Natural Resources Institute Finland (Luke), Joensuu, Finland.
Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland.
PLoS One. 2021 Dec 2;16(12):e0260944. doi: 10.1371/journal.pone.0260944. eCollection 2021.
Enrichment of rearing environment with natural elements has been suggested to improve the welfare and post-release survival of cultured fish. We studied the combined effects of shelter structures, periodical water flow and water level changes on pre- and post-release performance of critically endangered landlocked Atlantic salmon (Salmo salar m. sebago). Relative to standard (plain) rearing tanks, provision of enrichment improved fish condition factor and survival during the first year of rearing when most mortality was attributable to parasitic and bacterial infections. The consequent higher density in enriched tanks probably induced greater growth variation and more dorsal fin damages than found in fish of standard tanks. Possibly this was partly due to the applied changes in water level. Experimentally determined smolt migration tendency at age 3 did not differ, on average, between the rearing groups, but enriched-reared fish showed clearly less variation in total movement activity than standard-reared fish. Experimental angling in earthen ponds did not suggest divergent vulnerability between the differentially reared fish at age 3, but decreased condition during the preceding growth season increased vulnerability to fishing. Based on long-term post-stocking tag returns in large-lake fisheries, fish length at release but not rearing method affected the capture rates of fish released at age 2. When released at age 3 the fish grown in enriched environment had a higher risk to be captured with stationary gears and earlier by hook and line gears compared to standard-reared conspecifics. Earlier time of maximal smolt migration activity was associated with an increased risk of being captured. We suggest that environmental enrichment may modulate growth- and behavior-related qualities that indirectly increased the vulnerability to fishing in natural conditions but not in experimental setting. The favorable effects of enrichment on early survival encourages adopting enriched rearing practices in supportive breeding of landlocked salmon.
养殖环境中添加自然元素可提高养殖鱼类的福利和放流后成活率。本研究探讨了遮蔽结构、周期性水流和水位变化对濒危内陆大西洋鲑（Salmo salar m. sebago）放流前和放流后表现的综合影响。与标准（普通）养殖水槽相比，养殖环境得到改善可提高鱼类的养殖成活率和养殖第一年的养殖成活率，因为大多数死亡率归因于寄生虫和细菌感染。在养殖水槽中，由于采用了水位变化，因此可能导致比标准水槽中的鱼类更大的生长变化和更多的背鳍损伤。这可能部分是由于应用的水位变化所致。在 3 龄时，通过实验确定的洄游迁移倾向平均而言，在不同的养殖组之间没有差异，但与标准养殖鱼类相比，养殖环境得到改善的鱼类的总运动活动变化明显较小。在土池塘中进行的实验性钓鱼并没有表明在 3 龄时不同养殖方式的鱼类存在不同的脆弱性，但在生长季节之前的条件下降增加了对捕捞的脆弱性。基于大湖渔业中的长期放流后标签返回数据，放流时的鱼体长度而不是养殖方式影响了 2 龄时放流鱼类的捕捞率。当在 3 龄时释放时，与标准养殖的同种鱼相比，在富养殖环境中生长的鱼在使用固定渔具和更早使用钩钓渔具时，被捕捞的风险更高。最大洄游活动时间越早，被捕捞的风险就越大。我们认为，环境富集可能会调节与生长和行为相关的品质，这些品质会间接增加在自然条件下但不会在实验条件下的捕捞脆弱性。富养殖对早期存活率的有利影响鼓励在支持内陆鲑鱼繁殖的过程中采用富养殖实践。
