Coral reef fishes exhibit beneficial phenotypes inside marine protected areas

Abstract

Human fishing effort is size-selective, preferentially removing the largest individuals from harvested stocks. Intensive, size-specific fishing mortality induces directional shifts in phenotypic frequencies towards the predominance of smaller and earlier-maturing individuals, which are among the primary causes of declining fish biomass. Fish that reproduce at smaller size and younger age produce fewer, smaller, and less viable larvae, severely reducing the reproductive capacity of harvested populations. Marine protected areas (MPAs) are extensively utilized in coral reefs for fisheries management, and are thought to mitigate the impacts of size-selective fishing mortality and supplement fished stocks through larval export. However, empirical evidence of disparities in fitness-relevant phenotypes between MPAs and adjacent fished reefs is necessary to validate this assertion. Here, we compare key life-history traits in three coral-reef fishes (Acanthurus nigrofuscus, Ctenochaetus striatus, and Parupeneus multifasciatus) between MPAs and fished reefs in the Philippines. Results of our analyses support previous hypotheses regarding the impacts of MPAs on phenotypic traits. Asymptotic length (Linf) and growth rates (K) differed between conspecifics in MPAs and fished reefs, with protected populations exhibiting phenotypes that are known to confer higher fecundity. Additionally, populations demonstrated increases in length at 50% maturity (L50) inside MPAs compared to adjacent areas, although age at 50% maturity (A50) did not appear to be impacted by MPA establishment. Shifts toward advantageous phenotypes were most common in the oldest and largest MPAs, but occurred in all of the MPAs examined. These results suggest that MPAs may provide protection against the impacts of size-selective harvest on life-history traits in coral-reef fishes.

Improving data deficiencies in length‐weight relationships for fish species around an artificial breakwater and adjacent soft‐bottom at the central coast of Peru

“…Larger body forms in juveniles, as seen on these species, are usually boosted by energy intakes from the environment (e.g. rich reef environment) (Fidler et al., 2018; Rummer & Munday, 2017) as well as development disposal (Barneche, Robertson, White, & Marshall, 2018).…”

“…Extremes values of b, in these cases, might respond to environmental harshness (Welsh, Goatley, & Bellwood, 2013). Fishing pressure additionally influences growth (Audzijonyte & Pecl, 2018;Fidler, Carroll, Rynerson, Matthews, & Turingan, 2018;Frank, Petrie, Leggett, & Boyce, 2018;Heino, Diaz Pauli, & Dieckmann, 2015) and important Peruvian commercial species cannot be rule out of that factor explaining observed low fitness to a linear model and low b values ( Figure S1b).…”

Reviewing the Ecosystem Services, Societal Goods, and Benefits of Marine Protected Areas

“…Since abundance, size or age of target populations increase in MPAs, density-dependent changes in life history traits are also expected within the protected areas or their surroundings (Sánchez-Lizaso et al, 2000;García-Charton et al, 2008). Although some life traits are better documented, such as those on growth or reproduction, other aspects, including behavior or feeding, remain little known (Claudet et al, 2010a;Fidler et al, 2018). Some works highlight the indirect effects that occur as a result of protection.…”

A spatiotemporal comparison of length-at-age in the coral reef fish Acanthurus nigrofuscus between marine reserves and fished reefs

“…Following collection, specimens were euthanized via ice immersion and transported back to a laboratory where standard length (mm) measurements were taken. Sagittal otoliths were removed and prepared for ageing using the protocol described in Fidler et al [17]. Ageing was performed in collaboration with the Fish and Wildlife Research Institute of the Florida Fish and Wildlife Conservation Commission.…”

“…In most fishes, larger body sizes confer greater survival probability, reproductive output, and offspring viability [6,7], while smaller body sizes are highly correlated with the opposite [8][9][10][11][12]. Marine reserves (MRs), which are geographical marine areas that have been designated by a governing authority to strengthen the long-term sustainability of the contained natural resources through the prohibition of exploitative activities [13], should allow for the restoration of historical body-size distributions by (1) eliminating size-selective fishing mortality and (2) resuming ecological drivers that naturally promote larger body sizes [14][15][16][17]. In turn, it is expected that protected populations will subsidize adjacent fished reefs (FRs) through larval seeding and post-settlement spillover [15,[18][19][20].…”