Status Pemanfaatan dan Dampak Penangkapan terhadap Sumberdaya Rajungan (Portunus pelagicus) di Perairan Lamongan, Jawa Timur.

Abstract

Hasil tangkapan rajungan (blue swimming crab) dimanfaatkan dan berkontribusi cukup besar pada sektor perikanan dan kelautan terutama sebagai komoditi ekspor ke negara tujuan seperti USA mencapai 73% dan beberapa negara lainnya. Sentra perikanan rajungan di WPPNRI 712 khususnya Lamongan memiliki rata-rata nilai produksi sebesar 46 miliar rupiah per tahun. Saat permintaan ekspor tinggi dan harga jual rajungan tinggi, memicu nelayan untuk meningkatkan intensitas penangkapan rajungan. Stok sumberdaya rajungan di alam cenderung makin berkurang, banyak tertangkapnya bycatch, bahkan telah terjadinya overfishing di beberapa lokasi. Besarnya tangkapan non target (bycatch) dapat berdampak serius bagi sumberdaya perikanan, baik secara langsung maupun tidak langsung terhadap ekosistem. Oleh karena itu perlu adanya pengelolaan yang baik agar stok sumberdaya rajungan di alam tetap terjaga. Dalam rangka implementasi Rencana Pengelolaan Perikanan (RPP) Rajungan Indonesia serta strategi pemanfaatan (harvest strategy) perikanan rajungan khususnya di WPP 712, maka dilakukan monitoring secara berkala. Parameter Length Based Spawning Potential Ratio (LB-SPR) merupakan indikator utama yang digunakan untuk mengevaluasi status stok rajungan. Sementara itu dampak penangkapan terhadap non target dimonitor berdasarkan struktur bycatch. Hal tersebut merupakan landasan pentingnya penelitian ini. Penelitian ini bertujuan mendeskripsikan unit penangkapan rajungan, mengevaluasi status pemanfaatan sumberdaya rajungan dan dampak ekologis kegiatan penangkapan rajungan terhadap target (rajungan) dan non target di Perairan Lamongan, Jawa Timur. Penelitian ini dilakukan dengan metode observasi, survei, dan studi literatur untuk mendapatkan data dan informasi terkini sesuai dengan tujuan penelitian. Metode survei dengan melakukan wawancara terhadap 60 responden yang diperoleh melalui purposive sampling method untuk mengetahui informasi unit penangkapan rajungan. Sebanyak 3600 individu sampel rajungan dari alat tangkap bubu, arad, dan trammel net diperoleh melalui metode cluster sampling. Sementara itu bycatch dari ketiga alat tangkap tersebut dikumpulkan melalui simpel random sampling. Pengolahan data menggunakan perangkat lunak microsoft excel dan R-Studio packages LB-SPR dan TropFishR. Analisis data ditujukan untuk mendeskripsikan unit perikanan rajungan, status pemanfaatan rajungan, dan dampak ekologis terhadap target dan non-target di Perairan Lamongan, JawaTimur. Hasil penelitian menunjukkan terdapat 456 unit arad, 25.625 unit bubu, 364 unit trammel net, 3598 nelayan, dan 1424 unit perahu di lokasi studi. Sebaran ukuran sampel rajungan betina 52 – 157 mm, sedangkan jantan 57 – 161 mm. sifat pertumbuhan rajungan jantan dan betina yaitu allometrik positif. Parameter biologi rajungan betina memiliki nilai L∞ = 156,95 mm, K = 1,34 per tahun, M = 1,4 per tahun, dan E = 0,69, sedangkan pada rajungan jantan L∞ = 167,58 mm, K = 1,17 per tahun, M = 1,4 per tahun, dan E = 0,72. Nilai parameter SPR rajungan sebesar 23% atau menunjukkan bahwa status stok sumberdaya rajungan di iv Perairan Lamongan memiliki status fully moderately. Komposisi hasil tangkapan rajungan pada bubu, trammel net, dan arad berturut-turut 90%, 35%, dan 19% serta hasil tangkapan sampingan menggunakan bubu 10%, trammel net 65% , dan arad 81%. Komposisi bycatch berdasarkan jenis hasil tangkapan bubu didominasi oleh keong macan (Babylonia spirata) sebanyak 61 individu, arad oleh teri gelagar (Stolephorus indicus) 1866 individu, dan trammel net oleh mata belo (Hilsa kelee) 327 individu. Indeks keragaman Shannon – Wiener (H‟) untuk bubu, arad, dan trammel net berturut-turut 3,09; 3,63; dan 5,04. Penelitian ini merekomendasikan: 1) pemerintah perlu menerapkan atau mengimplementasikan PERMEN KP No. 18 Tahun 2021 kepada nelayan untuk tidak menggunakan alat tangkap arad dalam perikanan rajungan sesuai regulasi yang berlaku; 2) perlu adanya program aksi pemulihan stok (rebuilding stock) rajungan di alam; 3) perlu dilakukan monitoring secara berkala sepanjang tahun agar memperoleh data untuk parameter LB-SPR yang lebih baik di Perairan Lamongan; 4) perlu melanjutkan penelitian ini waktu dan musim yang berbeda untuk mengetahui dinamika rajungan di lokasi studi.

