Age, growth and mortality of the European Seabass, (Dicentrarchus Labrax) in Bardawil lagoon, North Sinai, Egypt

Age, growth, and mortality of European Seabass (Dicentrarchus labrax) were studied from a small-scaled fishery of Bardawil lagoon, (North Sinai, Egypt). 181 specimens (16.6 to 35 cm total Length and 39.8 to 367.2 g total weight). The relationship between length and weight was W = 0.0054L3.1428. Age was determined by otoliths and age groups I to IV years were observed. Growths in length and weight at the end of each year were calculated. The growth parameters of von Bertalanffy equation were calculated as (L∞ = 48.69 cm, K = 0.1677 yr -1 and t0 = -0.447 yr -1). Growth performance index was calculated (φ = 2.60 for length and 1.25 for weight). Mortality rates were 0.867 yr-1, 0.25 yr1and 0.617 yr-1 for total, natural and fishing mortality, respectively. The currently exploitation rate E = 0.712 yr-1 indicating that, the population of this species is being heavily exploited.

An Experiment on Growth Performance, Specific Growth Rate (SGR) and Feed Conversion Ratio (FCR) of Rohu (Labeo rohita) and Tilapia (Oreochromis niloticus) in Tank Based Intensive Aquaculture System

The growth and survival are considered as the crucial factors that should be taken into consideration in any aquaculture system. The experiment was aimed to evaluate the growth performance and subsequent survival rate of the rohu (Labeo rohita) and tilapia (Oreochromis niloticus). It is important to evaluate the growth responses in relation to Feed Conversion Ratio (FCR) and assessment of the total production of the culture unit. As per the recommended stocking density of 320 fishes/decimal in intensive aquaculture system 8 fry per tank was released to assess the growth performance, survival and production of both rohu (T1) and tilapia (T2). During experimental period, there were three replications for each treatment and feed was supplied at the rate of 12%, 8%, and 4% of the body weight of rohu and 20%, 15%, and 10% of the body weight of tilapia in 1st, 2nd and 3rd month for T1 and T2, respectively. The initial weight of individual tilapia was 7.52±1.81 gm and 14.75±0.19 gm for T1 and T2, respectively. The mean final weight was 44.01±4.03 g for T1 and 139.94±1.29 for T2. The weight gains of fish were 36.49±4.09 gm and 125.19±1.29 gm for T1 and T2, respectively. The mean percent weight gain of tilapia was higher in T2 (1715.05±0.00) than T1 (485.23±0.00). The Specific Growth Rates (SGR) of T1 and T2 were found 4.98±2.28 and 6.26 ±3.83, respectively. There was significant difference (p>0.05) in term of SGR between the treatments. Feed Conversion Ratio (FCR) in T1 and T2 were 2.86±0.14 and 2.23±0.18, respectively. Higher total production was obtained in T2 (1119.52 gm) than T1 (278.19 gm) with 100% survival in both the treatments. The water quality parameters for both of the species were within the suitable range. This study reveals a promising arena for fish culture in tank-based intensive aquaculture system as an efficient way of overcoming the scarcity of water and land. This culture system may be an excellent way of producing fish in a small parcel of land with securing the propitious production and expected outcomes within a limited period of time.

Assessment of Sparus aurata (Gilthead Seabream) stock in Bardawil lagoon, southeast Mediterranean Sea

During present study period from October 2020 to April 2021, gilthead seabream Sparus aurata stock was estimated by using many assessment models to evaluate actual status on Bardawil lagoon. Length at first capture (Lc) was 17.10 and 16.70 cm for females and males respectively, but it was 16.9 cm for all individuals that corresponding age at first capture (tc= 2.49 year). Length at first recruit Lr was 10.70 and 9.70 cm for females and males, respectively, corresponding age tr= 0.77 year. The length at first maturity was Lm= 18.18 cm that corresponding age tm= 2.85 years. Virtual population analysis shows some of intensive capture on S. aurata at its early life’s. Yield per recruit and biomass per recruit tend to collapse as a result of high fishing mortalities. The current study concludes an exact overfishing pressure of S. aurata stock in Bardawil lagoon.