Use of Artemia supplemented with exogenous digestive enzymes as sole live food increased survival and growth during the larviculture of the longsnout seahorse Hippocampus reidi

This study evaluated the effect of exogenous digestive enzymes on the survival, growth performance and morphology of the digestive tract of juveniles of the longsnout seahorse Hippocampus reidi fed exclusively with Artemia and supplemented with five different concentrations of porcine pancreatin (PP) (0, 5, 25, 50 and 75 mg/L from birth until 30 days after release). The results found in the present study clearly show that there was a significant increase in survival and growth as well as substantial changes in the morphology of intestinal villi in seahorses fed exclusively with Artemia supplemented with 75 mg/L PP. Therefore, the use of digestive enzyme supplementation constitutes an important advance for the establishment of a more efficient and practical feeding protocol (exclusive use of Artemia) for juveniles of the longsnout seahorse.     

A conservation trade‐off? Interspecific differences in seahorse responses to experimental changes in fishing effort

• 1. A 2‐year experimental seining programme and underwater visual censuses were undertaken to quantify the direct effects of active demersal fishing on the population structure and relative abundance of two sympatric seahorse species of conservation concern: the European long‐snouted seahorse, Hippocampus guttulatus Cuvier 1829 and the short‐snouted seahorse, Hippocampus hippocampus L. The influence of habitat preference on population‐level responses to changes in habitat structure following a reduction in fishing effort was also investigated.
• 2. It was predicted that the benthic habitat would be more structurally complex after fishing ceased and that seahorse densities would increase in response to reduced fishing mortality. Furthermore, it was predicted that the magnitude of the increase in density would be greater for H. guttulatus than for H. hippocampus, because the former species prefers complex vegetated habitats while the latter species uses sparsely vegetated habitats.
• 3. As predicted, the amount of habitat cover increased significantly when seining ceased, primarily through increases in the abundance of drifting macroalgae and unattached invertebrates. Despite similarities in life histories, the two seahorse species responded differently in terms of magnitude and direction to reduced fishing effort: the abundance of H. guttulatus increased significantly while H. hippocampus decreased in abundance.
• 4. Results suggest that active demersal fishing may influence the magnitude and direction of the responses of benthic marine fishes to exploitation through its impacts on habitat structure. An increase in habitat cover appeared to favour higher densities of H. guttulatus when seining effort was reduced. By contrast, repeated seining, which maintained less complex habitats, appeared to favour greater abundances of H. hippocampus.
• 5. Given differences in habitat preference among benthic marine fishes subject to incidental capture in fisheries, simultaneous attempts to manage populations of sympatric species may require complementary strategies that support the persistence of diverse habitat types.

Copyright © 2006 John Wiley & Sons, Ltd.     

辽宁沿海日本海马线粒体控制区序列变异及其在海龙科鱼类系统分析中的应用

为研究日本海马野生群体的种质资源及遗传多样性状况,实验采用PCR扩增法获得日本海马线粒体DNA的控制区序列片段,同时利用GenBank数据库中已有的14种海龙科鱼类控制区同源序列对其进行序列比较及系统进化分析。结果显示,日本海马控制区序列片段长度为557~558 bp,其A、T、G、C 4种碱基的平均含量分别为34.3%,29.7%,14.1%,21.9%。在控制区序列片段中,共检测到16个多态性核苷酸位点,定义了16种单倍型,其核苷酸多态度和单倍型多态度都较低(π=0.0032±0.0021,h=0.70±0.02)。利用GenBank数据库中已有的海马控制区同源序列,采用邻接法、最大似然法和贝叶斯法构建了分子系统树。结果显示,采用最大似然法和贝叶斯法构建的分子系统树拓扑结构与邻接法构建的分子系统树拓扑结构不完全相同但基本一致,系统进化分析结果与形态分类学的观点一致。研究表明,线粒体DNA控制区序列在海龙科不同阶元间变异较大,适合于海龙科鱼类种间、群体水平的研究以及作为系统进化分析的分子标记。