Individual study: Disentangling the effects of fishing and environmental forcing on demographic variation in an exploited species
Teck S.J., Lorda J., Shears N.T., Bell T.W., Cornejo-Donoso J., Caselle J.E., Hamilton S.L. & Gaines S.D. (2017) Disentangling the effects of fishing and environmental forcing on demographic variation in an exploited species. Biological Conservation, 209, 488-498
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Designate a Marine Protected Area and prohibit the harvesting of sea urchins
A replicated, site comparison study in 2009–2011 of 30 sites around the Northern Channel Islands, southern California, North Pacific Ocean, USA (Teck et al. 2017) found that, six to 33 years after their designations, marine protected areas prohibiting the harvest of red sea urchin Mesocentrotus franciscanus had bigger adult urchins, higher adult total biomass and reproductive biomass, but similar urchin reproductive indices (ratio of reproductive to total biomasses), compared to sites where urchin harvest was allowed. Adult urchins diameter was 6% bigger inside the marine protected areas compared to outside. Adult total biomass was 16%, and reproductive biomass was 23% greater inside the marine protected areas compared to outside. Once a year in summer between 2009 and 2011, eleven sites within seven marine protected areas and 13 sites outside of marine protected areas were surveyed at 6 m and 13 m depths (143 surveys in total). One marine protected area was designated in 1978, and six in 2003. Despite having different levels of activity restrictions, all areas prohibited the harvest of the red sea urchin. Divers counted all urchins >25 mm test diameter along two 60 m2 transects/site/water depth. Fifteen to 20 urchins >50 mm (test diameter) were collected, measured, and their flesh and reproductive glands weighed. For each are. adult total biomass (using total urchin weight) and reproductive biomass (using urchins reproductive gland weight) were calculated from urchins count and weight data.
(Summarised by Anaëlle Lemasson)