Species composition and biology reproductions aspects of stingray (Batoidea) in south coast of Prigi waters, Trenggalek, East Java, Indonesia

Stingray (Batoidea) are often caught as bycatch in south coast of Prigi waters. The stingray resource has very limited in number and require a long time to reproduce. Attention must be paid to avoid the extinct of stingray resource. This research aimed to justify species composition and identify length weight relationship, sex ratio, and clasper maturity level of stingray (Batoidea) caught in south coast of Prigi waters. The research was carried out from December 2019 to April 2020 at Prigi archipelago fishing port as landing place. This study used a quantitative descriptive method with the number of samples that were successfully obtained as many as 97 stingray. During the study, 6 species of stingray (Batoidea) were identified, namely Taiwan guitarfish (Rhinobatos schlegelii), blotched fantail stingray (Taeniurops meyeni), Japanese devilray (Mobula japanica), bluespotted maskray (Neotrygon kuhlii), shark ray (Rhina ancylostoma), dan bluespotted fantail ray (Taeniura lymma). Result indicated that Taiwan guitarfish (R. schlegelii) and bluespotted maskray (N. kuhlii) were two dominant stingray species in south coast of Prigi waters with proportion of 47.42% and 41.24% respectively. Disk width (Dw) and weight (W) of Taiwan guitarfish (R. schlegelii) ranged from 15.2 cm to 24.6 cm and from 268 gr to 1060 gr respectively and bluespotted maskray (N. kuhlii) ranged from 17.3 cm to 39.3 cm and from 140 gr to 2006 gr respectively. Another analysis showed that Taiwan guitarfish (R. schlegelii) and bluespotted maskray (N. kuhlii) had length weight relationship equations W = 0.0202 Dw34699 and W=0.0351*Dw29848 respectively. The sex ratio of Taiwan guitarfish Taiwan guitarfish (R. schlegelii) dan bluespotted maskray (N. kuhlii) was 1:1.4 and 1:1.2 respectively. In addition, clasper maturity level of the Taiwan guitarfish (R. schlegelii) and bluespotted maskray (N. kuhlii) species was dominated by Non-Calcification (NC). In conclusion, The stingray (Batoidea) caught in south coast of Prigi waters were dominated by Taiwan guitarfish (R. schlegelii) and bluespotted maskray (N. kuhlii). Length weight relationship of Taiwan guitarfish (R. schlegelii) and bluespotted maskray (N. kuhlii) was allometric positive and isometric respectively. Both of them was in balance condition sex ratio and was dominated by immature stage. Hence fishing activities in south coast of Prigi waters should avoid the stingray as bycatch in order to preserve the stock.

Fishery and geospatial mapping of pelagic elasmobranchs from mechanised gillnetters of Tharuvaikulam, Thoothukudi, south-east coast of India

The pelagic elasmobranchs fishery of multiday gillnetters (MGNs) of Tharuvaikulam, Thoothukudi was studied during 2015-2016. Fishery data revealed that MGNs targeting scombrids and other large pelagic fishes also contribute to the pelagic elasmobranch landings accounting for 7.67 and 5.3% of total elasmobranchs landed at Tharuvaikulam during 2015 and 2016 respectively. The catch per unit effort (CPUE) varied from 2.09 to 175 kg (2015) and 13 to 124.95 kg (2016). In total, 15 species of pelagic elasmobranchs were recorded during the study period, which includes 7 species of sharks and 8 species of rays. The pelagic elasmobranchs fishery of Tharuvaikulam depends mainly on two species namely bigeye thresher, Alopias superciliosus and spinetail devilray, Mobula japanica. The geospatial mapping revealed that fishing grounds of MGNs was between 77° to 80°E longitudes and 7° to 9° N latitudes with depth ranging from 50 to 200 m. The persistence of fishing grounds of pelagic elasmobranchs was identified by classifying the fishing areas of Gulf of Mannar Biosphere Reserve (GOMBR) into seven zones. The results showed that more fishing happens in Zone 4, off Thoothukudi between 78° to 79°E and 8° to 9°N followed by Zone 7, off Kanyakumari between 77° to 78°E and 7° to 8°N. Seasonal analysis revealed that along with the targeted groups, the CPUE of pelagic elasmobranchs was higher during the pre-monsoon season. The present paper illustrates the zonal distribution of pelagic elasmobranchs in the fishing grounds of MGNs in GOMBR, along the south-east coast of India and the results of the study would serve as baseline information for formulating future management plans.

