Intensity and Predilection of Helminth Parasites of the Red Snapper (Lutjanus argentimaculatus)

Marine fish, particularly the red snappers, are often exposed to helminth parasitic infestation. As a result of the parasitic infestation, the fish population, the fish weight, and the morphological changes in the fish are shrinking. The present research aimed to find out the intensity and predilection of the helminth ectoparasites over the infection of the red snapper (Lutjanus argentimaculatus) and employed the survey method for this purpose. The sampling was carried out by the purposive sampling technique. The sample obtained consisted of 30 fish, 20% of the total red snapper population of 150 fish reared in the floating net cages of Balai Besar Perikanan Budidaya Laut Lampung. The intensity of the fish infestation by a mixture of Haliotrema epinepheli and Benedenia epinepheli was 132.5 individuals/fish. Neobenedenia girellae and Haliotrema epinepheli infected fish with an intensity of 149.41 individuals/fish. The 66.7% of Benedenia epinepheli had a predilection for the dorsal fin, and 33.3% for the anal fin. In Neobenedenia girellae, 57.1% had a predilection for the body surface, 37.2% for the head surface, and 5.7% for the dorsal fin. In conclusion, all sampled fish were positively infected with helminth ectoparasites, including Neobenedenia girellae, Haliotrema epinepheli, and Benedenia epinepheli.

INDEKS PERTUMBUHAN IKAN KAKAP MERAH DAN KERAPU LUMPUR PADA PERIKANAN BUBU DASAR DI PERAIRAN BUNYU

Pulau Bunyu di Propinsi Kalimantan Utara memiliki sumberdaya hayati ekosistem perairan laut yang berlimpah dan bernilai ekonomis yang tinggi, dimana masyarakat pulau Bunyu memanfaatkan potensi ekosistem perairan laut digunakan sebagai potensi perikanan dalam hal penangkapan dengan menggunakan alat tangkap bubu dasar (bottom fish pot). Hasil tangkapan yang bernilai ekonomis berupa ikan kakap merah dan ikan kerapu yang terdapat di perairan ekosistem laut pulau Bunyu. Tujuan penelitian adalah menganalisis pertumbuhan dan struktur ukuran ikan kakap merah (Lutjanus argentimaculatus) serta ikan kerapu lumpur (Epinephalus malabaricus) yang berasal dari perairan pulau Bunyu. Data yang diteliti berupa parameter pertumbuhan yaitu panjang total dan panjang standar, berat total, jenis kelamin, tingkat kematangan gonad, dan berat gonad. Hasil penelitian ikan kakap paling banyak tertangkap ukuran panjang 40,49-47,61 cm dan bobot 990,05-1.451,68 gram. Pada ikan kerapu lumpur dengan ukuran panjang 43,73-50,13 cm dan berat 800,94-1.308,70 gram. Sifat pertumbuhan pada ikan kakap merah adalah allometrik negatif. Nilai indeks kondisi berbentuk kurus pada sampel ikan kakap merah. Sifat pertumbuhan pada sampel ikan kerapu pada variabel panjang total dengan berat total bersifat allometrik positif dan pada variabel panjang standar dan panjang cagak dengan berat total bersifat allometrik negatif.

Growth Performance of the Mangrove Red Snapper (Lutjanus argentimaculatus) in Freshwater Pond Comparing Two Stocking Densities and Three Feed Types

