渔具。     

辽东湾不同型刺网捕捞性能的比较

为了提高近海渔业资源养护型捕捞与管理技术,促进《全国海洋捕捞渔具目录》的实施,2014年10-11月在辽东湾进行了网目尺寸为40 mm、50 mm、60 mm的单片刺网、双重刺网和三重刺网以及生产对照网的选择性对比实验.结果显示,各种实验网的渔获种类数均在6-9种之间,优势种口虾蛄(Oratosquilla oratoria)的优势度随网目尺寸的增大而减小,但花鲈(Lateolabrax japonicas)的优势度随网目尺寸的增大而增大.同型试验网在不同网目尺寸条件下的渔获量有显著性差异,其中,60 mm试验网与40 mm同型试验网的单位捕捞努力量渔获量(CPUE)比较,单片刺网为800％,双重刺网为650％,三重刺网为500％;而异型试验网在网目尺寸相同条件下对渔获量的影响相对较小.试验网的组内渔获组成平均相似度分别为单片刺网59.24％,双重刺网62.63％,三重刺网66.51％;组间分别为71.44％、67.50％和70.58％;对组内和组间平均相似度贡献最高的种类均为口虾蛄和花鲈.随着网目尺寸的增大,各型试验网的渔获物幼鱼比例呈下降趋势.     

不同网具在人工鱼礁水平方向上诱集效果的比较

为了解东海典型软相泥地生境鱼礁投放后在水平梯度上的影响能力,于2014年8月在嵊泗人工鱼礁区采用等间距设点的方法,对不同网具(刺网、地笼网、拖网)在评价人工鱼礁区鱼类和大型无脊椎动物组成方面的应用效果进行了初步探讨。结果表明,刺网渔获组成以鱼类为主,占刺网总渔获种类的51.1%;拖网主要为节肢类,其次是鱼类,分别占拖网总渔获种类的41%和37.7%;地笼网的渔获种类分布则较为均衡。比较不同采样方法在鱼礁区水平方向上多样性的表征能力,拖网优于刺网和地笼网,3种网具组合的采样方式优于单种网具或任意两种网具相互组合。自人工鱼礁核心区向外,各站点生物资源量、多样性等指标大致呈逐渐减少的趋势。从上述指标的空间差异来看,三横山鱼礁区的有效辐射距离约为200 m,而东库山鱼礁区辐射距离为200~300 m。研究结论认为,相对于单一采样方法,组合刺网、地笼网和改进型底拖网的综合采样方式可以获得更完整的现场信息,从而更好地揭示人工鱼礁投放后水平方向的资源分布和群落结构状况。     

枸杞岛筏式贻贝养殖海域鱼类群聚特征

为探究筏式贻贝养殖生境鱼类资源养护功能,于2020年9－12月对枸杞岛筏式贻贝养殖生境(分表层区和底层区)及周边岩礁生境的鱼类进行了多网目组合刺网采样。应用相对重要性指数IRI、多样性指数并结合等级聚类、非度量多维标度排序(nMDS)分析鱼类组成和群落结构。结果显示,在2种生境中共采集鱼类55 种,隶属于10目34科47属,其中贻贝养殖生境采集到37种(底层和表层分别为29和20种);岩礁生境共采集到40种。在鱼类组成上,中国花鲈和鲻是贻贝养殖生境表层区的典型优势种,而黄姑鱼和褐菖鲉是贻贝养殖生境底层区的典型优势种;褐菖鲉同时也是岩礁生境的典型优势种。多样性分析表明,贻贝养殖生境的总体鱼类多样性要高于岩礁生境,但尚不显著。多元分析显示,各月份2种生境中的鱼类群落格局均可分为3种类型,虽与养殖表层区、养殖底层区和岩礁区并非严格一致,但各群落间差异依然显著。研究表明,大规模筏式养殖设施的存在吸引了众多中上层鱼类及底层鱼类,也为岩礁生境优势鱼类提供了额外的栖息环境,发挥了近似于浮鱼礁系统的资源养护作用。研究结果可为岛礁海域海洋牧场目标种的选择和人工生境构建模式的应用提供重要参考。     

