Investigating spatial aspects of the community-based management of a small-scale artisanal grouper fishery

Fisheries are increasingly understood as complex social-ecological systems (Folke 2006). Fisheries management thus requires an understanding of key processes that underpin both the resource (i.e., fish) and the resource users (i.e., fishers) (Cinner et al. 2009b). These processes invariably operate over differing spatial and temporal scales, and one of the primary challenges facing fisheries management is adequately matching the scale of management institutions and actions to all key social and ecological processes (Cumming et al. 2006). Failure to adequately match the scale of management to these processes can have severe consequences. For example, regional scale management in the northern Altantic was unable to stop the serial depletion of numerous relatively discrete spawning stocks of cod and other groundfish leading to catastrophic and sustained population collapses (Wilson et al. 2013). Such 'problems of fit' have long been a central concern of fisheries management, most notably through Hardin's (1968) 'tragedy of the commons'. For small-scale artisanal fisheries problems of fit are particularly troubling, as key social processes such as patterns of fishing and marine tenure boundaries often operate over very restricted spatial scales (McClanahan et al. 2006). Recognition of this has led to an increasing global proliferation of community-based management of small-scale fisheries (Govan et al. 2006, 2009). However, critics suggest that problems of fit with the spatial scales of key ecological processes may drastically diminish the ability of community-based management to achieve conservation goals (Foale and Manele 2004; Mills et al. 2010). This thesis examines potential problems of fit for community-based management, through the case study of two vulnerable grouper species, Epinephelus polyphekadion and E. fuscoguttatus, targeted within a multi-species artisanal coral reef fishery in Papua New Guinea. Specifically I ask: What are the spatial problems of fit between community-based governance institutions, relatively mobile target fishes, and the fishers that target them within small-scale artisanal fisheries? Many aspects of this study drew upon the local knowledge, advice, and participation of community fishers of Dyual Island, Papua New Guinea. A range of social science and ecological research methods were employed to assess the spatial scales of operation and governance of the local fishery, and key life history processes for the focal species. Local stakeholders were intrinsically involved in the work, with research questions and methods greatly influenced by community input. Data were collected during extended field seasons within the communities of Dyual Island, Papua New Guinea, and by trained local stakeholders throughout the study period. The specific scientific objectives of this study were to (1) determine the spatial patterns of settlement, clan affiliation, access rights, and fishing effort within the local fishery, and the spatial scales of the governance institutions most relevant to its management; (2) detail the key demographic and reproductive characteristics of the two focal species of grouper; (3) examine changes in the spatial distributions of the focal species throughout their post-settlement life histories (i.e., ontogenetic shift); (4) examine the reproductive migrations of populations of the focal species associated with a multi-species transient fish spawning aggregation; and finally (5) investigate the level of spatial fit between community-based governance institutions and these key social and ecological processes. The focal fishery of this study was governed through two complementary systems –Papua New Guinea's relatively recent Westminster governance system and the enduring system of customary ownership which has much older origins. The study region was under the statebased jurisdiction of the Leon Village Planning Committee encompassing approximately 45 km² of shallow sub-tidal and inter-tidal habitat. The customary ownership of this area was divided between three clan groups, with individual tenure over areas of 7 – 19 km². Local inhabitants had access rights across the entire study area, regardless of clan affiliation. However, fishing effort was highly concentrated around human settlements, such that half of fishing effort was concentrated within just 10% of the study area. Both E. polyphekadion and E. fuscoguttatus exhibited relatively typical epinephelid life histories which make them intrinsically vulnerable to overfishing. They had long lifespans (with maximum ages of 22 and 27 yrs, respectively), relatively slow grow rates, and relatively late reproductive maturity. Females of both species reached sexual maturity between 4 – 8 yrs of age. Epinephelus fuscoguttatus reached greater lengths and exhibited faster growth. As such, female E. polyphekadion entered the reproductive population between 278 – 380 mm in length (with 50% mature at 330 mm), whereas female E. fuscoguttatus entered the reproductive population between 370 – 480 mm in length (with 50% mature at 430 mm). These ages and sizes at maturity were used to investigate the habitat requirements of these species throughout their post-settlement life histories. Habitat suitability modelling indicated that ontogenetic shift was similar for both species. Juveniles (i.e., individuals under the age/size at 50% female maturity) were restricted to habitat directly adjacent to land, particularly around mangroves and freshwater inputs. Both species occupied broader ecological niches throughout their post-settlement life histories. Adult (i.e., individuals above the age/size at 50% female maturity) habitat included patch and barrier reef habitats characterised by high live coral cover, as well as the fringing habitat preferred by juveniles. Acoustic telemetry revealed that the fish spawning aggregation currently under community-based management drew E. fuscoguttatus individuals from a 'catchment area' (i.e., the total area inhabited by the entire spawning population throughout the non-spawning season) of at least 16 km². Further analysis however, indicated that reproductive migrations were skewed toward shorter distances. As a result, 30 – 50% of the spawning population resided within the 1-2 km² directly adjacent to the aggregation site throughout the non-spawning season. Finally, I brought together all of the key social and ecological scales considered throughout this thesis, and demonstrated that at western Dyual, community-scale governance institutions presented a good spatial fit to manage the artisanal fishery for these commercially valuable grouper. The ecological processes considered here (ontogenetic shift in habitat suitability and reproductive migration to and from fish spawning aggregations) could be effectively managed at the scale of individual tenure areas. Individual spawning stocks would best be managed at this scale to avoid serial depletions. However, social processes were poorly aligned with tenure areas. Common access to resources and variable patterns of settlement resulted in highly variable fishing effort between tenure areas. Management opportunities within the most heavily fished tenure area were particularly restricted. Thus, the larger scale of community-based governance considered here, encompassing approximately 45 km², provided a better spatial fit with social processes, primarily due to its alignment with stakeholders (i.e., resource users). However, fishing effort varied at extremely fine spatial scales here. This could produce serial depletion of grouper stocks here, even within these spatially restricted management areas. This thesis demonstrates that community-based management institutions can provide a good spatial fit for managing key social and ecological processes that underpinning the persistence of relatively mobile coral reef fisheries. However, nested governance institutions may be required, even at these restricted spatial scales.