The catch of crabs (blue swimming crab/BSC) is utilized and contributes greatly to the fisheries and marine sector, especially as an export commodity to destination countries such as the USA reaching 73% and several other countries. The crab fishery center in WPPNRI 712, especially Lamongan, has an average production value IDR 46 billion per year. When export demand is high and the selling price of crab is high, it promotes fishers to increase the intensity of crabs fishing. The stock of crabs in fishing ground is tend to decrease, many bycatches are caught, and there has even been overfishing in some locations. The amount of non-target catch (bycatch) can have a serious impact on fishery resources, either directly or indirectly on the ecosystem. Therefore, it is necessary to have good management so that the stock of natural resources is maintained. In term of implementing the crab fishery management plan (RPP) and its fishery harvest strategy, particularly in FMA 712, periodic monitoring should be done. The parameter of Length Based Spawning Potential Ratio (LB-SPR) is one of the main indicators used to evaluate the BSC stock status. Meanwhile, the impact of fishing on non-target species is monitored based on the structure of the bycatch. This is the basis for the importance of this research. This study aims to describe the crab fishing unit, to evaluate the status stock of the crab resource, and the ecological impact of crab fishing on target and non-target species in Lamongan Waters, East Java. This research was conducted using observation, survey, and literature studies methods to obtain the data and information to achieve the research objectives. The survey method was conducted by interviewing 60 respondents obtained through a purposive sampling method, particularly to get information on the crab fishing unit. The total of 3600 crab sampels resulted from traps, arad (mini trawl), and trammel net were collected by means of cluster sampling method.Meanwhile the bycatch species from the gears were collected by simpel sampling technique. The data were analyzed by microsoft excel software, R Studio LB-SPR and TropFishR packages. Data analyses were conducted to describe the crab fishing unit, the status stock of the crab resource, and the ecological impact on target and non-target catch species in Lamongan Waters, East Java. The results of the study showed that there were 456 units of arads, 25,625 units of traps, 364 units of trammel nets, 3598 fishers, and 1424 units of fishing boats at the study site. The distribution of sample size for female crabs were 52 – 157 mm, while the male crabs were 57 – 161 mm. The growth pattern of male and female crabs was allometric positive. The biological parameters of female crabs have a value of L∞ = 156.95 mm, K = 1.34 per year, M = 1.4 per year, and E = 0.69, while for the male crabs of L∞ = 167.57 mm, K = 1.17 per year, M = 1.4 per year, and E = 0.72. The crab SPR parameter value was 23% which indicates that the crab resource stock in Lamongan waters has a „fully-moderately‟ status. The composition of crab catches on traps, trammel nets, and arads were 90%, 35%, and 19%, respectively, and by-catch using traps was 10%, trammel nets 65%, and vi arads 81%. The composition of bycatch based on the type of trap caught was dominated by spiral babylon (Babylonia spirata) 61 individuals, arads by indian anchovy (Stolephorus indicus) 1866 individuals, and trammel net by kelee shad (Hilsa kelee) 327 individuals. The Shannon – Wiener Diversity Index (H') is high with H' traps, arads, and trammel nets is 3.09; 3.63; and 5.04 respectively. This research recommends:1) the government should implement the regulation 18 2021 particularly not using mini trawlas fishing gear in BSC fisheries following regulations; 2) implementation of rebuilding stock program for blue swimming crab; 3) it is necessary to conduct regular monitoring throughout the year to obtain better data for LB-SPR parameters in Lamongan Waters; 4) it is necessary to continue this study at different times and seasons in temporal basis of fishing season to consider the dynamics of the crab fishery in the study location