枸杞岛海藻场优势种鱼类群体特征及其在不同生境中的差异

为了解枸杞岛岩礁不同底栖海藻分布的海藻场区域鱼类优势群体组成和分布特征,于2009年2月—2010年2月对枸杞岛海藻场和沙地生境的鱼类进行了逐月采样,对其中的鱼类优势种群组成、生物学特征和摄食规律作了比较。结果表明,以大型底栖海藻铜藻为优势种和以孔石莼等小型底栖海藻为优势种的海藻场鱼类全年优势种皆为褐菖鲉、斑头鱼和黄姑鱼。褐菖鲉群体具有近岸活动频繁、群体低龄和小型化、丰度年间变化大的特点,通过性成熟提前、雌性比例远高于雄性、摄食对象多样化的方式应对生存压力,维持对整个群体的补充。斑头鱼和黄姑鱼群体都具有低龄化现象,群体补充主要受洄游群体影响。3种鱼类因生活习性和摄食对象的不同,表现出个体间的生长差异。同时,由于发育不同阶段的食性转化、体型变化和来自上层捕食者的捕食压力,褐菖鲉和黄姑鱼会随着发育阶段的变化,表现出对不同生境的选择利用。斑头鱼食性较为稳定,其活动区域由主要的摄食对象麦秆虫所主导,主要栖息于海藻场生境。     

中沙、南沙群岛礁盘深水域中下层鱼类资源开发利用技术研究

我国中沙、南沙群岛礁盘众多,海域广阔,渔业资源丰富,是刺网和钓钩深水捕捞作业的理想渔场。近三年来,海南省琼海市渔民应用定置刺网渔具探捕了中沙、南沙群岛礁盘60－140米深中下层水域鱼类资源状况,获取第一手资料。经初步整理分析结果,本文报告此水域中下层鱼类种类组成及资源状况,共记录了鱼类种类有116种,分隶于13目30科属和甲壳类3种。渔获物总上网率为63.81kg／1000m,其中,软骨鱼类为51．00kg／100m,硬骨鱼类为1280kg／1000m。不同网目大小的三种定置刺网,以大网目三层定置利网的渔获量最佳,渔获率为94．23kg/1000m,捕…     

三重刺网摘鱼技巧

三重刺网的设计原理虽然有针对性地解决了水域中１公斤以上大个体鲢鳙等鱼类的捕捞问题，却出现了新的先天性缺陷———摘取渔获物比单片刺网更加费时费力，本文总结了常规性和特殊性情形的摘鱼操作法。在通常情况下，采用常规性摘鱼法。首先，辨清鱼上网的方向，给囊袋定向。起网时，人为规定三重刺网与船舷直接接触的一片大网目网衣为刺网的反面，另一片大网目网衣为刺网的正面。当鱼从正面方向上网而在刺网的反面形成囊袋称之为正方袋；反之则称为反方袋。在起网拉收主网衣进船舱过程中，眼见或手感觉到水中网衣缠有渔获物时，收网动作应…     

Anguilla huangi Teng, Lin, and Tzeng, 2009, is a junior synonym of Anguilla luzonensis Watanabe, Aoyama, and Tsukamoto, 2009

Anguilla luzonensis and A. huangi were each described in 2009 using eels obtained from northern Luzon Island. We examined the taxonomic status of these two groups of eels using morphological and molecular genetic characters. There were no significant differences in two vertebrae counts between eels of A. luzonensis and A. huangi. Mitochondrial 16S ribosomal RNA and cytochrome b genes sequences were obtained and compared among 28 specimens of A. luzonensis, the holotypes of A. luzonensis and A. huangi, and one specimen of the other 15 anguillid species. The specimens of A. luzonensis exhibited almost identical sequences, including the holotype, with only a few site differences, and the genetic difference between the holotypes of A. luzonensis and A. huangi was within the range of differences of specimens of A. luzonensis. The other anguillid species were genetically very different from A. luzonensis and A. huangi, although A. interioris is a closely related species. It is clear that A. luzonensis and A. huangi are the same species, and according to the principle of priority in zoological nomenclature, A. luzonensis Watanabe, Aoyama, and Tsukamoto, 2009 is the valid species name, and A. huangi Teng, Lin, and Tzeng, 2009 is a junior synonym of A. luzonensis.     

