东、黄海2000年冬季底层鱼类群落结构及其多样性

根据2000年12月～2001年1月东、黄海冬季底层鱼类资源调查资料,分析了该海域的鱼类群落结构。本次调查共捕获鱼类4716.72kg,395796尾,138种。其中,暖水种(WW)居第1位,有81种,占60.00%;暖温种(WT)次之,有53种,占39.26%;冷温种(CT)最少,只有1种,占0.74%。全调查海域的优势种(相对重要性指数QIRI大于500)有5种:带鱼、黄鲫、发光鲷、小黄鱼和鳀;与历史资料相比,优势种个体变小、有被小型鱼类更替的趋势。以质量计算的多样性指数(种类丰富度指数D,Shannon-Wiener多样度指数H′W,种类均匀度指数J′W)呈现由北至南逐渐递增的趋势,而以尾数计算的多样性指数(H′N,J′N)呈现东海北部最高,东海中部次之,黄海南部最低的趋势。生物多样性指数中除种类丰富度指数(D)与水深、海水表温、表层盐度都呈显著性正相关外,而其它生物多样性指数与前述3种环境因子之间的相关性都不显著。单因素方差分析表明,东海北部和中部渔获组成和生物多样性指数都无显著性差别。     

厦门东海域鱼类的群落结构及种类多样性研究

2003年7月至2006年6月对厦门东部海域用定置网和流刺网渔获鱼类进行周年逐月采样分析.结果表明,该海域鱼类至少有287种,录属于21目87科164属,以鲈形目最多,有151种,占总种数的52.6%.渔获物组成以近岸小型鱼类为主,底层鱼类和中下层鱼类合计有235种,占81.88%;中上层鱼类仅52种,占18.12%.鱼类的亚热带动物区系特征明显,暖水性种类达221种,占77%,暖温性种类66种,占23%,未出现冷温性种类及冷水性种类.鱼类种类存在明显的季节更替现象,月更替率大多在30%以上,最高达72.1%.定置网渔获鱼类年平均数量为277尾·网-1,年平均产量为1.93kg·网-1,平均数量和平均产量均以夏季大于秋季大于春季大于冬季;月平均数量和月平均产量均以8月最高,分别为700尾·网-1和5.0kg·网-1,2月最低,分别仅为55尾·网-1和0.38kg·网-1.种类丰度及数量变化与海域水温变化总体呈正相关关系.Shannon-Wiener种类多样性指数的月变化在1.555-4.337之间,多数月份的指数值在3以上,多样性水平较高.渔获鱼类中经济种类占比例较大,但绝大多数个体都比较小,年平均尾重仅6.97g.根据营养动态法估算潜在资源量为1 133.30t年-1,目前厦门东海域鱼类总渔获量已超过最大可捕量一倍以上,应加强资源的管理和保护.     

长山列岛邻近海域鱼类群落功能多样性的季节和空间变化

为查明黄、渤海生态交错带长山列岛邻近海域鱼类功能多样性的时空变化,根据2016−2017年在长山列岛邻近海域开展的鱼类生物资源和环境因子的调查数据,结合食性、营养级、洄游类型、适温性、恢复力和鱼卵类型等13种功能性状,应用群落特征加权平均数指数、功能多样性指数和Spearman秩相关分析等方法,研究了该海域鱼类功能多样性的季节变化、空间格局及其与环境因子的关系。结果表明,春、冬季的优势类群为端位或上位口、生长系数较低、脆弱性较高、恢复力较低、定居或短距离洄游的平扁形、暖温性底层鱼类,夏、秋季表现出更多的功能性状,例如长距离洄游、栖息位置处于中上层、体型为侧扁形和纺锤形等;夏、秋季的功能丰富度指数显著高于春、冬季,功能均匀度指数在春季最高,功能离散度指数在秋季最低且显著低于其他季节;春季功能均匀度指数和春、秋季功能离散度指数均表现出西高东低的分布趋势,夏、冬季的功能丰富度指数和秋季的功能均匀度指数均表现出东高西低的分布趋势;功能多样性指数与环境因子具有一定的相关性。长山列岛邻近海域作为黄、渤海生态交错带,鱼类洄游引起优势功能性状和功能多样性呈现出一定的季节变化,环境因子的变化使得功能多样性的空间格局表现出复杂性、异质性的特点。     

