International Journal of Aquatic Biology
Volume:9 Issue: 2, Apr 2021

Knowledge on the optimum environmental conditions for a potential aquaculture species is necessary to simulate an artificial setting. The current study investigated the influence of several environmental parameters on the physiology of the mud clam Geloina expansa under natural condition. Highest CIs were recorded during the months of May to August, averaging to 179.79 (±6.47 SE) while the rest of the months averaged only 158.53 (±2.68). Geloina expansa population monthly GSI in Santiago River ranged from 9.64 to 26.51, low values were observed from November to February (12.00±0.36) and from June to July (12.24±2.59). Chlorophyll a concentration and sediment TOM have significant influence in CI variations. DO significantly affected the changes in GSI. These ecophysiological information are vital for the development of aquaculture techniques for G. expansa in northern Philippines.

Replacement of fish meal by cost effective and sustainable plant resources in the formulation of feed for fish is a viable option to alleviate the current crisis in fish feed industries arising due to high cost and non-availability of fish meal. The present research was aimed to evaluate if fermented leaf meal of the aquatic plant Ipomoea aquatica could be used as a fish meal alternative in the formulation of feed for the catfish Heteropneustes fossilis.  Fresh green leaves of I. aquatica were sun dried and finely ground to make Ipomea leaf meal (ILM), which was then fermented for 12 days by the phytase producing bacteria Stenotrophomonas maltophilia strain KUAKSP1 (GenBank Accession No. KY790423) isolated from rumen of goat. Four iso-proteinous, iso-lipidous and iso-energetic feeds were formulated by replacing 0, 25, 50 and 75% of fish meal by the fermented Ipomoea leaf meal (FILM). Protein digestibility of the feeds was evaluated within 12 days in an indoor experiment in glass aquaria and growth performance of the fish was evaluated after 8 weeks rearing in outdoor cement tanks. H. fossilis grew better on FILM supplemented feed as compared to fish meal based control feed. Maximum apparent protein digestibility (APD) of the feed, maximum weight gain (WG) and specific growth rate (SGR) and minimum FCR of the fish were found in 50% replacement group. However, crude protein (CP) and crude lipid (CL) deposition in the muscle of the fish and activity of protease in the gut was higher in 25% replacement group. It is concluded that H. fossilis accepts and grows well on the plant based FILM supplemented feed. For better growth management of the fish, incorporation of FILM in the feed should be restricted to 25 to 50% of fish meal.

Blood cockles, Anadara granosa (Linnaeus, 1758), were collected from the aquaculture grounds (4 stations) of the Selangor coast, Malaysia, and the water quality (water temperature, salinity, dissolved oxygen, turbidity, and chlorophyll a) was measured from September 2011 to June 2013. At all stations, the water temperature fluctuated around 30℃. At station C, located at the mouth of the Selangor River, the salinity was occasionally lower than 20 PSU. However, the salinity of the other stations fluctuated around 30 PSU. In addition, at all stations, the content of dissolved oxygen generally fluctuated around 3 mg.L-1 or above, and the turbidity changed irregularly, sometimes exceeding 300 Forumajin Turbidity Units. The chlorophyll a content fluctuated mainly ranging 4-20 µg.L-1 at all stations, and values above 20 µg.L-1 were occasionally observed. The phytopigment content, a food availability indicator, in the digestive gland tissue of the blood cockles collected from all stations fluctuated ranging 30-770 µg.g-1. However, there was no proportional correlation between phytopigment content in the digestive gland and chlorophyll a content at all stations. Therefore, even in a high chlorophyll a content (over 20 µg.L-1) environment, the accumulated phytopigment in the digestive gland was around 290 µg.g-1. In general, these results indicated the cockles were eating a sufficient amount of foods (organic materials including phytoplankton) all year round during the study period. And, the food availability environment in the aquaculture grounds of the Selangor coast was estimated sufficient to grow the blood cockle.

The purpose of the present study was to investigate the trends in Pharaoh Cuttlefish (Sepia pharaonis) capture fisheries and determine the suitable range for optimized exploitation of S. pharaonis resources in the Iranian part of Persian Gulf and Oman Sea using catch data. The data on Pharaoh Cuttlefish capture fisheries in Iranian southern waters for the twenty-three years was collected and the suitable range for optimized exploitation of S. pharaonis was estimated using the R Software. The average values (95% confidence interval) using the Monte Carlo simulation method for intrinsic population growth rate (r), maximum sustainable yield (MSY), the biomass of maximum sustainable yield (Bmsy) and maximum fishing mortality rate of maximum sustainable yield (Fmsy) were 0.92 (0.73-1.17) per year, 5100 (4200-6200) tons, 1100 (8670-13900) tons, 0.46 (0.36-0.58) per year, respectively. The results showed that the annual catch of S. pharaonis exceeded the maximum sustainable yields and measures should be taken to reduce the number of capture fisheries and fishing effort. With results of the prediction model was observed moving average analysis (MAPE=2.85, MAD=0.10, MSD=0.02) and ARIMA (0, 0, 1) (AIC=9.79, BIC=6.38), are better than other models for a period of five years for modeling annual this species landing. It seems that reducing fishing permits and fishing effort will put the S. pharaonis stock situation in a more favorable condition in the long term and will further benefit the exploiters and the fishing community.