Surface disinfection of Pacific threadfin, Polydactylus sexfilis, and amberjack, Seriola rivoliana, eggs

The effects of exposing the eggs of Pacific threadfin and amberjack eggs (AEs) to different concentrations of hydrogen peroxide for 5 min on hatch rate and survival were assessed in a series of experiments using a petri dish model rearing system. Despite significant inter‐batch variation in hatch rate, it was shown that eggs of both species could be safely exposed to up to 11 340 mg L⁻¹ H₂O₂ for 5 min. Exposure to 34 230 mg L⁻¹ H₂O₂ for 5 min was shown to be lethal to AEs at a late stage of development. In two further experiments, it was demonstrated that Pacific threadfin eggs were resistant to all tested concentrations of a range of polyvinylpyrrolidone iodine (PVP‐I) concentrations and contact times (up to 1000 mg L⁻¹ PVP‐I for 10 min). The level of bacteria adhering to the eggs of both species was highly variable. Where eggs were heavily colonized (>10⁴ cfu egg⁻¹), hydrogen peroxide concentrations of at least 11 340 mg L⁻¹, or PVP‐I concentrations higher than 500 mg L⁻¹ for 10 min, were required for effective sterilization. In less colonized batches, rinsing in sterile seawater or exposure to lower (550 mg L⁻¹) concentrations of H₂O₂ was sufficient to result in high apparent levels of surface sterility (<1 cfu egg⁻¹).     

Effect of Lead on Survival,Osmoregulation, and Histological Changes of the Gills of the White Shrimp,Litopenaeus vannamei,Boone, 1931

The purpose of this study was to evaluate the acute toxicity of lead for different life stages of shrimp, Litopenaeus vannamei, and to determine the effect of its sublethal concentrations on osmoregulatory capacity (OC) as well as the possible histological alteration in the gills of juvenile shrimp. The 24‐, 48‐, and 96‐h LC₅₀ values for lead to L. vannamei increased progressively with increasing life stage, from nauplii < zoeae < mysis < postlarvae < juvenile. After 15‐d exposure to 3.25, 6.50, and 9.75 mg Pb/L, the OC values of exposed shrimp were reduced by 39, 73, and 157%, respectively compared to control animals. Compared to controls, the lead concentrations in gill tissues increased significantly by 127,500, 137,500, and 141,000% in shrimps exposed to 3.25, 6.50, and 9.75 mg Pb/L, respectively. After lead exposure, hemocytic congestion in efferent vessels and multiple hyperplasia were observed in gill filaments, resulting in narrowed hemolymphatic lacuna. The histopathological effects increased with increasing Pb concentration.     

驼背鲈(Chromileptes altivelis)的胚胎发育及仔、稚、幼鱼形态观察

对驼背鲈(Chromileptes altivelis)的胚胎发育及仔、稚、幼鱼的形态特征进行了详细的观察与研究,描述了从受精卵到仔、稚、幼鱼各发育期的时间和形态特征变化。结果表明,在水温25-26℃、盐度30的海水中,受精卵历时27 h 25 min完成整个胚胎发育过程,经历从卵裂、囊胚、原肠、神经胚到肌节形成、各器官的逐渐形成、变化、完善等一系列的胚胎发育和变化过程;根据其卵黄囊消长情况、鳞片的覆盖状态、体色发生的不同变化以及第二背鳍和腹鳍的消长,将胚后发育分为仔、稚、幼鱼3个阶段。在水温22-26℃、盐度29-31、DO≥5 mg/L的条件下,2-3 d仔鱼卵黄囊消失,开口摄食;生长发育至31 d,仔鱼已变态进入稚鱼期;培育至57 d,稚鱼完成变态,成为幼鱼。第二背鳍棘和腹鳍棘的生长与收缩等石斑鱼类早期发育的共性生长特征及其体表特性体色变化特征为驼背鲈胚后发育过程中最明显的特征。     

