Information on specific nutrients like taurine is important to support a nutritionally balanced diet for marine species such as totoaba Totoaba macdonaldi under culture conditions. Eight isoproteic (50%) and isolipidic (12%) experimental diets were formulated to contain graded levels of taurine (0.23%, 0.45%, 0.91%, 1.28%, 1.76%, 2.20%, 2.72%, 3.01% as‐is) using ethanol‐washed fishmeal (FM) as primary protein source. Green liver, low gallbladder‐somatic index (GBSI), low apparent digestibility coefficient (ADC) of lipid, low erythrocyte turnover, low plasma cholesterol and triglycerides, as well as low visceral fat, were detected in the basal diet (T‐0.23) after 10 weeks. Thermal‐unit growth coefficient (TGC) was best modelled by a five‐parameter saturation kinetic model (5‐SKM, p < .001) with marginal differences (R2 = .13) of juvenile totoaba (initial weight 10.0 ± 1.0 g). Low GBSI (0.095%) was accompanied with low ADC of lipid (78.9%) in the low‐taurine diet (T‐0.23). GBSI and ADC of lipid were best modelled by four‐parameter SKM (4‐SKM, R2=.72 and .87, respectively, p < .001). Plasma cholesterol increased linearly with dietary taurine (R2 = .75, p < .001), while plasma triglycerides increased quadratically (R2 = .53, p < .001), suggesting modulations of lipid metabolism in totoaba. Plasma bilirubin levels increased linearly, and the lowest concentration was found in the basal diet (T‐0.23); however, haematocrit and haemoglobin levels were changed slightly between the treatments. This study demonstrates that supplementation with a low level of taurine (0.45% as‐is) in a washed FM‐based diet can normalize the physiological condition of juvenile totoaba. Green liver, GBSI, ADC of lipid, plasma cholesterol and triglycerides may be informative diagnostic tools for taurine deficiency in totoaba.

Highlight ResearchWastewater in hybrid grouper culture should be maintain before resirculate and dispose to aquatic environment to avoid eutrophication.Seaweed that is used for biofilter must be observed for its suitability, performance and effectivity.Ulva sp. has the best effectiveness to reduce nutrient in wastewater of hybrid grouper aquaculture by absorbing then stored into thallus.Ulva sp. is proven has the best SGR and adaptability in wastewater of hybrid grouper culture.AbstractWastewater generated from hybrid grouper culture needs to be managed to improve water quality before being recirculated, or discharged in the aquatic environment. Seaweed biofilter has been proposed in wastewater treatment technology for marine fish farming. This study aimed at comparing which of these species i.e. Ulva sp., Sargassum sp., Gelidium sp., and Dictyota sp.  work best to absorb nutrient wastewater hybrid grouper culture. This research utilized these seaweed as treatments and controls with three replications using Completely Randomized Design. A statistical analysis was conducted to investigate the significant differences in the nutrient absorptions among various seaweed species by using ANOVA and least significant difference. Non-parametric tests namely Kruskal-Walis, Mann-Whitney, and t-test were used with confidence interval of 95%. The results revealed that Ulva sp. has the best ability to reduce the Nitrogen 80%, while Dictyota able to reduce  Phosphor 88% by Dictyota sp. generated from wastewater of hybrid grouper culture. While the highest absorbtion of Total Kjeldahl Nitrogen (104%) and phosphate (182%) that stored in thallus were performed by Ulva sp. Ulva sp. had the best performance and highest growth rate (1.9% d-1) as biofilter in hybrid grouper cultivation than other species.

Sea cucumbers are marine animals of the Holothuroidea Class that have ecological, health, and socioeconomic benefits. This study aims to determine the structure of the sea cucumber community on Harapan Island and East Penjaliran Island, Kepulauan Seribu National Park, Kepulauan Seribu Regency. Data collection was conducted in January 2020, where each island was divided into two stations, and each station was divided into three substations for data retrieval. The method is a quadratic transect method using a plot measuring 1x1 m. In each square plot, observations were made regarding the type and number of sea cucumbers found and water quality parameters, including salinity, temperature, pH, DO, and total organic matter. Observation parameters include diversity index, uniformity index, frequency, density, important value index, dominance, and sea cucumber distribution index. During the study, species found on Harapan Island include H. atra, H. scabra, H. leucospilota, Bohadschia marmorata, and Stichopus herrmanni. Meanwhile, species found on East Penjaliran Island include H. atra, H. leucospilota, H. coluber, H. pardalis, H. fuscocinerea, H. hilla, Bohadschia marmorata, Stichopus ocellatus, and Stichopus monotuberculatus. The most abundant and predominant species on both islands is Holothuria atra. The average diversity index on Harapan Island falls into the low category, while East Penjaliran Island is classified as medium. The dominance index of both islands is low and has a uniform distribution. Environmental conditions and sea cucumber exploitation affect the structure of sea cucumber communities on both islands.

This research aims to determine the performance and nutrient removal effectivity of seaweeds species, namely Ulva fasciata., Sargassum illicifolium, Gelidium sp., and Dictyota sp. as a biofilter in hybrid grouper aquaculture wastewater at low salinity (14-17 ppt). This study used a Completely Randomized Design with 3 replications. The statistical analysis was carried out by Analysis of Variance continued with the Least Significance Difference test, and the Kruskal-Walis test with the Mann-Whitney analysis, and T-test with a confidence level of 95%. The concentrations of ammonia, nitrate, phosphate, and water quality parameters were observed every 4 days. The seaweeds uptake of N and P in water, and Specific Growth Rate were also observed. The results showed that U. fasciata was able to reduce ammonia by 75.95% and nitrate by 79.53%, which were the highest compared to other treatments, while Dictyota sp. was able to reduce the highest phosphate by 87.5% for 20 days. The highest SGR was achieved by U. fasciata at 1.91 %day-1. The highest N content uptake by seaweeds was 104.4%, and the total P of 182.3% occurred in U. fasciata. Overall, U. fasciata has the highest performance and effectiveness as a biofilter that is able to reduce nutrient waste in low-salinity from grouper aquaculture, for re-circulation or before being discharged into the environment to reduce eutrophication and harmful Algal Blooms (HABs) in aquatic environment. The highest growth rate of U. fasciata can be used as food with highly nutritional and economical value.

As a commercial fish, bullet tuna is constantly caught in purse seine fisheries to provide economic benefits for coastal communities. Biological information such as food preference has to be known due to their sustainability in the future. This research aims to figure out the food composition and preference of bullet tuna (Auxis rochei Risso, 1810) in Prigi Coast, Trenggalek Regency East Java. A total of 294 fish landed by purse seine fishermen have been collected from March up to May 2018. Each individual was measured in its total length and weight, then was dissected for sex determination,  measured the length of intestine, and analyse the stomach content. The data analysis encompasses frequency distribution of total length, relative gut length, frequency of occurrence, index of preponderance, trophic level, niche breadth, and food overlapping. The research result indicates that the main foods of Auxis rochei are fish and crustacean, while the complementary and additional foods were copepod, mollusc, annelid, and debris. Bullet tuna was a carnivorous fish with the trophic level of 3.7 and shows the existence of competition for food resources. Overlapping of feeding occurred in the 19-20 cm long group against the 23-24 cm long group in male fish and the 19-20 cm size group against the 21-22 cm length group in female fish. Bullet tuna use the same feed resources among the size groups of fish, where females use feed over a wider area than males.