Assessing Indonesian manta and devil ray populations through historical landings and fishing community interviews

International concern is growing with regard to the sustainability of manta and devil ray (collectively mobulids) fisheries as demand for mobulid products has increased in international markets over the last decade. While Indonesia has been reported to be one of the worlds’ top three catchers of mobulid rays, detailed information on these fisheries and the status of Indonesian mobulid populations are lacking. Through collection of historical and recent mobuild fisheries data from published and unpublished sources, this study aimed to identify trends in abundance of Indonesian manta and devil rays and explore socio-economic factors and incentives associated with mobulid fisheries. Comparison of catches from 2001-5 to the most recent data from 2013-14 revealed dramatic declines in mobulid landings over the study period of 64% at Cilacap, 75% at Lamakera, and 94% at Tanjung Luar. The largest declines were observed for Manta spp. and the two large devil rays, Mobula tarapacana and Mobula japanica. Anecdotal reports indicated that catches had declined substantially at three additional sites and local extirpations are strongly suspected to have occurred at three locations. A lack of data on the population ecology of Indonesia’s mobulids makes it difficult to determine whether natural fluctuations may be playing a part in the declining catch rates. However, mobulid life history traits, including low reproductive rates and late age of sexual maturation, indicate that fishing pressure is likely the primary driver in these declines. Interviews in Lamakera, a community which depends on income from its targeted mobulid fishery, suggest that programs focused on education, training and infrastructure development to enable shifts to sustainable livelihood alternatives are likely to offer the most successful path to long-term conservation and management of manta and devil rays, while simultaneously yielding economic and social benefits to fishing communities.

Mobulid rays feed on euphausiids in the Bohol Sea

Mobulid rays have a conservative life history and are caught in direct fisheries and as by-catch. Their subsequent vulnerability to overexploitation has recently been recognized, but fisheries management can be ineffective if it ignores habitat and prey preferences and other trophic interactions of the target species. Here, we assessed the feeding ecology of four mobulids ( Manta birostris , Mobula tarapacana , M. japanica , M. thurstoni ) in the Bohol Sea, Philippines, using stomach contents analysis of fisheries specimens landed between November and May in 2013–2015. We show that the mobulids feed heavily on euphausiid krill while they are in the area for approximately six months of the year. We found almost no trophic separation among the mobulid species, with Euphausia diomedeae as the major prey item for all species, recorded in 81 of 89 total stomachs (91%). Mobula japanica and M. thurstoni almost exclusively had this krill in their stomach, while M. tarapacana had a squid and fish, and Ma. birostris had myctophid fishes and copepods in their stomachs in addition to E. diomedeae . This krill was larger than prey for other planktivorous elasmobranchs elsewhere and contributed a mean of 61 364 kcal per stomach (±105 032 kcal s.e., range = 0–631 167 kcal). Our results show that vertically migrating mesopelagic species can be an important food resource for large filter feeders living in tropical seas with oligotrophic surface waters. Given the conservative life history of mobulid rays, the identification of common foraging grounds that overlap with fishing activity could be used to inform future fishing effort.