Effects of Mosquitofish,Gambusia affinis,on Channel Catfish,Ictalurus puncatatus,Production Ponds

Mosquitofish, Gambusia sp., have been spread throughout the world to biologically control mosquitoes. However, the fish has gained a reputation as an invasive species and has been implicated in displacing native aquatic species. Gambusia affinis are native to the southeastern United States and commonly occur in commercial channel catfish, Ictalurus punctatus, production ponds. We investigated effects of mosquitofish presence on zooplankton populations, water quality, disease occurrence, and fish production in experimental ponds. There were no differences between ponds with or without mosquitofish in numbers of calanoid copepods, cyclopoid copepods, total copepods, Bosmina sp., Ceriodaphnia sp., Moina sp., Daphnia sp., or total cladocerans. There were also no differences in copepod and cladoceran sizes. Copepod nauplii were more numerous during the summer months in ponds with mosquitofish. There were no differences in water quality variables (soluble reactive phosphorus, nitrate, nitrite, ammonia, total nitrogen, total phosphorus, pH) or phytoplankton density between ponds stocked with and without mosquitofish. Catfish production and disease occurrence were also similar between ponds with and without mosquitofish. Although mosquitofish may cause problems when stocked outside their native range, there does not appear to be any adverse effects of mosquitofish presence in catfish production ponds.     

Effect of Temperature on Growth,Energy Budget,and Physiological Performance of Green,White, and Purple Color Morphs of Sea Cucumber,Apostichopus japonicus

As an intertidal species, Apostichopus japonicus is subject to diel and seasonal temperature fluctuations. Color variation is a distinct characteristic of A. japonicus, and a new color morph, purple A. japonicus, was recently found on the coast of Rushan, Weihai City. This study was conducted to compare the performance of green, white, and purple color morphs of A. japonicus at different water temperatures to help improving aquaculture technology and management. In this study, green, white, and purple color morphs of juvenile A. japonicus (1.5 ± 0.1 g) were cultured at 10, 14, 18, 22, and 26 C for 60 d, according to the suitable temperature range for sea cucumber growth. Temperature was shown to have a significant effect on growth, energy budget, and physiology of sea cucumbers (P < 0.05). Specific growth rates, feed conversion efficiencies, and the proportion of energy allocated to growth of all three color morphs were optimal at 18 C. Activities of the enzymes related with oxidative stress, immune response, and digestion were determined. Superoxide dismutase (SOD) and trypsin activities generally reached a maximum in all three color morphs at 18 C. The purple color morph of A. japonicus was higher in growth rate, food conversion efficiency, and proportion of energy allocated to growth than green and white color morphs at 18 and 22 C, consistent with its higher trypsin and SOD activity, indicating the mutual effect of growth and physiology. At 18, 22, and 26 C, the green color morph had the highest level of lysozyme activity and purple color morph had the lowest, indicating possible infection by external pathogens of green color morph, which might be caused by high temperature. These results suggested that the optimum temperature for culture of the three color morphs was approximately 18 C, the purple had a better adaption to high temperature, and the green and white color morphs may be more susceptible to thermal stress than the purple color morph.     

Age,growth, maturity and the overfishing of the iconic sciaenid,Argyrosomus japonicus,in south-eastern,Australia

