Fisheries and Aquatic Sciences

Keanekaragaman jenis ikan karang merupakan suatu indikator penting yang dapat menggambarkan perubahan lingkungan perairan karang. Perubahan habitat karang adalah resiko yang mungkin dihadapi sebagai akibat pembangunan. Penelitian dilakukan di perairan pantai Pangandaran dengan tujuan mengkaji kesehatan terumbu karang dan indeks ekologis komunitas ikan karang. Metode yang digunakan dalam penelitian ini adalah line intercept transect untuk menentukan persen tutupan karang dan metode sensus visual untuk menentukan keanekaragaman ikan karang pada area seluas 250m2. Hasil penelitian menunjukkan kesehatan terumbu karang pada kondisi buruk, tutupan karang hidup 11,4 -20,74%. Teridentifikasi 66 jenis ikan karang dengan kriteria kepadatan sangat jarang (0,59 – 0,91) ind/m2. Indeks kekayaan ikan karang pada kategori baik (4,60-8,68), keanekaragaman jenis ikan karang termasuk dalam kategori sedang (2,57-3,36). Tidak terjadi dominasi jenis ikan karang tertentu (0,05-0,120) dan kemerataan populasi di lokasi penelitian termasuk tinggi (0,81-0,87). Reef fish diversity is a major indicator to expose a current environmental state of coral reefs. Economic developments probably lead to habitat alteration risks. The research was conducted in Pangandaran Beach Waters, Batu Karas, Pananjung Barat, Pananjung Timur. The research objective was, to assess the reef health, and to fine out several diversity indices of reef fish communities. Methods used for those are a line intercept transect and census visual technique within area of 250 m2. The results showed that all of the area had a poor reef health category(11,4-20,74%), reef fish densities were grouped in very rare areas, especially < 1-5 ind/m2. Richnes indices had a good category(4,60-8,68), shannon diversity indices of reef fish felt in the fair category(2,57-3,36), dominance indices of reef fish felt in the low category(0,05-0,120) and evenness indices were felt in a high category(0,81-0,87).

This research examines the function changes around the coral reef ecosystem caused by coral disease in Paraja Bay. The research aims to identify coral disease and the correlation between diseases and reef coral species. These identifications of coral diseases can be used to assess corals’ growth process, reproduction, and structural changes. The in-situ data was collected in February 2022 at 16 stations on each side of four small islands. The closeness relationship analysis was performed using PCA and XLstat. The results show that the disease prevalences in four small islands are varied, namely Badul Island (17.2%), Mangir Island (6.96%), Oar Island (2.66%), and Umang Island (4.86%) with an average of 7.91%. The coral diseases found in all stations were Trematodiasis and White Syndrome. Corals with Trematodiasis symptoms were Favia sp., Favites sp., and Platygyra sp., while ones with White Syndrome were Acropora sp., Favites sp., and Pavona sp. The existence of the diseases indicates the need for ecosystem restoration to include environmental aspects and community activities. This restoration action can accelerate the process of habitat and associated biota recovery.

The intensive fishing and lack of data for squid fisheries in Belitung waters have increased the risk of stock population decline, which could lead to large economic losses. Comprehensive studies on the biological aspects and stock status of squid were crucial to developing some management recommendations. This study investigated several population ecological characteristics (size distribution, length-weight relationship, condition factors, maturity stages, length at maturity, and growth parameters), the stock status, and the biological reference points of mitre squid (Uroteuthis chinensis Gray, 1849) in Belitung waters. The squid’s biological data were collected from August 2023 to March 2024. The stock status was investigated by several approaches, including length-converted catch-curve (LCC), yield per recruit (YPR) analysis, and length-based spawning potential ratio (LB-SPR). This study revealed that the mean size of male and female squid captured by squid jig was 16.22 ± 6.72 cm and 14.23 ± 3.65 cm (Mean of mantle length ± standard deviation), with the length at first maturity (Lm50) of 19 cm for males and 12 cm for females. Female gonadally mature squid were found throughout the year, with the largest proportion in January (93%). The overfishing condition of U. chinensis has occurred based on the current exploitation level for male (Ecur: 0.63; Fcur: 2.61 year-1) and female (Ecur: 0.72; Fcur: 4.39 year-1) that exceeds both the optimal exploitation rate (Eopt=0.5) and the fishing mortality given the maximum yield per recruit (Male Fmax: 2.08 year-1; Female Fmax: 3.35 year-1). Recruitment overfishing has also occurred based on the current spawning potential ratio of 18%. Reducing the fishing trips by 24%, applying a season closure in January, and enlarging the selectivity to 15 cm were recommended to raise the squid stock and ensure the sustainability of squid fisheries in Belitung waters.