PERIKANANDANASPEKBIOLOGI IKANPARI LAMPENGAN, Mobula japanica DI PERAIRANSELATAN JAWA

Ikan pari merupakan salah satu jenis ikan yang banyak didaratkan berasal dari Selatan Jawa. Salah satu jenis ikanpari yang belum banyak dilakukan penelitian adalah ikan pari lampengan (Mobula japanica). Tujuan penelitian ini adalah untuk mengetahui tentang perikanan dan aspek biologi jenis ikan tersebut di perairan Selatan Jawa sebagai informasi dasar bagi penentuan kebijakan pengelolaan perikanan Elasmobranchii. Penelitian menggunakan metode survei yang berlangsung dari Januari hingga Desember 2010 di Pelabuhan Perikanan Samudera Cilacap-Jawa Tengah. Sejumlah 165 ikan pari yang tertangkap oleh jaring insang diamati tingkat kematangan seksual, tingkat kematangan gonad, jenis kelamin dan ukuran lebar cawannya.Wawancara dilakukan terhadap para nelayan dan nahkoda kapal yang menangkap ikan pari lampengen tersebut secara langsung dan atau oleh enumerator. Hasil penelitian menunjukkan bahwa tangkapan per satuan usaha (CPUE) ikan pari lampengan bervariasi, yakni tertinggi pada bulan Juli (22,6 kg/ hari) dan terendah pada bulan Oktober (6,6 kg/hari). Frekuensi lebar tubuh ikan pari lempengen terendah terdapat pada ukuran antara 100-140 cmdenganmodus 120 cmyang termasuk kelompokmuda, sedangkan ukuran antara 150- 200 cm dengan modus 170 cm, termasuk kelompok dewasa. Frekuensi lebar tubuh tertinggi terdapat pada ukuran antara 200-260 cmdenganmodus 230 cm. Ikan pari lempengen sedikitnya terdiri atas 3 kelompok umur dengan modus sebaran lebar tubuh masing-masing 120, 170, dan 230 cm. Hubungan lebar tubuh (y) dan panjang klasper (x)mengikuti persamaan y=0,3784e0,0131x (r2=0,85), semakin bertambah lebar tubuh semakin bertambah panjang klaspernya.Perbandingan kelamin jantan dan betina adalah tidak seimbang (1,5:1). Sebagian besar kelompok umur ikan pari lampengan yang tertangkap tergolong usia muda, yang belummencapai pertumbuhan optimum(growth over fishing). Stingray is one of the species of fish that many landed came from the South of Java. One of the species that have not many research is JapaneseDevilray (Mobula japanica). The purpose of this study was to determine fisheries and biological aspects of Japanese Devilray, Mobula japanica in Indian Ocean as basic information for managing the elasmobranches fisheries. This study was conducted from January to December 2010 in the Ocean Fishing Port of Cilacap, Central Java. A total number of 165 individu of M. japanica caught by seine net and tuna longline were observed during the sampling periods. Body wide, sex, and gonadmaturation of those fishes were analyzed. Interviewswere also done to the fisherman and fishing master. The results showed that the body width of stingrays, M. japanica had the lowest frequency between 100-140 cm with mode of 120 cm,and grouped as young fish.Other groups has body width between 150-200 cm with mode 170 cm, and grouped as adult fishes. While the frequency of the highest body width was between 200-260 cm and 230 cmmode. At least, there were 3 cohorts ofM. japanica found in this study with the body width mode of 120, 170 and 230 cm. Exponential relationship between body width (y) and claspers’ length (x) was observed forM. japanica, that expressed by equation: y=0.3784e 0.0131x (r2=0.85), that mean the more width fish body, the more increase claspers’ length. Unbalance sex ratio of 1.5:1 was observed for this fish. CPUE for M. japanica were varied between 6,6 kg/day during October and 22,6 kg/day 0n July. Most of fish caught were young fishes under their maturity stages that indicated a tendency of growth over fishing.

Assessing Indonesian manta and devil ray populations through historical landings and fishing community interviews

International concern is growing with regard to the sustainability of manta and devil ray (collectively mobulids) fisheries as demand for mobulid products has increased in international markets over the last decade. While Indonesia has been reported to be one of the worlds’ top three catchers of mobulid rays, detailed information on these fisheries and the status of Indonesian mobulid populations are lacking. Through collection of historical and recent mobuild fisheries data from published and unpublished sources, this study aimed to identify trends in abundance of Indonesian manta and devil rays and explore socio-economic factors and incentives associated with mobulid fisheries. Comparison of catches from 2001-5 to the most recent data from 2013-14 revealed dramatic declines in mobulid landings over the study period of 64% at Cilacap, 75% at Lamakera, and 94% at Tanjung Luar. The largest declines were observed for Manta spp. and the two large devil rays, Mobula tarapacana and Mobula japanica. Anecdotal reports indicated that catches had declined substantially at three additional sites and local extirpations are strongly suspected to have occurred at three locations. A lack of data on the population ecology of Indonesia’s mobulids makes it difficult to determine whether natural fluctuations may be playing a part in the declining catch rates. However, mobulid life history traits, including low reproductive rates and late age of sexual maturation, indicate that fishing pressure is likely the primary driver in these declines. Interviews in Lamakera, a community which depends on income from its targeted mobulid fishery, suggest that programs focused on education, training and infrastructure development to enable shifts to sustainable livelihood alternatives are likely to offer the most successful path to long-term conservation and management of manta and devil rays, while simultaneously yielding economic and social benefits to fishing communities.