The mangrove red snapper Lutjanus argentimaculatus (Forsskål 1775) is a high value, euryhaline marine fish with potential as a species for freshwater aquaculture. This study evaluated the growth and cost efficiency of the species in a freshwater pond in two experiments with three replications: (a) comparing stocking densities: (1) 0.5; (2) 1; and (3) 3 fish fish•m-2 reared for six months fed three times a day with trash fish to apparent satiation; and (b) comparing feed types: (1) trash fish; (2) moist diet; and (3) formulated dry pellet at a stocking density of 1 fish•m-2 fed to apparent satiation three times a day for seven months. The stocking density (SD) experiment showed significantly higher weight gain, absolute growth and specific growth rate (P<0.05) in 0.5 fish•m-2 SD (184.9 g; 1.04 g•day-1; 2.50%/day) than 3 fish•m-2 SD (172.7 g; 0.96 g•day-1; 2.38 %•day-1). No significant difference was detected between 0.5 fish•m-2 SD and 1 fish•m-2 nor between 1 fish•m-2 and 3 fish•m-2 (P>0.05). Survival rate (SR) and feed conversion ratio (FCR) were not statistically different between treatments (P>0.05), which ranged from 78% to 92% and 5.0 to 5.9, respectively. Cost analysis showed high net returns for 1 and 3 fish•m-2 SD but low in 0.5 fish•m-2 SD. The feeding experiment study showed that feed types significantly affected weight gain, SGR, and SR (P<0.05). Snappers fed with trash fish attained significantly higher mean absolute growth (298.2 g) and SGR (1.81%/day) than those fed moist feeds (232.8 g and 1.61%/day, respectively) and formulated feeds (236.1 g and 1.51%/day, respectively). The survival rate was significantly higher in snappers fed trash fish (93.33%) and dry pellets (94.00%) than fed moist feeds (81.34%). FCR in trash fish, moist and dry pellet treatment was 6.4, 6.3, and 2.7, respectively. Cost analysis showed high net returns for trash fish and formulated pellet fed snappers but low in moist diet feed treatment. Cost-benefit analysis showed the feasibility of mangrove red snapper for freshwater aquaculture at a recommended stocking density of 1 to 3 fish•m-2 using trash fish, moist diet, or formulated dry pellet.

Analisis Morfometrik dan Klasifikasi Bentuk Lutjanus spp. Berdasarkan Gambar Digital

Lutjanus spp is a genus of the Lutjanidae family. The number of Lutjanus spp in waters around the world are 72 species. For this amount, 33 of them living on Indonesian waters. According to the IUCN List (2020), about ten species have decreased in population. One of the causes that population decline in several species is, the recording of capture fisheries has very limited production data. This is caused by the difficulty of identification in the field, which results in the overfishing of certain species. The identification process can be carried out based on morphometric features. Geometric morphometrics can be explaining morphological variations objectively and accurately. There are several methods used to represent the shape of an image in general. Namely point linking, complex coordinate, tangent angle, contour curvature, and triangle-area representation.Lutjanus spp by calculating the value of landmark positions, landmark curvature, changes in landmark angle, landmark distance, and landmark inclination. The results of feature extraction were used to classify Lutjanus spp (Lutjanus argentimaculatus, Lutjanus bohar, Lutjanus carponotatus, Lutjanus fulviflamma, and Lutjanus sebae). The results of this study indicate that the morphometric geometric approach can extract the feature values of the position of landmarks, a curvature of landmarks, changes in the angle of the landmark, distance of landmark, and the inclination of the landmark. The classification results using the Support Vector Machine (SVM) classification technique can distinguish Lutjanus spp with an accuracy rate of 65.03%. Thus, the application of SVM can be used to classify Lutjanus spp species, which will be useful in the identification process. Keywords: clasificasion, identification, morphometric geometric, Lutjanus spp, support vector machine. AbstrakLutjanus spp. adalah salah satu marga dari famili Lutjanidae. Jumlah spesies Lutjanus spp di perairan seluruh dunia yaitu 72 spesies. Dari 72 spesies tersebut 33 diantaranya hidup di perairan Indonesia. Menurut IUCN (2020) sekitar 10 spesies mengalami penurunan populasi. Salah satu penyebab menurunnya populasi pada beberapa spesies yaitu pencatatan data produksi perikanan tangkap masih sangat terbatas. Hal ini disebakan oleh sulitnya identifikasi di lapangan sehingga mengakibatkan overfishing pada spesies tertentu. Proses identifikasi dapat dilakukan berdasarkan ciri morphometrik. Geometri Morfometrik dapat menjelaskan variasi morfologi secara objektif dan akurat. Ada beberapa metode yang digunakan dalam merepresentasi bentuk suatu citra secara umum. yaitu point linking, complex coordinate, tangent angle, contour curvature, serta triangle-area representation. Pendekatan morphometric geometric pada penellitian ini digunakan untuk mengekstraksi fitur bentuk Lutjanus spp. dengan menghitung nilai posisi landmark, kelengkungan landmark, perubahan sudut landmark, jarak landmark, dan kemiringan landmark. Hasil ekstraksi fitur digunakan untuk mengklasifikasikan spesies Lutjanus spp. (Lutjanus argentimaculatus, Lutjanus bohar, Lutjanus carponotatus, Lutjanus fulviflamma, dan Lutjanus sebae). Hasil penelitian ini menunjukkan, bahwa pendekatan Geometri Morfometrik dapat melakukan ekstraksi nilai fitur posisi landmark, kelengkungan landmark, perubahan sudut landmark, jarak landmark, dan kemiringan landmark. Adapun hasil klasifikasi menggunakan teknik klasifikasi Support Vector Machine (SVM) mampu membedakan spesies Lutjanus spp. dengan tingkat akurasi sebesar 65.03%. Dengan demikian, penerapan SVM dapat digunakan untuk melakukan klasifikasi terhadap spesies Lutjanus spp yang akan bermanfaat pada proses identifikasi.Kata kuncis: klasifikasi, identifikasi, geometri morfometrik, spesies lutjanus spp., support vector machine.