The life history parameters, including age, growth, mortality and recruitment of Yellowfin hind, Cephalopholis hemistiktos were studied in monthly collected samples from January to December 2018. Otolith was used for age determination. Mean size by the end of each year of life was estimated and showed that, the highest annual increment was identified at the end of the first year of life then gradually decreased with increase of fish age. The estimated von Bertalanffy growth parameters were L∞=43.51 cm, K=0.26 per year, t0=-0.74 year. Asymptotic weight W∞ was estimated as 1375.23 g. The length-weight relationship was W=0.0126 L3.0746 with R2=0.94 for both sexes. The instantaneous rates of total mortality and natural mortality were estimated as 0.77 and 0.49 per year, respectively. The gonado-somatic index showed increasing from April to August with a peak in June for both sexes. Size at first capture (Lc)was estimated as 24.30 cm, which was smaller than the mean size at first sexual maturity 25.31 cm. The value of fishing mortality (F=0.28y-1) was slightly higher than the optimum (Fopt=0.25y-1) and smaller than the limit (Flimit=0.33y-1) biological reference point, indicating that species was exploited within sustainable limit. Estimated parameters and the relative yield-per-recruit analysis showed that this species is not over-exploited.

The fishery of Omani sea cucumber, Holothuria scabra, is limited so far to the Mahout Bay in Al Wusta governorate. This fishery supports an uncertain number of fishermen ranging from 100 to 150. This fishery is not well-studied and has no current management program. In order to prepare a management strategy, the government has suspended this fishery for 2 years from March 2018 to March 2021. Apart from presenting a thorough review on the sea cucumber fishery in Oman, the current work presents a detailed analysis of the length–weight relationship, sex ratio, and condition factor of the H. scabra collected from four different areas during the period February-May 2019. Based on the results, the females were longer than males, that is 226±33.4 and 221±37.8 mm, respectively. The overall sex ratio of the entire/pooled sample was 0.49 which was not different from the anticipated theoretical sex ratio of 0.5. The mean Kn and the empirical weight–length equations for the total sample were between 0.12±0.01 and 1.0±0.16, and W=0.03L1.6, respectively.

Considering the role of conjugated linoleic acid (CLA) and soybean lecithin (SBL) in fat digestion, absorption and metabolism as well as stress resistance in aquatic organisms, the current study was a 74-day attempt to investigate the synergistic effects of these two compounds on stress resistance and blood lipoprotein levels of rainbow trout (Oncorhynchus mykiss) weighing 120±5 g. Nine isonitrogenous and isocaloric experimental diets containing 1, 2 and 3% CLA and 2, 3 and 4% soybean lecithin on the basis of the basal control diet (free from CLA and lecithin) were formulated. The fish were exposed to three ascending periods of hypoxic stress (7.5, 15 and 30 min) at the end of culture period. The dissolved oxygen was decreased to 1.96 ppm by injecting nitrogen gas. Significantly higher levels of cortisol and glucose were detected in fish fed on diets having higher levels of SBL (2%) and CLA (3%) at higher stress time improving the resistance to hypoxia stress (P≤0.05). Moreover, levels of triglyceride (TRG), cholesterol (COL), low density lipoprotein (LDL), very low-density lipoprotein (VLDL) and high density lipoprotein (HDL) also increased significantly compared to the control group (P≤0.05). This study reveals that using 2% SBL and 3% CLA in rainbow trout feed can promote resistance to hypoxic stress.

This study investigated the immuno-toxicological effect of the insecticide fipronil at sublethal concentration (10% of LC50) and the potential ameliorative effects of dietary microbial levan in Cyprinus carpio fry. Fish were randomly distributed into five treatments in triplicate for 60 days. Five different treatment groups were: levan control L0F0 (basal feed + 0% levan without exposure to fipronil), pesticide control L0F (basal feed + 0% levan with exposure to fipronil), other three dietary supplemented groups exposed to fipronil with different inclusion levels of levan at 0.25% (L0.25F), 0.50% (L0.50F) and 0.75% (L0.75F), respectively. The results revealed that feeding common carp with 0.75% dietary levan significantly reduced (P<0.05) glutathione-S-transferase and glutathione peroxidase levels in various tissues. Lipid peroxidation and heat shock protein level was significantly (P<0.05) reduced with supplementation of levan at 0.75% compared to other groups. Higher glycogen content was observed in high levan fed groups. Although fipronil exposure had no signficiant effect on lipid profile levels, dietary levan supplementation decreased lipid profile level in the fish exposed to fipronil stress. Total immunoglobulin and myeloperoxidase content of common carp showed an increasing trend with the concomitant increase in the level of levan administration in the diet. Overall, results revlealed that microbial levan at 0.75% in the fipronil induced C. carpio fry mitigated the stress due to its potent nutraceutical properties, thus presenting a promising immunoadditive for aquaculture.