Ikan oskar (Amphilophus citrinellus) merupakan ikan asing di Waduk Ir. H. Djuanda yang saat ini merupakan ikan yang paling banyak tertangkap di waduk tersebut. Penelitian ini dilakukan pada Oktober 2011–Januari 2012 di Waduk Ir. H. Djuanda, Jawa Barat, dengan tujuan untuk mengetahui beberapa aspek yang berkaitan dengan pemijahan ikan oskar. Contoh ikan ditangkap menggunakan jaring insang. TKG diamati secara visual dan fekunditas dihitung menggunakan metode gravimetrik. Total ikan contoh yang tertangkap selama penelitian berjumlah 460 ekor yang berasal dari enam stasiun pengamatan. Hasil penelitian menunjukkan panjang total dan bobot tubuh ikan berkisar antara 62–210 mm dan 4,81–187,18 gram. Rasio kelamin ikan seimbang. Ukuran ikan jantan dan betina terkecil yang ditemukan matang gonad adalah 125 mm dan 121 mm. Ikan yang matang gonad paling banyak ditemukan pada bulan Desember untuk ikan betina dan Januari untuk ikan jantan. Fekunditas total berkisar antara 729–3.299 butir. Ikan oskar merupakan ikan pemijah bertahap.

Buyan and Tamblingan lakes were often mentioned as twin lake because of its adjacent location. These two lakes were separated by approximately one-kilometer forest. Studies which recorded the fish species in those lakes were very limited so that a study was needed regarding that conditions as the initial step of management. This study aims to reveal and analyze the ratio of native and alien fish species which were found in Buyan and Tamblingan lakes, Bali. The fish sampling was held three times in different months at Buyan and Tamblingan lakes during 2017-2018, using a purposive sampling method. There were six locations sampling fish on each lake. It used experimental gill net with mesh size 0.5; 1.0; 1.5; 2.0; 2.5; 3.0; 3.5; 4.0 inches and trap. Three of the nine species that found in Buyan and Tamblingan lakes were native fish species. The ratio of native and non-indigenous fish caught in Buyan lake was bigger than from Tamblingan lake. Based on the length size of the most captured fish, the native fish of Osteochilus vittatus in Buyan lake was longer than Tamblingan, while the non-indigenous one, Poecillia reticulata had the same length size on the two lakes.

Tuna sirip kuning (Thunnus albacares) merupakan hasil tangkapan terbanyak dibandingkan dengan jenis tuna lainnya di Indonesia. Ketersediaan stok tuna sirip kuning di Samudra Hindia, pada saat ini, diperkirakan dalam keadaan lebih tangkap. Oleh karena itu, pengelolaan secara tepat dan bertanggungjawab penting dilakukan untuk melindungi spesies tuna, salah satu caranya dengan mengkaji alat tangkap yang digunakan. Tulisan ini bertujuan untuk mengungkapkan produktivitas dan hasil tangkapan armada tonda, serta struktur ukuran dan hubungan panjang bobot ikan tuna sirip kuning yang di daratkan di selatan Jawa. Komposisi tangkapan tertinggi dari armada tonda diseluruh pendaratan ikan tuna di selatan Jawa terdiri atas tuna sirip kuning dan cakalang. Analisis CPUE menunjukkan hasil yang fluktuatif di setiap lokasi pendaratan tuna sirip kuning di Selatan Jawa. Tuna sirip kuning yang tertangkap di selatan Jawa dengan armada tonda sebagian besar adalah ikan yang belum layak tangkap karena berukuran kurang dari 100 cmFL. Struktur ukuran panjang tuna sirip kuning yang tertangkap semakin ke Timur semakin panjang ukurannya. Pola pertumbuhan tuna sirip kuning yang tertangkap di Binuangeun memiliki pola isometrik, PPN Palabuhanratu bersifat allometrik Positif, PPP Sadeng, P2SKP Pacitan, PPN Prigi dan P2SKP Sendang Biru bersifat allometrik negatif. Yellowfin tuna (Thunnus albacares) is the largest catch compared to other tuna species in Indonesia. The availability of yellowfin tuna stock in the Indian Ocean, at present, is estimated to be in overfished condition. Therefore, proper and responsible management is important to protect the species. One of the ways is by studying the used fishing gear. This paper aims at determining vessel’s productivity, as well as composition, size structure and length-weight relationship of yellowfin tuna catches from troll line fleet in the Indian Ocean part of south Java. The highest catch of tuna in all of the troll line landing places was yellowfin tuna, following by skipjack tuna. CPUE analysis showed fluctuating results at each landing site. Yellowfin tuna sizes caught by troll line fleet were mostly less than 100 cmFL and categorized as should not be properly caught. Geographically, getting to the east the average size of the catches tend to be larger. The growth pattern of yellowfin tuna catches landed in Binuangeun was isometric; Palabuhanratu was positive allometric; while those landed in Sadeng, Pacitan, Prigi and Sendang Biru were negative allometric.

