Reproductive biology and range extension for Mobula kuhlii cf. eregoodootenkee

Mobulids have been poorly studied, but most are listed by the International Union for the Conservation of Nature as Near Threatened or of greater concern. Here we fill critical know - ledge gaps surrounding reproduction for Mobula kuhlii cf. eregoodootenkee caught at 29° S- 200 km south of their proposed range-off eastern Australia by bather-protection gillnets de - ployed for 6 mo from December 2016. M. kuhlii cf. eregoodootenkee was the second most abundant netted species (all adults: n = 63), with catches peaking in April. There was no sexual segregation, but females (disc width [DW]: 92.5 to 130.0 cm, mean ± SD 112.8 ± 7.8 cm) were significantly larger than males (99.0 to 123.0 cm, 109.4 ± 6.3 cm). Of those caught, 45 died (71% mortality), of which 20 females and 11 males were assessed for reproduction. Nine females were pre-ovulatory and non-gravid with 7 to 23 oocytes in their left ovary, while 11 had 14 to 40 ovarian oocytes and 1 embryo (DW: 7.0 to 21.2 cm) in their left uterus. The diameter of the largest ovarian follicle in gravid females was not correlated with embryo size, indicating ovulation may not occur immediately after parturition. The development of the largest embryo (DW: 21 cm) suggests parturition occurs well above this size. Males had calcified claspers and exhibited large variation in their testes weights, which might imply seasonal fluctuation in sperm production. In addition to extending the distribution of the species and increasing maximum DW to 130 cm, the data provide further evidence of the low reproductive output of M. kuhlii cf. eregoodootenkee, and a need for their effective management

Immature individuals dominate elasmobranch fisheries of the Bali Strait

Elasmobranchs play an important role in the functioning of marine ecosystems and top-down control in food webs. However, overexploitation threatens elasmobranch populations worldwide. Indonesia is currently the leading elasmobranch fishing nation, yet elasmobranch management in Indonesia is challenging because of the paucity of data on elasmobranch fisheries, especially at a species level. This study examined the elasmobranch fisheries of the Bali Strait by describing the species, sex and size composition of the elasmobranch catch landed at a major port in Eastern Java, Indonesia. Data were collected between August 2017 and March 2018 in Muncar. Elasmobranchs were identified to species level and sexed. The disc width and length of 301 rays and the precaudal length and fork length of 1657 sharks were measured. In all, 53 species were identified, many of which are at conservation risk, including species with national and international protection. Vulnerability to fishing gear varied across sex and size of each species, with immature individuals dominating the catch of most species. The findings emphasise the need for improved management of elasmobranchs in Indonesia and could help identify priorities or form strategies. Additional regional and fisheries-specific research is recommended to develop efficient and locally adapted management strategies

Predicting mobulid ray distribution in coastal areas of Lesser Sunda Seascape: Implication for spatial and fisheries management

The Lesser Sunda Seascape (LSS) is considered one of the regions with the largest mobulid fisheries in Indonesia, although their spatial distribution and habitat preference in the LSS is still largely unknown. The goal of the present study was to describe the habitat preference and distribution of the oceanic manta rays, spinetail devil rays, and Chilean devil rays in the coastal area of LSS. We used multiple data sources of mobulid ray sightings and selected significant environmental predictors to execute the maximum entropy model. The model performed well in predicting mobulid ray habitat in the coastal area of LSS and indicated that sea-surface chlorophyll-a (SSC-a), sea-surface temperature (SST), sea-surface salinity (SSS), distance to the 200-m isobath, distance to the 3000-m isobath, and slope were all significant environmental predictors of their distribution. This study confirms that the habitat preference of mobulid rays were in the areas that close to the 200-m isobath and with higher chlorophyll-a concentration as proxy for their prey density. Combining habitat models with fisheries activity records indicated that the areas where these overlaps may represent key mobulid habitats. This study highlights a critical need for species-specific and populations-level management measures for Indonesian mobulid rays, whereas current MPA design has focused on a broad-scale coastal ecosystem management approach, which may have limited effectiveness in practice. This study provides valuable information for the improvement of MPA design and fisheries management tools, through maximum entropy modeling as a powerful means to describe species’ distributions and habitat preference. We recommend that future efforts focus on documenting and incorporating data from large-scale commercial fisheries to improve our knowledge of habitat preference and distribution models in offshore areas and the high seas, and to assess the preference for coastal versus oceanic habitats