Fishery benefits from behavioural modification of fishes in periodically harvested fisheries closures

Abstract

Periodically harvested fisheries closures are widely implemented across the South Pacific as a conservation and fisheries management tool. There is a lack of information on the mechanisms and effectiveness of this management system in meeting fisheries and ecosystem sustainability goals.A before‐after‐control‐impact (BACI) pair design, was used to quantify flight initiation distance (FID), and biomass of two fishery‐target (Acanthuridae and Scaridae) and one non‐target (Chaetodontidae) families in two periodically harvested closures, two no‐take marine reserves, and two open fished areas, prior to and after harvest of the periodically harvested closures. Creel surveys were used to quantify catch per unit effort (CPUE) in open fishing grounds, and during the periodic harvests.Before harvest, FID of targeted families was higher in fished areas than periodically harvested areas. After harvest, Acanthuridae FID in periodically harvested closures increased significantly to beyond the maximum effective range of spearguns. Total biomass of fishes was lower in fished areas than areas under either type of management. Acanthuridae biomass in the periodically harvested closures was similar to fished areas, and lower than in the no‐take reserves. There was no difference post‐harvest for either total or Acanthuridae biomass.CPUE was higher for fishing trips inside the periodically harvested closures than regular fishing activities. Fishes were generally larger in catches from periodically harvested closures, but this was not sufficient to account for the increase in CPUE, particularly of the Acanthuridae, which were significantly more abundant in the harvest catch.When fishes are protected temporarily from fishing, their wariness decreases, which makes them more easily catchable when fishing is reinstated. This study shows that fish behavioural change is an important and overlooked benefit of periodically harvested closures. However, differences in the magnitude of behavioural changes between fishery‐target families may result in contrasting outcomes of periodically harvested management regimes. Copyright © 2013 John Wiley & Sons, Ltd.

Demonstrating multiple benefits from periodically harvested fisheries closures

“…However, we were not able to account for migration/movement of targeted species across PHC boundaries, which differs among target species (Nash, Welsh, Graham, & Bellwood, ) and is, therefore, likely to have contributed to the variability in results across PHCs (Eggleston & Parsons, ). Regardless of the mechanism, greater abundance and biomass of fish in PHCs translated to harvest benefits where fishers removed an average of 29% of the abundance and 49% of the biomass, a result likely due to greater catch efficiency associated with decreased wariness of targeted fishes within PHCs (Feary et al., ; Goetze, Januchowski‐Hartley et al., ; Januchowski‐Hartley et al., ). Therefore, PHCs are a particularly effective fisheries management strategy for increasing short‐term fisheries yields from single harvest events.…”

“…Historically, PHCs were implemented to increase catch efficiency through a decrease in fish wariness, because fishers observed that the behaviour of fish changes during closure, making them easier to catch (Cinner, Marnane, McClanahan, & Almany, ; Feary, Cinner, Graham, & Januchowski‐Hartley, ). More recently an increase in catch efficiency within PHCs has been observed for invertebrates harvested via gleaning (collection during low tide) (Cohen & Alexander, ) and fish through a reduction in wariness to spearfishers (Goetze, Januchowski‐Hartley, et al., ; Januchowski‐Hartley, Cinner, & Graham, ). However, this increased catchability also means that a small amount of fishing effort can effectively remove substantial biomass (Jupiter et al., ).…”

“…Consequently, pulse harvests in PHCs benefit fishers in the short‐term, but potentially increase the likelihood of overharvesting, compromising long‐term conservation and fisheries management objectives (Cohen & Foale, ; Jupiter et al., ). Despite a growing literature on PHCs (Bartlett et al., ; Cinner et al., ; Cohen & Alexander, ; Cohen, Cinner, & Foale, ; Goetze et al., ; Januchowski‐Hartley et al., ; Jupiter et al., ), there is little quantitative work to understand their ability to achieve these short‐ and long‐term fisheries and conservation objectives.…”

Fish wariness is a more sensitive indicator to changes in fishing pressure than abundance, length or biomass

“…Traditional community closures often involve short closure times (i.e., 100 d in Fiji), which may coincide with the time needed to make fish less wary to spearfishers (e.g., Januchowski‐Hartley et al. ), but shorter than the time needed to produce significant increases in abundance, length, or biomass (McClanahan et al. ).…”

“…, Januchowski‐Hartley et al. ). Customary closures have been observed to reduce FID to an extent that is likely to increase catchability for surgeonfish (Acanthuridae) within six months of closure, an effect lost in as little as three days when reopened to fishing (Januchowski‐Hartley et al.…”