Abstract
Sea urchin harvesting has rapidly expanded in the last decades. Since many sea urchin species play important ecological role, large-scale commercial sea urchin fisheries can have complex effects on benthic communities. In many temperate regions, overharvesting has compromised marine ecosystems to such an extent that reintroduction of sea urchins raised in captivity may be a valid solution for the enhancement of depleted marine wild populations. In some regions of the Mediterranean Sea, improving the growth efficiency of captive sea urchin Paracentrotus lividus to be reintroduced has become a widespread practice. However, no study has yet considered the potential behavioural effects of raising sea urchins in captivity when they are introduced in the natural environment. This study provides information about the behavioural effects of captivity on P. lividus in terms of locomotion performance, a trait that can be fundamental for responding to predators and for relocation after environmental disturbances such as currents and waves. Movements of captive-born and wild sea urchins were video-recorded and compared in (i) total exposure to external cues, (ii) partial exposure to external cues and (iii) absence of external cues. Latency of locomotion, average speed and average velocity of sea urchins showed significant differences with respect to the level of exposure and their origin (i.e. wild vs. captive-born). Our results demonstrate that captive-born sea urchins in the wild showed long latency and slower locomotor performance when compared to wild sea urchins. Conversely, the straightness-of-path and locomotion direction of captive-born and wild sea urchins were similar in natural settings. Our results therefore suggest that captive-born sea urchins suffer the negative effects of captivity when introduced in a natural environment. Understanding the factors that decrease the performance of sea urchin will be important for developing procedures aimed at minimizing the negative effect of captivity before release into the wild.
Highlights
The overexploitation of species involved in the typical tritrophic interaction ‘fish-sea urchins-macrophyte’ is one of the clearest examples reported for coastal ecosystems of temperate regions (Sala et al, 1998; Loi et al, 2017)
Overfishing is known to have led to the uncontrolled proliferation of herbivore sea urchins, such as the functional key species Paracentrotus lividus in Mediterranean Sea, with dramatic consequences on benthic communities (McClanahan and by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited
The aim of the current study is to evaluate potential behavioural malfunctions and locomotor performance in captive-born P. lividus as a first step towards evaluating their suitability for reintroduction into the wild
Summary
The overexploitation of species involved in the typical tritrophic interaction ‘fish-sea urchins-macrophyte’ is one of the clearest examples reported for coastal ecosystems of temperate regions (Sala et al, 1998; Loi et al, 2017). The consequence of the systematic removal of sea urchin is that community structures have largely changed in several temperate macrophyte ecosystems Large-scale harvesting of sea urchins can determine a rapid development of stands of large brown algae and consequent changes in community composition (Andrew et al, 2002). Along with climate change, overfishing in general has compromised marine ecosystems to such an extent that many traditional conservation targets are out of reach like the case of the Bay of Biscay anchovy (Barange et al, 2010; Rosenberg and Fong, 2013)
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