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.

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.

Abstract:The present study conducted in Fish Reproduction & Spawning Lab., NIOF, Alexandria, Egypt. European sea bass Dicentrarchus labrax newly hatched larvae from 8 dph to the 40 dph was reared according to (Süzer et al., 2011). The 6 tanks was green water with N. salina Algal count not less than 300000 cell/ml. The experimental treatments using green water using N. salina as positive control (G), green water plus marine probiotic bacteria (G+MP) and green water plus synbiotic (G+S).4 hours enriched rotifers Brachionus plicatilis started from the 7 th dph until the 14 th dph, the beginning of cofeeding on 6 hours enriched Artemia fransiscana (GSL) nauplii started and rotifers reduction started in the 18 th dph and stopped from the 20 th dph and artemia napulii fed alone until the 25 th dph, 25dph larvae started feeding on artemia metanauplii and cofeeding with Orange® P 1/2 Small microdiets with 100-200 micron to 35dph. From the 35 th dph artemia metanapulii stopped and larvae fed only on O.range® until the end of the experiment (the 40 th dph). The treatments were green water using Nanochlorapsis salina algae (G), greenwater plus marine Bacillus subtilis HS1 Probiotic bacteria (G+MP) and greenwater plus synbiotic (G+S) in 30 l tanks in duplicates. Microbiological measurements were performed in water samples in every larvae critical stage (7, 14, 21, 25, 35 and 40dph) for colony forming unit (CFU) of total bacterial count, Vibrio, Staphylococus, Aeromonas and Bacillus. Also water quality measurements were performed in the beginning of the experiment in 2 pm and in the same time in the 7, 14, 21, 28, 35 and 40 dph newly hatched larvae tanks. Finally, the results of the 40dph early weaned larvae showed significantly (p<0.05) higher final total length achieved by (G+MP) followed by (G+S) and the lower significant (p<0.05) recorded by (G) treatment. The bacterial counts of the Aeromonas not detected in all treatments, the other bacterial counts showed promising results of (G+MP) and (G+S) than (G) treatments in both inhibiting potentially pathogenic bacteria counts and also in improving the potentially useful bacterial counts.