ABSTRAKIkan tembang (Sardinella gibbosa Bleeker, 1849) adalah salah satu jenis ikan pelagis kecil, bernilai ekonomis penting serta banyak tertangkap di perairan Prigi dan sekitarnya. Informasi terkait ikan ini masih sangat terbatas di perairan Prigi. Penelitian ini bertujuan untuk mengungkap beberapa aspek biologi ikan tembang hasil tangkapan pukat cincin di perairan Prigi dan sekitarnya. Penelitian berlangsung selama lima bulan, dari Mei hingga September 2019. Ikan tembang yang dijadikan contoh merupakan hasil tangkapan pukat cincin yang didaratkan di PPN Prigi. Contoh ikan yang diukur panjang dan ditimbang bobotnya berjumlah 705 ekor. Tiga ratus diantaranya kemudian dibedah untuk diamati jenis kelamin dan tingkat kematangan gonadnya secara visual. Analisis data dilakukan menggunakan regresi power yang diuji menggunakan uji-t untuk hubungan panjang bobot, uji khi kuadrat untuk menentukan keseimbangan nisbah kelamin, dan fungsi logistik untuk menentukan ukuran pertama kali ikan matang gonad. Panjang cagak ikan yang dianalisis berkisar antara 91-183 mm dengan ikan terbanyak pada selang kelas 110-119 mm. Pola pertumbuhan ikan tembang adalah allometrik negatif dengan nisbah kelamin yang seimbang. Ukuran pertama kali matang gonad ikan tembang di perairan Prigi dan sekitarnya adalah 128 mm. Sebagian besar ikan tembang yang tertangkap pada alat tangkap pukat cincin adalah ikan tembang yang masih belum dewasa. Kata Kunci: Ikan tembang; kematangan gonad; reproduksi; pukat cincin; Prigi Jawa Timur ABSTRACTGoldstripe sardinella (Sardinella gibbosaBleeker, 1849) is a kind of small pelagic fish, economically important and caught a lot in Prigi and adjacent waters. The information regarding this fish was still very limited in Prigi waters. This study aimed to reveal several aspects of the biology of goldstripe sardinella caught by purse seine in Prigi and adjacent waters. The research was held for five months, from May to September 2019. Fish samples were from purse seiners that landed the caught at PPN Prigi. There were 705 fish measured and weighed. Three hundred of them were dissected to be observed the sex and gonadal maturity visually. Data analysis was performed using power regression which was tested using t-test for the relationship of weight length, chi-square test to determine the balance of sex ratio, and logistic function to determine the first length of maturity. The length of the fish was ranged from 91-183 mmFL and mostly was at 110-119 mmFL length class. The growth pattern of the goldstripe sardinella was allometric negative with a balanced sex ratio. The first length of maturity for goldstripe sardinella in Prigi and adjacent waters was 128 mm. Most of the fish which were caught by purse seine were still immature.

