Design for sustainable management of seagrass ecosystems for supporting fisheries in the Spermonde Archipelago, South Sulawesi

Abstract

Seagrasses have been well known as important habitat for various fauna, including numbers of economic important fishes, especially in the nursery stage. Therefore, seagrass ecosystems management is an important part of managing the marine fisheries. Spermonde Archipelago, a hotspot of coral and seagrass, consist of ± 120 small islands and have dense population (most of them depends on subsistence and small scale fisheries), especially in the south east of the archipelago implements an increased pressure to the seagrass ecosystems. The pressure to the ecosystems will affect the fisheries productivity. By knowing the sustainability status of the seagrass ecosystems, it will facilitate an assessment of the effectiveness of fisheries management and it will provide a valuable information to policy makers about the best policy option for the sustainability management of seagrass ecosystems in the future. Based on that, the main goal of this study was to determine the sustainability status of seagrass ecosystems in Barrang Lompo Island (BL) and Kapoposang Island (KP) for supporting fisheries. In order to achieve the main goal, there are three specific objectives were performed, namely 1). to analyze fish community structure in the seagrass beds, 2). to analyze the fishing activities and their status in the seagrass beds, 3). to design the sustainable management of seagrass ecosystems. Fish community structure was analyzed using non-metric multidimensional scaling technique and Bray-Curtis cluster analysis, while the most contributed species to difference of fish community structure was analyzed using SIMPER (similarity of percentages) procedure. All statistics analysis were carried out using PRIMER v6 software. The difference between fish distribution in both seagrass beds was analyzed with t-test and Bonferroni post-test using PRISM v5 software. Fishing activities were analyzed through fisher recognition based on the latest census data from village office and by interviews, observation of fisher’s behaviour during fishing in the seagrass beds, classification of their catches, analysis of maturity size of their catches based on life stage classification using fish maximum length. Status of fishing in the seagrass beds were determined based on FAO-like exploitation status scale and analyzed through measurement of catch per unit effort (CPUE), total catch in one year (Y), natural mortality as weight-dependence of mortality (Mw), estimated biomass in the same year (B), and maximum sustainable yield (MSY). RAPSECS (rapid appraisal technique for evaluating seagrass ecosystems sustainability) analysis using multidimensional scaling (MDS) was applied to analyze the sustainability status of seagrass ecosystems for each dimension (ecology, economic, social, technology, institution). A combination of pairwase comparison and geomean was used to determine the general sustainability status of each seagrass fisheries. Leverage analysis was applied to identify the most influence attributes to the sustainability status of each dimension. Strategy intervention was formulated based on the most influence attributes within each dimension. The results of non-metric multidimensional scaling technique and Bray- Curtis cluster analysis revealed that overall, there were significant differences of fish community structure and distribution pattern in the seagrass beds dominated by Thalassia hemprichii (TH) and Enhalus acoroides (EA). Fish abundance was higher in TH- than in EA-dominated beds, but fish biomass and species richness were lower in TH- than in EA-dominated bed, indicating that there were more smaller fish assemblage in TH site than in EA site, while larger sizes and more variety of fish species utilize EA site. The major contributor fish species to the difference of fish community structure between these two seagrass beds were Apogon bandanensis, Lethrinus harak, A. hoeveni, Liza vaigiensis for fish abundance, and Tylosurus crocodilus, Siganus canaliculatus, A. bandanensis for fish biomass dry weight. More abundance larger fish was found during day time than night time in EA-dominated bed. It indicates that EA site may facilitate foraging efficiency of larger fish during day time because more abundant and higher biomass dry weight (DW) of fishes were found in EA site during day time compare with night time. The higher canopy provided by the seagrass E. acoroides in EA site may also improve the predation efficiency and so that beneficial for some fishes, especially predators, such as Choerodon anchorago, Dyodon histrix, and Saurida gracilis. Abundance and biomass of fish juvenile and adults were comparable in the two seagrasss beds. Meanwhile, abundance of fish subadults was higher in T. hemprichii- than in E. acoroides-dominated beds and vice versa for the subadults biomass. The higher occurrence of juvenile fish than adults in the seagrass beds either dominated by TH or EA indicated that seagrass is an important nursery habitat for various fish spesies. Small fish (0-7.5 cm) more abundance in TH-dominated bed, while more larger fish sizes were found in EA-dominated bed indicating that fish assemblage in the seagass bed dominated by TH was majority small fish (juvenile and/or small, inconspicuous adult fish), however in the seagrass bed dominated by EA harbored larger fishes. The reason is because EA sites, provide higher canopy height and facilitating the improvement of predation efficiency for some larger predators, such as Choerodon anchorago, Dyodon histrix, and Saurida gracilis. Meanwhile, smaller fish (including juvenile and small inconspicuous adult fish) preferred TH site as this site provide lower canopy heights that is not beneficial for predators. The results of fishing activities analysis in the seagrass beds showed that fishing in the seagrass beds, either in BL or in KP, was not a main job and they did fishing in the seagrass beds only when they got rest from their main job. Besides, only certain fisher who did fishing in the seagrass beds. Fishing practices in BL was considered to have more negative impact on seagrass beds than in KP, as the fishers in BL always made trampling and boat anchoring during fishing in the seagrass beds. Most fishes in both islands were captured before maturity, and one of the captured fish family (Dasyatidae) has been considered internationally to be conserved. Total CPUE of seagrass fish in BL was lower than in KP, however, the fishing rate of seagrass fish in both islands were relatively the same and categorized as under exploitation. Multidimensional evaluation results revealed that generally, seagrass fishery of Kapoposang Island is better than of Barrang Lompo Island, mainly on ecological and technological dimensions. “seagrass percent cover”, “catch before maturity”, “limited entry”, “price”, “education level”, environmental knowledge”, “selectivity gear”, “fishing practice”, “education & training”, and “seagrass protection” are the most influence attributes found in both seagrass fisheries. Overall, it was concluded that prioritized strategies for seagrass ecosystems management include institution strengthening, human resource development, and environmental improvement (for BL) and institution strengthening and human resource development (for KP). The recommendations are fishing status in BL and KP should be maintained to the level under-exploitation through strict control and monitoring by fisheries authorization. Additionally, mitigation effort on seagrass beds in the Spermonde Archipelago is important to be made in order to maintain the sustainable function of the seagrass beds, especially in fisheries sectors.

