Exploitation promotes earlier sex change in a protandrous patellid limpet, Patella aspera Röding, 1798

Abstract

Exploitation of organisms can prompt the reduction in the number and size of target populations consequently affecting reproductive output and replenishment. Here, we investigated the effects of exploitation on the population structure of a protandrous patellid limpet, Patella aspera, an overexploited Macaronesian endemic. Timed dives were used to collect animals across eleven islands of Macaronesia. Individuals were inspected for sex, size, and gonad stage. Using catch effort (time per person) per island coastal perimeter as a surrogate for exploitation intensity, we found that limpet abundance (CPUE) and mean size tended to decrease with exploitation intensity. When considering the sex of animals separately, the size of the largest male, but not females, decreased with exploitation. In contrast, the size of the smallest male remained relatively consistent, whereas the size of the smallest female decreased significantly with exploitation. As exploitation is mostly targeting larger individuals, results suggest that males are compensating the removal of larger females, by undergoing sex change at smaller and presumably earlier sizes. These results have wider implications for the conservation of P. aspera, as a reduction in female size will likely affect the numbers of oocytes produced, hence fecundity. Regulations promoting the protection of the larger‐sized animals should be enforced to safeguard the replenishment of the population.

The protection effects of marine protected areas on exploited molluscs from an oceanic archipelago

“…The removal of organisms for food, bait, aquariums, and shell collection for decorative purposes are human activities that most affect the mollusc populations in coastal zones (Ramírez, Tuya, & Haroun, ), resulting in direct and indirect disturbance of intertidal populations (Addessi, ; Kingsford, Underwood, & Kennelly, ; Lindberg, Estes, & Warheit, ). These disturbances essentially focus on the abundance, size structure, and alterations on the reproductive output and replenishment of the exploited populations as a result of the size‐selective nature of harvesting (Kido & Murray, ; Lindberg et al, ; Martins et al, ; Riera et al, ; Sousa et al, ). Larger specimens are the more attractive, visible, and prone to be caught, adding to their higher commercial value (Kido & Murray, ; Lindberg et al, ; Ramírez et al, ).…”

Disentangling the genetic and morphological structure of Patella candei complex in Macaronesia (NE Atlantic)

“…In most islands, heavy exploitation has led to dramatic decreases in limpet abundances with current populations showing clear signs of over‐exploitation (Martins, Jenkins, Hawkins, Neto, & Thompson, ; Martins et al. ). Because limpet's grazing activity acts as a key process in shaping the structure and functioning of rocky shore communities (Hawkins & Hartnoll, ), the chronic removal of limpets has led to an upward extension of turf‐forming algae (see Boaventura et al., ; Martins, Thompson, Neto, Hawkins, & Jenkins, ).…”

“…Patellid limpets inhabiting these archipelagos are considered a valuable resource and have been intensively exploited presumably since islands were first colonized (Côrte-Real, Hawkins, & Thorpe, 1996;Hawkins, Côrte-Real, Pannacciulli, Weber, & Bishop, 2000;Santos, Hawkins, Monteiro, Alves, & Isidro, 1995). In most islands, heavy exploitation has led to dramatic decreases in limpet abundances with current populations showing clear signs of over-exploitation (Martins, Jenkins, Hawkins, Neto, & Thompson, 2008;Martins et al 2017). Because limpet's grazing activity acts as a key process in shaping the structure and functioning of rocky shore communities (Hawkins & Hartnoll, 1983), the chronic removal of limpets has led to an upward extension of turf-forming algae (see Boaventura et al, 2002;.…”

Editorial: Ecological processes are not bound by borders: Implications for marine conservation in a post‐Brexit world

“…In addition to pure research, progress on conservation has been facilitated. I have been involved in much work in the Azores (Hawkins, Burnay, Neto, Tristao da Cunha, & Frias Martins, ; Martins, Santos, Hawkins, & Nash, ; Santos, Hawkins, Monteiro, Alves, & Isidro, ) on the establishment and efficacy of Marine Protected Areas (MPAs), especially in protecting heavily exploited limpets (Martins, Thompson, Neto, Hawkins, & Jenkins, ) at risk from overexploitation, particularly protandric species (Borges, Hawkins, Crowe, & Doncaster, ; Martins et al, ). The consequences of such overexploitation for community structure has also been shown (Martins et al, , ; Borges, Hawkins, Doncaster, & Crowe, ).…”