Gillnet is the most common fishing gear used by fishers in Ir. H. Djuanda Reservoir. Currently, gillnet catches are dominated by midas cichlid (<em>Amphilophus citrinellus</em>) which is not the main target catch. To some extent, their presence is even considered intrusive by the fishers. The aim of this study is to reveal the optimum gillnet mesh size in catching this alien species, which in turn can be useful to control the fish population in Ir. H. Djuanda Reservoir. The study was conducted from August 2011 to January 2012. The mesh size of the gillnets were 1, 1.5, 2, 2.5, 3, and 3.5 inches. The total midas cichlid caught were 628 fish which were mostly caught in 1.5 inches sized gillnet. Length first mature fish is 13.31 cm. The optimum size of fish caught in the mesh of 1.5, 2, 2.5, 3, and 3.5 inches are 9.7, 12.9, 16.2, 19.4, and 22.6 cm, respectively.

Highlight Research Morphoregression and reproduction aspect of bonylip barb was analyzed Fork length more accurately to estimate the body weight Lm50 of bonylip barb in Tamblingan Lake was 116 mmTL Growth pattern is isometric Good reproduction aspect   Abstract Bonylip barb (Osteochilus vitattus Valenciennes, 1842) is one of many native fish inhabiting Tamblingan Lake. The information about this species in Tamblingan Lake is rare which requires fulfilment in information gaps for the management of bonylip barb. The aims of this research were to find out the length-length relationship, length-weight relationship, length at first maturity, sex ratio, gonadal maturity stage, gonadosomatic index (GSI), fecundity, as well as spawning period and location in Tamblingan Lake. The fish sample was captured with experimental gillnet that was set in the afternoon and hauled in the next morning. Length and weight of every sample were taken. All samples were dissected to observe the sex and gonad. Fork length was the type of length with higher accuracy to estimate the body weight than the other length character. Growth pattern of this species was isometric. Lm50 of bonylip barb in Tamblingan Lake was 116 mmTL. Sex ratio of bonylip barb was imbalanced (1.00:0.82). Gonad maturity stage I-V was found during the research with GSI between 0.16-15.50 for male fish and 0.43-32.82 for female fish. The highest GSI was found in March, 15.50 for male fish and 32.73 for female fish. Mature fish were discovered in all stations in every month of sampling. The fecundity of bonylip barb ranged between 2,792-279,326 eggs. The length-length and the length-weight showed a strong relationship. The fish was isometric. Based on the growth pattern and the reproductive aspects, the population of bonylip barb in Tamblingan Lake was in good condition.

Ikan ekor pedang (Xiphophorus hellerii) merupakan jenis ikan asing yang mendiami catur danau Bali (Danau Tamblingan, Danau Buyan, Danau Bratan dan Danau Batur). Tujuan penelitian ini adalah untuk mengungkapkan nisbah kelamin, pola pertumbuhan dan kondisi ikan ekor pedang di catur danau Bali. Nisbah kelamin ikan ekor pedang di keempat danau berada dalam keadaan tidak seimbang. Proporsi ikan jantan di Danau Tamblingan, Danau Beratan dan Danau Batur lebih banyak daripada ikan betina dan kondisi sebaliknya ditemukan di Danau Buyan. Pola pertumbuhan ikan jantan di catur danau Bali adalah alometrik negatif dan ikan betina menunjukkan pola pertumbuhan alometrik negatif di Danau Tamblingan dan Danau Beratan dan pola pertumbuhan isometrik di Danau Buyan dan Danau Batur. Spesies ikan ini berada dalam kondisi baik di catur danau Bali dengan nilai faktor kondisi berkisar antara 0,47–1,54 dengan rerata 0,92 untuk ikan jantan dan 0,43–2,94 dengan rerata 1,12 untuk ikan betina.

Rasbora sp. is one of native fish species that inhabit in Tamblingan Lake. Several publication that discussed about this species in other ecosystem was published, but very rare information in Tamblingan Lake. The aims of this research ware determine the length-length relationships, growth pattern and condition Rasbora sp. in Tamblingan Lake. Fish sampling conducted from January to December 2019 in Tamblingan Lake. The sampling method was purposive sampling which did alternately every month on five sampling station that representing the condition of Tamblingan Lake. The result shown, all character of length has strong correlation with body weight of fish, but the total length (TL) was the most accurate measure to estimating the body weight of Rasbora sp.  The growth pattern of Rasbora sp. was isometric and the condition of this fish in good condition.