Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, Sassari, Italy.
AGRIS Sardegna-Research Service for Fishery Products, Olmedo (SS), Italia.
PLoS One. 2024 Apr 18;19(4):e0301143. doi: 10.1371/journal.pone.0301143. eCollection 2024.
Where sea urchin harvest has been so intense that populations have drastically regressed, concerns have arisen about the effectiveness of harvesting management. According to the theory of phase transition in shallow rocky reefs between vegetated and barren habitats, sea urchin recruitment, a key population structuring process, seems hampered by some stabilizing feedback despite an end to local human harvest of sea urchins. To shed a light on predation effects on sea urchin recruits, a 27-day field experiment was conducted using mega-predator exclusion cages (40x40x40 cm, 1 cm in mesh size) in barren and turf substrates. To facilitate this, 672 recruits (1.1 ± 0.02 cm in size) reared under control conditions were positioned in groups of 42 in each experimental unit (n = 4). Exclusion of mega-predators had a significant effect regardless the substrate, since a higher number of recruits was found under cages both in turf and barren. However, the results showed that in uncaged treatments the size of recruits that survived was larger in turf than in barren, as in the former substrate predation had reduced the abundance of the smallest recruits, highlighting that mega-predator presence affects differently the size of the recruits that had survived depending on the substrate. Overall, these results provide valuable information to address restocking actions of sea urchin populations in overharvested areas, where algal turfs are widespread, and assist studies on habitat stability mechanisms.
在海胆捕捞强度如此之大以至于种群数量急剧减少的地方，人们对捕捞管理的有效性产生了担忧。根据浅岩礁植被和贫瘠生境之间的相变理论，尽管当地已经停止了对海胆的人类捕捞，但海胆的补充（关键的种群结构过程）似乎受到了一些稳定化反馈的阻碍。为了阐明捕食作用对海胆幼体的影响，在贫瘠和草皮基质中使用大型捕食者排除笼（40x40x40 厘米，网眼大小为 1 厘米）进行了为期 27 天的野外实验。为此，在对照条件下饲养了 672 只大小为 1.1 ± 0.02 厘米的幼体，将它们分组放置在每个实验单元（n = 4）的 42 个位置中。无论基质如何，排除大型捕食者都有显著影响，因为在草皮和贫瘠基质中笼内都发现了更多的幼体。然而，结果表明，在无笼处理中，草皮基质中存活的幼体大小大于贫瘠基质，因为在前一种基质中，捕食减少了最小幼体的数量，这表明大型捕食者的存在会根据基质的不同，对存活的幼体大小产生不同的影响。总的来说，这些结果为解决过度捕捞地区海胆种群的重新放养行动提供了有价值的信息，因为在这些地区，藻类草皮广泛存在，并有助于研究栖息地稳定性机制。
