Search

The current study provides information on deep-water shrimps, Aristaeomorpha foliacea and Aristeus antennatus, which are trawled in the waters of the Mediterranean Sea off Damietta, Egypt, between January 2019 and December 2019. The catch comprised 62.68% of A. foliacea with a range from 16 to 65 mm in carapace length (CL) and 37.32% of A. antennatus with a range from 17 to 57 mm in CL. The overall sex ratio of females to males was 1.00:0.22 for A. foliacea and 1.00:0.47 for A. antennatus. Studying the length-weight relationship (LWR) revealed that A. foliacea and A. antennatus, females, males, and combined sexes, had negative allometric growth. Abdomen weight- total body weight relationship showed that A. antennatus had bigger mean abdomen weight indices than A. foliacea for females, males, and combined sexes. Age was studied based on the Bhattacharya length frequency method and four cohort age groups were predicted for A. antennatus and six cohort age groups for A. foliacea. The second cohort was the dominant age group for both species. For combined sexes, the von Bertalanffy growth parameters were K = 0.244, to = −0.072, and L∞ = 77.109 mm (CL) for A. foliacea, and K = 0.246, to = −0.689, and L∞ = 67.688 mm (CL) for A. antennatus. Total mortality (Z), natural mortality (M) and fishing mortality (F) were calculated as: Z = 0.670, M = 0.423, and F = 0.247 for A. foliacea, and Z = 1.295, M = 0.441, and F = 0.854 for A. antennatus. The exploitation ratio (E) revealed that the stock of A. foliacea was rationally exploited (E = 0.368) and the stock of A. antennatus was over-exploited (E = 0.659). At the current level of explotation, 39.23% of A. foliacea stock biomass and 15.35% of A. antennatus stock biomass were protected. Further studies are recommended to shed lights on the reproductive biology of these deep-water shrimp species.

The current study provides information on deep-water shrimps, Aristaeomorpha foliacea and Aristeus antennatus, which are trawled in the waters of the Mediterranean Sea off Damietta, Egypt, between January 2019 and December 2019. The catch comprised 62.68% of A. foliacea with a range from 16 to 65 mm in carapace length (CL) and 37.32% of A. antennatus with a range from 17 to 57 mm in CL. The overall sex ratio of females to males was 1.00:0.22 for A. foliacea and 1.00:0.47 for A. antennatus. Studying the length-weight relationship (LWR) revealed that A. foliacea and A. antennatus, females, males, and combined sexes, had negative allometric growth. Abdomen weight- total body weight relationship showed that A. antennatus had bigger mean abdomen weight indices than A. foliacea for females, males, and combined sexes. Age was studied based on the Bhattacharya length frequency method and four cohort age groups were predicted for A. antennatus and six cohort age groups for A. foliacea. The second cohort was the dominant age group for both species. For combined sexes, the von Bertalanffy growth parameters were K = 0.244, t o = −0.072, and L ∞ = 77.109 mm (CL) for A. foliacea, and K = 0.246, t o = −0.689, and L ∞ = 67.688 mm (CL) for A. antennatus. Total mortality (Z), natural mortality (M) and fishing mortality (F) were calculated as: Z = 0.670, M = 0.423, and F = 0.247 for A. foliacea, and Z = 1.295, M = 0.441, and F = 0.854 for A. antennatus. The exploitation ratio (E) revealed that the stock of A. foliacea was rationally exploited (E = 0.368) and the stock of A. antennatus was over-exploited (E = 0.659). At the current level of explotation, 39.23% of A. foliacea stock biomass and 15.35% of A. antennatus stock biomass were protected. Further studies are recommended to shed lights on the reproductive biology of these deep-water shrimp species. [ABSTRACT FROM AUTHOR]

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]

