The reproductive cycle of the ‘blunt’ sea urchin

The reproductive cycle of the blunt sea urchin, Sphaerechinus granularis (Lamarck), was studied in the Bay of Brest, West Brittany, from monthly samples by examining seasonal changes in gonadal index, in the stages of gonad development and in oocyte diameters. This echinoid exhibited an annual cycle of gonadal growth, with a short breeding season occurring in May and June, and a decrease in gonadal index during the winter attributed to the use of nutrient resources. Histological examinations defined long mature stages during autumn, winter and early spring, where the vitellogenic oocytes accumulated in the lumen of the gonad. Changes in oocyte diameters showed a short pre-spawning period in April and May. The brief breeding season was followed by rapid post-spawning recovery and gonad growing stages during the summer, where the gonads mainly grew through the development of nutritive tissue. The features of this reproductive cycle show that the species can be commercially exploited and these results are used to make recommendations in terms of the management of S. granularis fisheries in Brittany. The influence of temperature on the initiation of spawning was noted again. This exogenous factor could be monitored to improve gonad production and availability of mature gametes in mariculture projects. © Rapid Science Ltd. 1998     

Potential effects of global climate change on fisheries in the Trasimeno Lake (Italy), with special reference to the goldfish Carassius auratus invasion and the endemic southern pike Esox cisalpinus decline

Global climate changes have led to a gradual warming of the planet, resulting in decreased precipitation and rising temperatures in Mediterranean inland waters. In Trasimeno Lake, the largest shallow lake in Italy, some non‐native fish species have probably benefited from these changes as they are thermophilic and characterised by wider habitat preferences. Fish data collected by gillnets and fyke nets between 1956 and 2016, and by electrofishing in 1993 and 2014, were used to analyse changes over time in the fish community in relation to environmental conditions. An explosion in goldfish Carassius auratus (L.), following its introduction in 1988, coupled with water level fluctuations and reduced transparency, contributed to the reduction in commercial fish catch in the lake, and to the decline of the endemic southern pike Esox cisalpinus Bianco & Delmastro, already threatened by reduced spawning habitat and interspecific competition with other non‐native predatory fishes.     

Using fish landing sites and markets information towards quantification of the blue economy to enhance fisheries management

Fisheries management uses important fish market information and information from Communication Technology (ICT) to improve fish trade by identifying inefficiencies, inequity and post‐harvest losses. The current study reports fisheries output using ICT at major landing sites and markets in Kenya and Uganda from the Kenya Marine and Fisheries Research Institute (KMFRI) Enhanced Fish Market Information Service (EFMIS) database for 2009 – 2017. Catch assessment survey data validated the use of market data in drawing conclusions. Regional Frame Survey data provided information before EFMIS, enabling comparisons of fish trade costings. The average quantity of fish traded in Kenya depended on seasons of active lake fishing, which occurs in January – March and August – October, while Uganda had an irregular pattern associated with fish trade throughout the year. The quantity of fish traded weekly depended on the average price of fish. Lower sales margins during the EFMIS project showed the merits of information sharing using ICT platforms for efficient and equitable fish trade. Such evaluation of fish market information is useful in fish trade policy formulation and for fisheries management and ecological sustainability in rural and peri‐urban communities.     

Episodic recruitment of young Prochilodus lineatus (Valenciennes, 1836) (Characiformes: Prochilodontidae) during high discharge in a floodplain lake of the River Paraná, Argentina

Prochilodus lineatus (Val.) is one of the main target species of South American freshwater fisheries. The following null hypotheses regarding juvenile recruitment of P. lineatus were tested: (a) recruitment is not determined by variations in larval abundance and (b) recruitment is not determined by variations in discharge. For this purpose, variations in abundance of larvae in main channel drift and monthly captures of juveniles in a floodplain lake of the River Paraná were examined weekly between 2009 and 2016. Mean annual abundances of larval densities and CPUE of juveniles were correlated with a set of hydrometric variables. A positive correlation was found between the abundance of juveniles with high and persistent flood pulses. By contrast, larval abundance was not correlated with juvenile abundance. Pronounced contrast was found in the recruitment of P. lineatus between years of high and low discharge, which supports the hypothesis that floods are the main determining factor for recruitment of this species.     

