Depth as a fish refuge from spearfishing at Rapa Nui: Flight behaviour in the Pacific rudderfish Kyphosus sandwicensis

Abstract

1. Spearfishing, a common activity among Pacific Islanders, has been described to strongly modify the behaviour of target fish species.2. Rapa Nui (Easter Island), a remote Chilean oceanic island, has suffered a serious decline in its nearshore fish stocks through overfishing.3. In this study, the flight initiation distance (FID) of the Pacific rudderfish Kyphosus sandwicensis was measured at depths normally accessed by free divers and at deeper depths around Rapa Nui and the no-take Motu Motiro Hiva Marine Park (MMHMP).4. The overall FID at MMHMP was significantly shorter compared with that recorded in shallow waters at Rapa Nui, but did not differ from the FIDs recorded in deeper waters at Rapa Nui.5. The biomass of K. sandwicensis did not differ among study sites, but was significantly higher at deeper depths, supporting the hypothesis of depth refuge from fishing at Rapa Nui.6. Based on these findings, spatial and technical management strategies are proposed to help conserve the nearshore fish populations, such as the establishment of no-take zones and the enhancement of regulatory frameworks for coastal fisheries.

Southern California marine protected areas promote bolder fish populations

“…FID has been used to measure the effects of fishing pressures on fish behavior, especially comparing protected and nonprotected areas (Benevides et al, 2018). In studies conducted along the coasts of Barbados, Brazil, and Rapa Nui fish in protected areas had lower FIDs than those in areas where fishing was allowed (Gotanda et al, 2009;Benevides et al, 2018;Petit et al, 2022). FIDs have begun to be used as a metric of the effectiveness of MPAs as they show behavioral characteristics associated with higher fitness.…”

“…To our knowledge, this study is the first to use FID as a metric to evaluate the effectiveness of MPAs in fostering healthy fish populations in such a setting. FID has been used to evaluate the effectiveness of MPAs in Brazil and other countries (Gotanda et al, 2009;Benevides et al, 2018;Petit et al, 2022). It represents a tool to increase the scope of management strategies for protected areas in California.…”