bs_bs_banner Animal Conservation. Print ISSN 1367-9430 Changes in the spear fishery of herbivores associated with closed grouper season in Palau, Micronesia S. Bejarano Chavarro1, P. J. Mumby1 & Y. Golbuu2 1 Marine Spatial Ecology Lab, University of Queensland, St Lucia Campus, Brisbane, Qld, Australia 2 Palau International Coral Reef Center, Koror, Palau Keywords Abstract coral reefs; herbivores; spearfishing; Micronesia; Palau; seasonal closures. Several species of coral reef herbivorous fish and groupers (Serranidae) are among the main targets of Micronesian spearfishers. Since 1994, a closed season (April– Correspondence July) protects spawning aggregations of five grouper species in Palau, and, Sonia Bejarano Chavarro, Central Caribbean although this regulation may affect fishers targeting behaviour towards herbivores Marine Institute, Little Cayman Research and increase their catch levels, the extent of these effects was previously unknown. Centre, North Coast Road, P.O. Box 37, This study conducted market surveys and interviews to examine if the closed Little Cayman KY3-2501, Cayman Islands. grouper season in 2009 had any effect on herbivore spearfishing catches, or caused Phone: (345) 948 1094 changes in the targeting behaviour of fishers. Catch volumes of the most desirable Email: [email protected] herbivores were unaffected by the grouper season, but the catch per unit effort of herbivores regularly caught opportunistically (i.e. if seen) or avoided raised by 45% Editor: Trevor Branch during the grouper closure. The size composition of the catch of the bluespine Associate Editor: Olaf Jensen unicornfish Naso unicornis during the grouper closure was significantly skewed to smaller sized fish due to the high proportion of immature individuals. Further Received 21 June 2012; accepted 10 June investigation is required to clarify whether this pattern emerged because fishers 2013 had relaxed size selectivity during the closure or due to a paucity of adults in July. Fifty-seven per cent of the interviewed fishers indicated that while groupers would doi:10.1111/acv.12066 be their first choice during open season, N. unicornis would become their preferred target during the closure, and that other herbivores were also more likely to be targeted. This study took an important step in identifying a factor driving short and acute changes in the herbivore catch composition. Further efforts should be directed to quantify the ecological implications of the observed changes and determine if these are aggravated by the life-history traits or functional roles of the focal species. Relaxed species selectivity might emerge elsewhere, if inherently selective fishing methods are used and highly prized targets are temporarily or permanently banned, or overfished to critical levels. Such implications should be considered when assessing the sustainability of local fisheries. Introduction Friedlander, 1998; Graham & Idechong, 1998; Joseph, 2006; Bavnick et al., 2008). However, the effects of these restric- Artisanal fishing is practised as a primary source of food tions on the behaviour of fishers and the fishing pressure and economic income in many tropical coasts and develop- received by alternative species have rarely been investigated. ing nations around the world (Jennings & Polunin, 1996). In It is possible that fishers respond to restricted access to the tropical Pacific, spearfishing is a relatively affordable profitable species by switching to alternative targets. Such a and therefore widely distributed fishing method that focuses response is especially likely for fisheries that are highly selec- on exploiting coral reef fish (Dalzell, Adams & Polunin, tive with respect to species and size, such as spear fisheries 1996). With growing human populations leading to an (Frisch et al., 2008; Passley, Aiken & Perry, 2010). increased fishing intensity, several types of conservation Although it could be argued that any effect of a short- measures (e.g. gear restrictions, size limits, catch quotas and term closure on the catch of alternative species will only be seasonal closures) have been implemented to manage coral temporary, it might repeat every year, for as long as the reef fisheries (Cinner et al., 2006). Seasonal closures are closure remains effective, thus carrying a cumulative impact. among the most widely used fishing regulations, established Therefore, the implications of seasonal closures need to be to protect populations of commercially important species investigated and considered when assessing the sustainabil- during periods of reproduction (Johannes, 1978b; Beets & ity of local fisheries. Moreover, the changes in fishing Animal Conservation 17 (2014) 133–143 © 2013 The Zoological Society of London 133 Spear fishery of herbivores during closed