Mulloway (Argyrosomus japonicus) occur in estuarine and coastal waters surrounding Australia, Africa, India, Pakistan, China, Korea and Japan, where they are important in fisheries. This study identified that mulloway in south-eastern Australia had similar growth rates, but matured at smaller lengths and younger ages, to those in South Africa and Western Australia. Growth of both sexes was similar to about 5 years, after which females grew faster and attained a greater maximum length than males. Female mulloway matured at 4–5 years of age with a L₅₀ of 68 cm, whereas males matured at 2–3 years of age with a L₅₀ of 51 cm. The commercial fishery in New South Wales was characterised by declining catches and a reduction in the proportion of mulloway of mature lengths in landings. During 2002–2005 commercial landings were dominated (83%) by fish within 15 cm of the current minimum legal total length of 45 cm and aged 2 and 3 years (>80%), even though mulloway can attain lengths of 200 cm and live >30 years. Estimates of the rates of instantaneous total mortality ranged between 0.34 and 0.45, whilst the rate of instantaneous natural mortality (M) was estimated to be approximately 0.12. Yield-per-recruit analyses indicated that mulloway in New South Wales are being growth overfished and substantial increases in yield could be achieved by increasing the length at first harvest. Values of the spawning potential ratio were below 0.2 under a range of mortality estimates, suggesting that mulloway are at risk of recruitment overfishing. These results suggest that the spawning stock of mulloway in south-eastern Australia has been depleted and that remedial management action is required to protect this iconic species.     

Recruitment strategy of swimming crab, Portunus trituberculatus, in Hiuchi-Nada, Japan

The recruitment strategy of swimming crabs, Portunus trituberculatus, was investigated by field observations and numerical experiments in Hiuchi-Nada, Japan. Calculated dispersal patterns of zoeal and megalopal stages in a three-dimensional numerical model reproduce observed patterns accurately. The temporal change of vertical migration patterns between the 1st and 2nd zoeas and the 3rd and 4th zoeas plays an important role in the process of recruitment of P. trituberculatus from spawning ground to nursery ground.     

Effect of Salinity on Embryonic Development,Hatchability, and Growth of African Catfish,Clarias gariepinus,Eggs and Larvae

Abstract

Effects of salinity on embryonic development and growth of African catfish, Clarias gariepinus, eggs and larvae were studied. Eggs were incubated at 27-29°C in 2,4,6,8, and 10 ppt sodium chloride. Rate of embryonic development was delayed in all salt solutions by 15, 15,28 and 30 minutes, in 2,4,6, and 8 ppt sodium chloride, respectively, when compared with the control group (0% salt); total mortality occurred at 12 hours after gastrula stage in the 10 ppt concentration. Percentage hatching was 45.1,47.7, 59.5,49.2, and 26.6% while percentage deformity was 10.4, 16.1, 52.0, 28.6, and 71.6% in 0, 2, 4, 6, 8, and 10 ppt salt treatments, respectively. There were significant differences (P <0.05) in the hatching percentage and in deformity percentage between 4, 6, and 8 ppt. Rate of yolk absorption was significantly faster in the control and 2 ppt salt treatments, but slower in 4, 6, and 8 ppt. Rate of increase in length was slower with increasing salinity. The optimum salinity for African catfish eggs and was between 0-2 ppt and acceptable up to 6 ppt. The results suggest that increasing salinity delayed hatching and development of African catfish eggs and larvae, respectively, as well as increased the deformity of the larvae.     

Effect of Stocking Density on Growth,Yield, and Costs of Producing Rainbow Trout,Oncorhynchus mykiss,in Cages

Abstract

Rainbow trout, Oncorhynchus mykiss, were raised in culture cages (1 m³) to determine the effect of stocking density on growth, survival, and percentage of market-size fish. Large fingerling rainbow trout (20-25 cm, 232 g average weight) were stocked into six cages located in a 0.4-ha pond. Two stocking densities (100 or 200 fish/cage) were used, and fish were grown for 140 days (2000-April 2001). Average total harvest weight (35.0 kg) in the low-density cages was approximately one-half the average total harvest weight (61.2 kg) in the high-density cages. Average weight gain (11.7 kg to 15.1 kg) and feed conversion (1.2 to 1.5) were also smaller for the low-density cages. Average survival was 96.7% for the low-density cages and 94.2% for the high-density cages, with the percentage of market-size fish (< 29 cm) averaging 50.3% and 52.0%, respectively. Production costs for the actual experiment and the revenues from fish sold at the end of the study were collected. An enterprise budget based on the experimental results for the two densities was developed to determine if a culture operation of this size would produce a net return. Production costs and revenues from the experiment resulted in a large negative return (-$3,124) and high breakeven price ($13.53/kg).