Tujuan utama penelitian ini adalah untuk merancang strategi pengelolaan ekosistem lamun yang berkelanjutan di Pulau Barrang Lompo (BL) dan Kapoposang (KP) untuk mendukung perikanan. Sub tujuan adalah untuk 1). Menganalisis struktur komunitas ikan di padang lamun yang didominasi oleh Thalassia hemprichii (TH) dan Enhalus acoroides (EA), 2). Menganalisis aktivitas penangkapan di padang lamun Pulau Barrang Lompo (BL) dan Kapoposang (KP) dan statusnya, 3). Merancang srategi pengelolaan ekosistem lamun berkelanjutan di BL dan KP. Struktur komunitas ikan dianalisis menggunakan teknik non-metric multidimensional scaling and analisis kelompok Bray-Curtis, spesies ikan yang paling berkontribusi terhadap perbedaan struktur komunitas dianalisis menggunakan prosedur SIMPER (similarity of percentages) menggunakan perangkat lunak PRIMER v6. Aktivitas penangkapan dianalisis melalui hasil observasi perilaku nelayan selama penangkapan di padang lamun, status penangkapan ditentukan berdasarkan skala status menyerupai skala FAO dan dianalisis melalui pengukuran tangkapan per unit upaya (CPUE), tangkapan total dalam satu tahun (Y), mortalitas alami dalam bentuk mortalitas berbasis bobot (Mw), estimasi biomassa pada tahun yang sama (B), dan hasil tangkapan maksimum lestari (MSY). Analisis RAPSECS (rapid appraisal technique for evaluating seagrass ecosystems sustainability) menggunakan multidimensional scaling (MDS) diaplikasikan untuk menganalisis status keberlanjutan ekosistem lamun untuk setiap dimensi (ekologi, ekonomi, sosial, teknologi, institusi). Gabungan metode perbandingan berpasangan dengan geomean digunakan untuk menentukan status keberlanjutan umum dari ekosistem lamun. Analisis leverage digunakan untuk menemukan atribut yang paling berpengaruh terhadap status keberlanjutan setiap dimensi. Hasil penelitian menunjukkan bahwa secara umum struktur komunitas dan pola distribusi ikan pada kedua padang lamun TH dan EA ditemukan berbeda. Penangkapan ikan di padang lamun (baik BL ataupun KP) bukan merupakan pekerjaan utama dan hanya nelayan tertentu yang melakukan penangkapan. CPUE total maupun laju eksploitasi ikan lamun antara BL dan KP adalah relatif sama, dan status penangkapan mereka masih dalam kategori underexploitation. Secara umum, prioritas strategi pengelolaan ekosistem lamun di BL meliputi penguatan kelembagaan, pengembangan sumberdaya manusia, dan perbaikan lingkungan, sementara di KP meliputi penguatan kelembagaan dan pengembangan sumberdaya manusia.