Does Herbivorous Fish Protection Really Improve Coral Reef Resilience? A Case Study from New Caledonia (South Pacific) (original) (raw)
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In response to concerns about declining coral cover and recurring macroalgal blooms, in 2009 the State of Hawaii established the Kahekili Herbivore Fisheries Management Area (KHFMA). Within the KHFMA, herbivorous fishes and sea urchins are protected, but other fishing is allowed. As part of a multi-agency monitoring effort, we conducted surveys at KHFMA and comparison sites around Maui starting 19 months before closure, and over the six years since implementation of herbivore protection. Mean parrotfish and surgeonfish bio-mass both increased within the KHFMA (by 139% [95%QR (quantile range): 98–181%] and 28% [95%QR: 3–52%] respectively). Most of those gains were of small-to-medium sized species , whereas large-bodied species have not recovered, likely due to low levels of poaching on what are preferred fishery targets in Hawaii. Nevertheless, coincident with greater biomass of herbivores within the KHFMA, cover of crustose coralline algae (CCA) has increased from ~2% before closure to ~ 15% in 2015, and macroalgal cover has remained low throughout the monitoring period. Strong evidence that changes in the KHFMA were a consequence of herbi-vore management are that (i) there were no changes in biomass of unprotected fish families within the KHFMA; and that (ii) there were no similar changes in parrotfish or CCA at comparison sites around Maui. It is not yet clear how effective herbivore protection might eventually be for the KHFMA's ultimate goal of coral recovery. Coral cover declined over the first few years of surveys–from 39.6% (SE 1.4%) in 2008, to 32.9% (SE 0.8%) in 2012, with almost all of that loss occurring by 2010 (1 year after closure), i.e. before meaningful herbivore recovery had occurred. Coral cover subsequently stabilized and may have slightly increased from 2012 through early 2015. However, a region-wide bleaching event in 2015 had already led to some coral mortality by the time surveys were conducted in late 2015, at which time cover had dropped back to levels recorded in the KHFMA in 2012.
PLOS ONE, 2021
Marine Protected Areas (MPAs) help replenish fish assemblages, though different trophic levels may show diverse recovery patterns. Long-term protection is required to achieve total recovery but poaching events may prevent the achievement of full carrying capacity. Here, we have analysed the effect of long-term protection on the entire reef fish community and the different trophic levels in the Cabo de Palos-Islas Hormigas MPA (SE Spain; SW Mediterranean Sea) in order to assess their recovery patterns after 23 years of protection. We compared the values for carrying capacity obtained with the maximum values achieved at regional scale, and we assessed the effect of a reduction in the surveillance over a few years, during which poaching events increased, on the recovery patterns. We found that, overall, biomass of fishes increased with time while density diminished. In particular, piscivorous and macro-invertivore fish increased while the other trophic groups remained constant or decli...
ICES Journal of Marine Science, 2008
Considering multiple-species attributes to understand better the effects of successive changes in protection status on a coral reef fish assemblage.-ICES Journal of Marine Science, 66: 170-179. The response of fish assemblages to changes in protection status is a major issue for both biodiversity conservation and fishery management. In New Caledonia, the Aboré reef marine reserve harbours more than 500 fish species, and has been subjected to changes in protection status since 1988. The present study investigates the impact of these changes on a wide subset of species (213), based on underwater visual counts collected before the opening and after the closure to fishing of this marine protected area (MPA). We analysed the spatial and temporal variability in fish assemblage attributable to protection status, explicitly considering habitat. To understand the successive responses of fish assemblage to fishing and protection, the assessment models included four criteria defining species groups that partition the fish assemblage: trophic regime, adult size, mobility, and interest for fishing. We could therefore identify the negative impact of opening the MPA to fishing on piscivores and highly mobile species. Surprisingly, target species were not affected more than non-target species. Model results were used to identify species groups that respond to fishing and protection. These results utilize fisheries-related criteria to provide new insight into the response of fish assemblages to protection from the perspective of MPA monitoring.
Coral Reefs, 2015
Natural fluctuations in the abundance and length of targeted fish are often disrupted by acute environmental changes and anthropogenic impacts, particularly fishing pressure. Long-term assessments of targeted fish populations inside and outside areas closed to fishing are often necessary to elucidate these effects, yet few of these studies extend over long time periods. We assessed trends in the abundance and length of six targeted fish species in areas open and closed to fishing on seven occasions spanning a 9-year period (2005)(2006)(2007)(2008)(2009)(2010) and 2013) at the Houtman Abrolhos Islands, Western Australia. Shallow (8-12 m) and deep (22-26 m) coral-dominated reef sites were sampled across four geographically separated island groups using baited remote underwater stereo-video (stereo-BRUV). Between 2005 and 2010, populations of Lethrinus miniatus, Lethrinus nebulosus, Plectropomus leopardus, and Chrysophrys auratus became increasingly dominated by larger individuals, potentially indicative of an ageing population. Between 2010 and 2013, however, there was a significant increase in the proportion of smaller L. miniatus, L.
