Investigating the Effects of a Closed Season on the Small Pelagics Fishery in the Visayan Sea – Ecological and Managemant Policy Implications

Abstract (abridged):

This thesis applies the Ecosystem Approach to Fisheries Management (EAFM) to assess a closed season for small pelagics in the Visayan Sea, Philippines. The closed season has been a controversial policy, with earlier studies being largely critical of its implementation.  This thesis is an earnest response to the calls for a more holistic assessment of the Visayan Sea fisheries and aims to generate information that can provide guidance in the strategic evaluation and implementation of the closed season for the small pelagics therein. Statistical analytical approaches were first applied to better understand the fisheries trends in the Visayan Sea in relation to seasonally variable local environmental parameters and regional climate-related indices. In general, a combination of below-average SSTs, above-average net primary productivity, moderate rainfall, and above-average wind speeds during the early northeast monsoon provide the optimum conditions for the parent stocks and early developing cohorts, which translate into higher catch abundance in the immediately succeeding couple of years.  The above approach was then expanded to investigate the role and extent of the fishery, inter-specific (trophic) interactions, and changing environmental conditions as drivers of catch and stock abundance in the Visayan Sea. For this purpose, a baseline ecosystem model (Ecopath with Ecosim) of the Visayan Sea was constructed using data from the earliest comprehensive fisheries survey and assessment in the area (1996-1997). The model was then calibrated via time-series fitting to historical catch and abundance data provided by the National Stock Assessment Program (NSAP), and with 2-decades long fishing effort trends and the same local environmental parameters as drivers of the model.  The results suggest that the fisheries and trophic controls are the main factors that have shaped the biomass and catch trends in the Visayan Sea over the past two decades, while the environmental factors all provide explanations for group-specific patterns that cannot be explained by fishing alone. A comparison between the state of the Visayan Sea between the baseline model (1997) and the end simulation (2018) was then performed to identify and assess the significant changes that have occurred. Carrying on with the ecosystem approach, the assessment applied a network analysis and used a suite of biomass-based, catch-based, trophic-based, species-based, and size-based indicators (ECOIND).  In addition, trends in fish and invertebrate catches were translated into monetary values using wholesale price prices to document the direct economic consequence of these changes. After a thorough analysis of the drivers and the system’s response to these drivers, an analysis of the effects of the Visayan Sea closed season for small pelagics was carried out.  The calibrated time-dynamic Visayan Sea Ecosim model was used to hindcast the effects of the closed season along with 9 other hypothetical alternative scenarios representing different configurations of fishing fleets involved (i.e., commercial, municipal, and prohibited operations) and their levels of implementation (i.e., % fishing effort reduction). Based on earlier studies that showed that 60% of operators continue fishing during the designated closed season months, a business-as-usual (BAU) scenario was designed to reflect a 40% reduction in the effort of commercial gears and municipal surface gillnets that primarily target the small pelagic stocks. The 9 other scenarios then reflect various combinations of % effort reduction by the commercial, municipal, and prohibited gears based on actual proposals made during a closed season task force workshop and technical feedbacking seminars in the Visayan Sea.  Biomass-based ecosystem and biodiversity indicators, and fisheries indicators of catch, profits, and livelihoods were used to assess the effects.  Results reveal that the closed season alone and its current level of implementation is insufficient in reducing the fishing pressure on the target small pelagic groups and in improving biodiversity and other ecological indicators.  To maximize these objectives, no less than a 100% compliance by both the commercial and municipal fleets is required, but would entail high fisher displacement during the closed season.  On the other hand, a focused implementation of the policy on the commercial fleets was shown to maximize net profits over time, but with little improvements on the biological and ecological indicators. Finally, a case study of a successful closed season in another Philippine fishing ground (Balayan Bay) is presented to draw out elements of success that can be potentially applied to improve the Visayan Sea closed season implementation.  These elements generally point to multi-sectoral participation in the data-gathering, planning, rule- and decision-making, and in the enforcement of the closed season.  Local knowledge was also utilized to complement the biological information that was generated by scientific studies.  Moreover, programs were set up to address the temporary loss of livelihoods for affected fishers during the closed season.

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