东海、黄海鱼类群落结构的季节变化研究

根据2000年春(4月)、夏(6月)、秋(9月)、冬(12月)四季东海、黄海底拖网鱼类资源调查资料,分析了该海域的鱼类群落结构的四季变化特征.四季全部调查海域中出现的优势鱼种有8种:带鱼、小黄鱼、黄鲫、发光鲷、细条天竺鲷、鳀、鳄齿鱼和刺鲳,其中带鱼和小黄鱼是常年优势种.鱼种季节迁移变化以黄海南部波动最大,东海中部相对较为稳定,东海北部稳定性介于两者之间.生物多样性指数中丰富度指数(D)和Shannon-Wiener多样度指数(H')变化趋势一致,在春、夏两季3个区域相差不大,而在秋、冬两季黄海南部与东海北部和中部有明显分异;种类均匀度指数(J')在四季节3个区域之间相差不大.在暖季(夏、秋)南部鱼类呈向北迁移,而在冷季(冬、春)北部的鱼类有向南迁移的趋势.     

捕捞和气候变化在南海北部湾口鱼类长期种类演替和种群动态的作用

捕捞压力在改变南海鱼类种类演替和生物量波动方面所起的作用大于气候和环境因素是一个普遍的、有争议的假设。根据1959~2010年南海北部北部湾口底拖网的调查数据,报告了该海域鱼类种类组成、优势类群的丰度比例、生物量的季节和年际变化。建立了鱼类生物量与捕捞压力和气候变化外部因素之间的广义加性模型。结果表明,捕捞压力驱动底层渔业资源急剧下降的主要因素,并随着时间的推移,高值鱼类被低值鱼类所取代。1993年和1998年期间鱼类生物量的突然减少与同期厄尔尼诺事件相对应,气候变化可能是渔业拖网捕捞中中上层鱼类比例变化的主要驱动因素。为了更好地了解鱼类群落动态,需要区分捕捞压力和环境驱动因素对不同生活史策略鱼类物种的影响。     

Spatio‐temporal variations in demersal fish assemblages and diversity in the northern Gulf of St. Lawrence (Canada)

Species diversity is generally considered one of the key factors of ecosystem resilience in response to anthropogenic pressures, including fishing. In this context, the spatial and temporal changes in demersal fish assemblages and species diversity were investigated in the northern Gulf of St. Lawrence (Canada), over a 20‐year period (1990–2010). Data were obtained from the summer research survey conducted by the Department of Fisheries and Oceans, and include commercial and non‐commercial species. The study covers the period of groundfish fishery collapse, the moratorium period, and the post‐moratorium period, and reflects various modifications in management. Multivariate statistical methods revealed two communities. A coastal community corresponds to strata located above 200 m depth and a deeper community located in the deep channels. Interannual differences in the composition of fish assemblages were observed and are mainly due to the changes in the relative biomass of some dominant species. Three diversity indices (Shannon–Wiener, Simpson's Index of Diversity and Motomura's constant) indicate a slight but significant increase of the diversity over time. This trend is due to the increase of the relative biomass of low‐rank species, which may have been favoured by the prohibition of groundfish trawling after 1997 in that region. The geographical distribution of the Shannon–Wiener index also shows temporal dynamics reflecting the biomass distribution of dominant demersal species.     

Spatiotemporal distributions and environmental drivers of diversity and community structure of nosZ-type denitrifiers and anammox bacteria in sediments of the Bohai Sea and North Yellow Sea,China

Denitrification and anammox processes are major nitrogen removal processes in coastal ecosystems. However, the spatiotemporal dynamics and driving factors of the diversity and community structure of involved functional bacteria have not been well illustrated in coastal environments, especially in human-dominated ecosystems. In this study, we investigated the distributions of denitrifiers and anammox bacteria in the eutrophic Bohai Sea and the northern Yellow Sea of China in May and November of 2012 by constructing clone libraries employing nosZ and 16S rRNA gene biomarkers. The diversity of nosZ-denitrifier was much higher at the coastal sites compared with the central sites, but not significant among basins or seasons. Alphaproteobacteria were predominant and prevalent in the sediments, whereas Betaproteobacteria primarily occurred at the site near the Huanghe (Yellow) River estuary. Anammox bacteria Candidatus Scalindua was predominant in the sediments, and besides, Candidatus Brocadia and Candidatus Kuenenia were also detected at the site near the Huanghe River estuary that received strong riverine and anthropogenic impacts. Salinity was the most important in structuring communities of nosZ-denitrifier and anammox bacteria. Additionally, anthropogenic perturbations (e.g. nitrogen overloading and consequent high primary productivity, and heavy metal discharges) contributed significantly to shaping community structures of denitrifier and anammox bacteria, suggesting that anthropogenic activities would influence and even change the ecological function of coastal ecosystems.