grouper season S. Bejarano Chavarro, P. J. Mumby and Y. Golbuu behaviour in response to seasonal restrictions on commer- cially important species might give insight into how fishers would respond to population depletions of the same. In Palau (Micronesia), as in several areas across the tropi- cal Pacific, both groupers (Serranidae) and herbivores (i.e. parrotfishes, Scaridae; unicornfishes and surgeonfishes, Acanthuridae; rabbitfishes, Siganidae) are among the main targets of spearfishers (Dalzell et al., 1996; Rhodes & Tupper, 2007). Groupers are especially vulnerable to overfishing because of their slow growth, large size of matu- rity, and because they form spawning aggregations at pre- dictable locations and times (Johannes, 1981; Johannes et al., 1999). The loss of important grouper spawning aggre- gations in Palau in both the 1970s and the 1990s (Johannes et al., 1999) led to the establishment of a seasonal closure through the 1994 Marine Protection Act. Today, the law prohibits the possession and any form of commerce of five species of groupers, namely Epinephelus fuscoguttatus, E. polyphekadion, Plectropomus areolatus, P. laevis and P. leopardus, during the summer months of April through July, to protect them during their peak spawning aggrega- tion period. It is reasonable to expect an increase in spearfishing pres- sure on herbivorous fish during the months of the grouper closure. In fact, this occurred in Pohnpei (Rhodes & Tupper, 2007). Collectively, herbivores provide the founda- tion for the grazing function in most Pacific reefs (Hoey & Bellwood, 2008), and species that fulfil particular functional roles within the guild (e.g. macroalgal browsing) are required to reverse the macroalgal dominance often estab- lished after disturbance (Hoey & Bellwood, 2009). As exploiting herbivores may compromise ecosystem function even before stocks are considered overfished (Mumby et al., 2012; Bejarano et al., in press), it is important to quantify the extent to which the grouper restriction affects herbivore catch volume and composition. In this study, we hypoth- esized that during the grouper closure, the catch of herbi- vores would increase in volume and would contain a higher proportion of small-bodied – generally undesirable – species that may contribute to the fishers’ profit. We tested this hypothesis by examining the differences in herbivore land- ings in Palau when the catch of groupers was restricted and when it was permitted. The effect of the grouper closure on the targeting behaviour of spearfishers was assessed through Figure 1 Map of the study area, Palau (Micronesia), indicating (with a individual interviews. star) the location of the surveyed market in Koror. Materials and methods Dalzell, 1994). As a result, ordinances have been enacted that have banned scuba spearfishing, have regulated Study area minimum mesh size, have imposed season closures The Republic of Palau, with a population of 20 956 (United (Johannes, 1991) and have banned the harvest of Nations’ estimate 2011), is located 741 km east of the Phil- Bolbometopon muricatum permanently (Anonymous, 2007). ippines and 1300 km south-west of Guam (Fig. 1). Palau Eighty-seven per cent of Palauan households currently have has over 500 km2 of reefs, including a 144-km barrier along at least one member fishing for subsistence, for sale or both the West Coast, and a system of 10 marine-protected areas (Fitzpatrick & Donaldson, 2007). According to the latest spanning various reef habitats (Golbuu et al., 2005). South Pacific Forum Fisheries Agency report (Nichols, Palauan fishers have been concerned over diminishing 1991), seafood used to be landed mainly at the principal fish stocks of herbivores since the mid-1970s (Kitalong & market in Koror, but also at other five sites distributed 134 Animal Conservation 17 (2014) 133–143 © 2013 The Zoological Society of London S. Bejarano Chavarro, P. J. Mumby and Y. Golbuu Spear fishery of herbivores during closed grouper season across smaller villages. In 2009, the main fish market in Table 1 Commercially important (non-herbivore) species targeted by Koror remained the only active landing site where reef fish spearfishers in Palau, including the groupers protected by the were marketed daily. Being the main supplier of reef fish for April–July closure. Photocards of the species marked with an ‘×’in locals, restaurants and hotels, this market was the focus of the left column were presented to fishers (along with the favourite our field surveys (Fig. 1). herbivores) to assess their targeting behaviour during open grouper season. Photocards of all species (except the protected groupers) were presented to fishers to assess their change in preferences Field surveys during closed grouper season (right column) Open grouper Grouper Market-based