Reef Fishes at All Trophic Levels Respond Positively to Effective Marine Protected Areas
PloS one, 2015
Marine Protected Areas (MPAs) offer a unique opportunity to test the assumption that fishing pressure affects some trophic groups more than others. Removal of larger predators through fishing is often suggested to have positive flow-on effects for some lower trophic groups, in which case protection from fishing should result in suppression of lower trophic groups as predator populations recover. We tested this by assessing differences in the trophic structure of reef fish communities associated with 79 MPAs and open-access sites worldwide, using a standardised quantitative dataset on reef fish community structure. The biomass of all major trophic groups (higher carnivores, benthic carnivores, planktivores and herbivores) was significantly greater (by 40% - 200%) in effective no-take MPAs relative to fished open-access areas. This effect was most pronounced for individuals in large size classes, but with no size class of any trophic group showing signs of depressed biomass in MPAs, a...
Aacl Bioflux, 2020
The issue of coral reef resilience is important in this era of climate change and herbivorous fish is one of the key resilience indicators of coral reef ecosystems. This study is a baseline study that aims to assess functional diversity and biomass of herbivorous fish as indicators of resilience potential of coral reef ecosystems in Doreri Bay, Manokwari Regency. Belt transect method was applied in collecting fish species data, number, and length of fish. The functional diversity of herbivorous fish groups was calculated as the number of functional groups present at each observation site. The average length of the fish size class was applied to calculate biomass using the length-weight relationship formula (L-W), which is W = a × L b , where a and b are the parameter values for each species obtained from FishBase. Biomass was calculated as an estimate of the total weight of herbivorous fishes, divided by the area covered by transects, then converted to units of grams per square meter (g m-2). To obtain a composite value from both indicators at each site, the normalization process of the values of each indicator was carried out, then the values of both were averaged. The results showed that herbivorous fish in Doreri Bay consisted of 3 functional groups, namely grazers/detritivores, small excavators/scrapers, and browsers. The grazer/detritivore group was found at 29 sites, scraper/small excavator at 20 sites and browsers at only 12 sites out of a total of 30 observation sites. Biomass values are generally relatively low, ranging from 0.85 to 494.12 g m-2 and the average biomass ranging from 0.42 to 54.90 g m-2. The highest biomass values are found in the southwest of Lemon Island, in the southern reef flat, and south of Lemon Island. In contrast, the lowest biomass was found in the east and northeast of Lemon Island, as well as the northern reef flat. The results of this study suggest that long-term monitoring programs need to be designed to provide long-term trend information from herbivorous fish populations and other important factors in maintaining coral reef resilience.
No-take areas, herbivory and coral reef resilience
Trends in ecology & …, 2007
Coral reefs worldwide are under threat from various anthropogenic factors, including overfishing and pollution. A new study by Mumby et al. highlights the trophic relationships between humans, carnivorous and herbivorous fishes, and the potential role of no-take areas in maintaining vulnerable coral reef ecosystems. No-take areas, where fishing is prohibited, are vital tools for managing food webs, ecosystem function and the resilience of reefs, in a seascape setting that extends far beyond the boundaries of the reefs themselves.
Ecological Indicators, 2014
Many Pacific countries face socio-economic changes, resulting in an increase in fishing pressure on reef fish resources. In coral reef environments, examining the ecological effects of fishing on fish assemblages is generally hampered by the lack of data for both in situ assemblages and fishing activities, and by the difficulty to account for natural variations in assemblages. The responses of fish assemblages to moderate fishing pressure were investigated in two sites of New Caledonia (South Pacific). Habitat structures and fish assemblages were described through in situ multiyear underwater visual surveys to account for spatial and temporal variability. A recent quantification of fishing catches and efforts allowed defining spatial gradients of fishing pressure. Linear models were used to test fishing effects on species richness, density, biomass, length and trophic structure of the whole assemblage, large species, target species, and different ecotrophic guilds. A significant decrease in most metrics was detected when fishing pressure increased. The results obtained for all-species fish metrics were confirmed for target species, large species, carnivores and corallivores trophic guilds and large individuals. This functional modelling approach accounted for the natural variability of local coral reef systems and allowed detecting effects of fishing, although fishing pressure was low to moderate in the surveyed sites. Our results suggest that further modelling development, including control sites, would allow precautionary indicators and strategies to be defined for the monitoring and management of reef fish resources.
Social-ecological vulnerability of coral reef fisheries to climatic shocks
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