Population structure undetectable using genetic markers in Mangrove Jack Lutjanus argentimaculatus from its cool-water range limit in eastern Australia

Failure to consider genetic structure in fish populations when collecting aquaculture broodstock can negatively affect fitness, and hence conservation and management goals. Here we used mitochondrial DNA from the 5’ end of the control region (D-loop) and four microsatellite markers to evaluate population genetic structure in the Mangrove Jack Lutjanus argentimaculatus with a view to guiding broodstock collection at the southern extremity of its east Australian range. There was no evidence of genetic structure within the entire tropical, subtropical and temperate east Australian distribution of L. argentimaculatus. Although this species may exhibit clinal morphological and life-history variation at its southern range limit, we did not detect wide- or fine-scale spatial genetic structure to indicate the presence of non-random evolutionary processes. Broodstock collection of L. argentimaculatus need not be geographically restricted in eastern Australia, but fisheries management should consider variation in life history and recruitment success at the species’ edge.

Distribution of Mangrove Red Snapper Lutjanus argentimaculatus in response to hydrodynamic condition at the reef patches of Lankayan, Sugud Islands Marine Conservation Area, Sabah, Malaysia

The species Lutjanus argentimaculatus is a prized food-fish in the tropical and subtropical fisheries, as well as the aquaculture industry. This study investigated the distribution of L. argentimaculatus at three patch reefs of Lankayan Island, within the Sugud Islands Marine Conservation Area. Fish surveys of this species were conducted 12 times at each of the selected patch reefs, from August 2016 until March 2017. In addition to taking underwater video footages, hydrodynamic parameters, i.e. water current direction and current speed were recorded during each survey. The distribution patterns of the fish were then plotted against these parameters to determine any correlation, in response to these parameters. As a result, we found a significant relationship between the current direction and the position of L. argentimaculatus at the reef where the schoolings were found to occur. We found that regardless of the current speed, the schools of L. argentimaculatus were always present at the reef slope facing the incoming current. This finding is important for the management and conservation of this species, which is a targeted species in the Live Reef Fish Food Trade (LRFFT), and is useful for the manager of a Marine Protected Area (MPA) in general. This finding is also important as it provides useful insights into the ecology of Lutjanus spp.