Search

The brown meagre (Sciaena umbra Linnaeus, 1758) population has experienced dramatic population declines, and it was regionally assessed as "Near Threatened" in the Mediterranean. In this study, the current status of brown meagre populations in the Black Sea was evaluated by estimating growth and mortality rates based on age readings from the otolith. All specimens were collected by commercial trammel nets between March 2019 and February 2020 in the Turkish coast of the Black Sea. A total of 324 brown meagre were sampled during the study period, ranging in age from 0 to 26. The peak spawning season of the species was from June to July. The Von Bertalanffy growth parameters of (L8 = 54.15, k = 0.14 yr-1, t0 = -3.11) supports previous studies and suggests that brown meagre is a longlived and slow-growing species. The exploitation ratio of 0.53 for females and 0.47 for males. Life-history features and mortalities indicate that the brown meagre has relatively high fertility but may be undefended to intense fishing pressure. However, the impact of overfishing, pollution and climate change can have increasingly detrimental effects on the overall population size of this population. [ABSTRACT FROM AUTHOR]

The study of fishery biology and population dynamics was conducted for Boops boops collected from the commercial catches of gillnets operated in the Egyptian Mediterranean waters off Alexandria. A total of 880 specimens were sampled from the area between Sidi Kirayr to El-Montazah during the period 2018-2020. The length range varied between 11.0 and 20.0 cm TL with a mean of 13.98±1.19 cm and the total weight varied from 14 to 88 g with a mean total weight of 28.51±6.67 g. The length-weight relationship was computed as W= 0.0119 L2.9453 by using total weights and W= 0.0112 L2.9335 by using gutted weights. The mean condition factor (k) was 0.953±0.029 and the overall sex ratio (M: F) was 1.00:0.49. The von Bertalanffy growth parameters were estimated to be K= 0.38 yr-1, L∞= 27.85 cm and tο= -0.443 yr. The growth performance index (Фˋ) was 2.47. The values of natural (M), fishing (F) and total mortality (Z) were calculated as 0.865, 3.845 and 4.710 yr-1, respectively. The current exploitation ratio (Ecur= 0.816) is high reflecting the high exploitation of this species. The yield per recruit and the relative yield per recruit were also studied and the results confirmed that the stock of B. boops is highly exploited and the management of the pelagic gillnets is required. [ABSTRACT FROM AUTHOR]

Population characteristics and exploitation level of Anabas testudineus from Rudrasagar lake, North-eastern India were studied to understand the dynamics of resource for suggesting necessary strategies for sustainable exploitation. A total of 1187 specimens were sampled to collect the length frequency data from May, 2015 to April, 2016. The length-weight relationship of the fish was found to be Log W = - 4.08+2.9 LogL (r²=0.99). The Von Bertalanffy growth parameters i.e., asymptotic length (L∞)and growth coefficient (K) were estimated using ELEFAN-I as 216.25 mm and 0.78 yr- 1respectively.The growth performance index (φ') was calculated as 4.56. The approximate longevity (Tmax) was estimated as 3.8 years. The total mortality (Z), natural mortality (M) and fishing mortality (F) rates were estimated to be 1.95, 1.54 and 0.41 per year, respectively. The exploitation ratio (E) and exploitation rate (U) were observed to be 0.21 and 0.18, respectively. The results of relative yield-per-recruit (Y'/R) and relative biomass-per-recruit (B'/R) estimated as a function of Lc/L∞ and M/K were 0.46 and 1.95 respectively. The MSY level was estimated at 3.8 tonnes per year at F factor-0.8. Since the current level of exploitation of the species is well below Emax(0.50) and the observed landings are lower than the MSY level, it could be concluded that the fish is presently underexploited in the Lake. Reasonable fishing effort can be increased in order to obtain more yields so as to reach the MSY level and in that way increase the income of the economically poor fishermen communities of North-eastern India. [ABSTRACT FROM AUTHOR]

Abstract: This study provides a contribution to the knowledge on distribution, population structure and dynamics of Lophius budegassa in the North-western Ionian Sea (Eastern Mediterranean Sea) as well as an estimation of its exploitation condition. Data were collected during 23 trawl surveys carried out in spring-summer and autumn from June 1995 to November–December 2006. Specimens were collected between 13 and 745m. No significant trends were shown in the fluctuation of the abundance indices throughout the study period, indicating a stable condition in the stock distributed from the shelf to the upper slope. A decreasing trend with depth was only shown in the density index values. The greatest biomass values were recorded in autumn and the highest incidence of juveniles (TL<14cm) was observed mainly during the spring. The sizes of the specimens in the catch were between 3.5 and 114cm TL. However, the sampled population was mostly made up of specimens smaller than 24cm TL. The females measured between 8 and 114cm TL and the males between 10 and 93cm TL. The sex ratio fluctuated greatly during the investigated period and according to depth. The smallest mature female and male measured 30.5 and 17cm TL, respectively. Mature individuals were collected both in spring and autumn. Their contribution to the sampled population was generally rather negligible, mostly in females. The estimated growth parameters were quite different between sexes with females (L ∞ =68.45cm; k =0.112y−1; t 0 =−1.18y; Φ′=2.72) achieving older size-age than males (L ∞ =60.30cm; k =0.109y−1; t 0 =−1.56y; Φ′=2.60). The age and growth performance examined in this study was confirmed by means of back calculation and, for the first years, by length–frequency analysis. The mortality rate (Z) calculated using the growth parameters derived from the direct age estimation varied between the annual value of 0.54 in 2001 and that of 0.87 in 2000 and 2003. The natural mortality rate (M) was computed using different approaches. In females it was between 0.24 and 0.23 while in males was between 0.25 and 0.24. Adopting two sets of growth parameters for sex combined and the M value of 0.22 and the value of 0.39, two scenarios for fishing mortality rates and exploitation ratios were obtained. Although, the total and fishing mortality rates and exploitation ratios fluctuated throughout the sampling period no significant trends were detected. The E values changed between 0.59 and 0.77 and no significant differences were observed with the two scenarios. A growth overfishing condition was detected for the stock in the North-western Ionian Sea. The exploited stock of L. budegassa in the Ionian Sea mainly consists of juveniles younger than 3–4 years old. Although, spawners are extremely scarce, most probably as a consequence of fishing pressure, the continuity of recruitment seems to be guaranteed by adults distributed in “refuge areas” where trawl fishing does not occur. [Copyright &y& Elsevier]