全球主要渔业国家水产科学研究态势及其热点透视

为客观地揭示全球主要渔业国家水产科学的研究态势及其研究热点,以2000—2018年InCites和Web of Science核心合集中文献数据作为统计源,利用文献计量学方法,对其文献的增长趋势、被引情况及期刊分布进行分析,并基于合作网络分析、关键词共现的知识图谱等方法,探究全球水产科学的研究态势及其研究热点。结果显示,在水产科学研究文献的年度发文态势方面,美国的文献数量总体维持在较高水平并呈现动态波动,近年来略有下降趋势;中国大陆的研究文献基本上呈指数增长,并呈稳步上升趋势,至2018年接近美国的发文数量;其他国家都呈现较为平稳的动态波动。载文期刊分布均符合布拉德福提出的文献离散规律,各国载文量排名在前20的期刊大多为国际顶级期刊,其学术上的影响力较大。优势学科领域基本集中在海洋淡水生物学、兽医学、海洋学、动物学、免疫学、湖沼生物学以及生物化学与分子生物学等,但各国侧重点不一致。研究表明,全球主要渔业国家研究热点主要为:①基于生物学参考点的渔业管理与保护研究;②渔业资源评估与管理评价研究;③开展渔业资源的基础生物学研究;④开展基于生态系统的管理措施及政策目标研究等主题。各研究热点间均呈现高度融合的现象,促进了综合性交叉学科的发展。     

东太平洋赤道海域茎柔鱼主要生物学特性比较研究

根据中国远洋鱿钓船于2018年2—4月在东太平洋赤道(110°W～114°W、2°40'S～2°N)作业期间现场取样的1200尾茎柔鱼(Dosidicusgigas)样本进行研究,利用频率分布法分析了2—4月胴长、体重、性腺成熟度和摄食等级的分布,并通过拟合求出了胴长-体重的关系和初次性成熟胴长。根据采样海域的遥感温度,讨论了茎柔鱼不同月份雌雄个体生长的差异。结果显示, 2—4月雄性茎柔鱼优势胴长依次为26～28 cm (19.33%)、30～32 cm (26.46%)、28～30 cm (31.82%),雌性分别为24～26 cm (16.8%)、28～30 cm (24.95%)、26～28 cm (21.79%); 2—4月雌雄茎柔鱼优势体重均依次为400～600 g (28%、20.67%)、600～800 g (29.14%、28.25%)、600～800 g (25.64%、31.82%)。协方差表明3月雌性茎柔鱼与同月雄性茎柔鱼以及2月、4月的雌性茎柔鱼生长模式均存在显著性差异(P_30.01, P_(2-3)0.01,P_(3-4)0.05)。2—4月雌、雄性茎柔鱼摄食等级均以1～2级为主,高摄食等级占比逐月降低。雄性茎柔鱼性腺发育均以Ⅱ期为主,性成熟比例逐月升高,初次性成熟胴长为32.72cm;雌性性腺发育缓慢,各月发育均以Ⅰ期为主,未成熟比例占97%以上,茎柔鱼胴长和体重随性腺等级的提高呈逐级增长状态。综合判断雄性茎柔鱼性成熟比雌性早,性成熟雄性个体或因交配正在离开赤道海域开始向美洲沿岸洄游。     

Increasing the functionalities and accuracy of fisheries electronic monitoring systems

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Spawning patterns provide further evidence for multiple stocks of sardine (Sardinops sagax) off eastern Australia

Previous studies have suggested that sardine, Sardinops sagax, off eastern Australia spawns across its entire range when habitat conditions are suitable. However, recent studies have suggested that separate sub‐populations and spawning groups may occur in the region. Spawning patterns off eastern Australia were investigated using data collected during nine ichthyoplankton surveys conducted between 1997–2015, and adult reproductive data obtained from ad hoc commercial sampling off New South Wales (NSW). The egg surveys covered the known distribution of sardine off eastern Australia and included year‐round sampling in the northern and southern parts of this range. Egg distributions and analysis of gonadosomatic indices identified two spatio‐temporally separate spawning groups; one occurring off southern Queensland to northern NSW during late winter and early spring, and a smaller group off eastern Tasmania to southern NSW during summer. Most eggs were collected from waters 50–90 m deep, with sea surface temperatures of 18–23°C. Additive modelling indicated depth was the most significant factor driving selection of spawning habitat, followed by the interaction of month and latitude. Low egg densities were recorded in waters between 34–37°S, despite conditions within the ranges suitable for spawning. The presence of two spawning groups of sardine off eastern Australia supports recent findings that two sub‐populations occur in the region. Findings of this study will help to optimise the spatio‐temporal extent of future egg surveys and further confirm the need to coordinate future management of each sub‐population among relevant jurisdictions.     

Declining size of adults and juvenile harvest threatens sustainability of a tropical gastropod,Lobatus gigas,fishery

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Tracking interactions: Shifting baseline and fisheries networks in the largest Southwestern Atlantic reef system

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