The waterway from Chongqing to Yibin in the upper Yangtze River provides strong support for the socioeconomic development in Western China, while it also has a negative influence on the river ecosystem, such as river fragmentation, wetland disconnectivity, fish habitat, and biodiversity. Accurately characterizing the exploitation, economic efficiency, and ecological pressure of the waterway from Chongqing to Yibin is of great significance for the further development of the upper Yangtze River. In this study, based on statistical data from the National Bureau of Statistics of China, the waterway development, economic benefits, and ecological pressure of the waterway from Chongqing to Yibin were evaluated. The sustainability index (SI) was introduced to comprehensively assess the sustainability of waterways using the hierarchical model, which integrates the exploitation ratio (ER), economic efficiency index (EEI), and ecological pressure index (EPI). A relatively low ER (41.04%), a low consistency index (CI, 0.31), a high EEI (9037.18 USA$/gha), and a low EPI (0.33) yielded an SI of 0.70, indicating that the waterway from Chongqing to Yibin in the upper Yangtze River is in a sustainable development stage. Compared with the typical global Golden Inland Waterways, the waterway from Chongqing to Yibin still has great development potential under the prioritizing ecological protection. [ABSTRACT FROM AUTHOR]

Tenualosa ilisha, commonly called Hilsa, is a highly prized species, which has declined in River Brahmaputra, India. The study was carried out for one year and a total of 1,026 individuals were sampled at monthly intervals. In the study, the following growth parameters were observed: asymptotic length (L∞) = 445 mm, growth coefficient (K) = 0.5 year-1, and age at length zero (t0) = -0.5 year-1. Growth performance index (φ) was estimated to be 2.996. Natural mortality rate, total mortality, and fishing mortality was found to be 0.51 year-1, 1.57 year-1, and 1.06 year-1,respectively. Exploitation ratio (E) was found to be 0.675, which indicates that the species is slightly over-exploited. It was seen that length groups that represented the catch in the Indian part of River Brahmaputra comprised fishes of 0–4+ years age. The present study was carried out to assess the population characteristics of this commercially important species from the Indian part of Brahmaputra River, which will contribute towards sustainable fisheries management. [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]

The study of fishery biology of Chrysichthys auratus from Damietta branch, Egypt showed that the population has SL range of 7–20 cm, L′ = 11.85 cm. Males represent 45.90% and females 53.98% of the population. Length–length and length–weight relationships were analyzed for males, females and combined sexes. It was: SL = −0.6231 + 0.8402 TL and LogW = −1.6253 + 2.9832 LogSL for combined sexes, respectively. The highest values of condition factor were obtained in July, August and September for both sexes. The mean value of (K) for males was higher than those of females in all different lengths. Age was assessed by Bhattacharya’s (1967) method from length frequency data to estimate the von Bertalanffy growth parameters (L∞ = 26.53 cm, K = 0.214 and to = −1.569). The individuals of this species live for about 4 years and the first age dominates the population. The growth performance index in length (ФL) and weight (Фwt) was estimated as 2.18 and 1.11, respectively. The mortalities were computed as: Z = 1.44, M = 0.60 and F = 0.84. The exploitation rate was estimated as Ecur = 0.58. Length at first capture (Lc) was 9.66 cm at age 0.54 years. Length at recruitment (Lr) was 8.49 cm and age 0.35 years. It was found that the stock of Chrysichthys auratus in Damietta branch was rationally exploited.

The study of fishery biology of Chrysichthys auratus from Damietta branch, Egypt showed that the population has SL range of 7–20 cm, L ′ = 11.85 cm. Males represent 45.90% and females 53.98% of the population. Length–length and length–weight relationships were analyzed for males, females and combined sexes. It was: SL = −0.6231 + 0.8402 TL and Log W = −1.6253 + 2.9832 Log SL for combined sexes, respectively. The highest values of condition factor were obtained in July, August and September for both sexes. The mean value of ( K ) for males was higher than those of females in all different lengths. Age was assessed by Bhattacharya’s (1967) method from length frequency data to estimate the von Bertalanffy growth parameters ( L ∞ = 26.53 cm, K = 0.214 and t o = −1.569). The individuals of this species live for about 4 years and the first age dominates the population. The growth performance index in length ( Ф L ) and weight ( Ф wt ) was estimated as 2.18 and 1.11, respectively. The mortalities were computed as: Z = 1.44, M = 0.60 and F = 0.84. The exploitation rate was estimated as E cur = 0.58. Length at first capture ( L c ) was 9.66 cm at age 0.54 years. Length at recruitment ( L r ) was 8.49 cm and age 0.35 years. It was found that the stock of Chrysichthys auratus in Damietta branch was rationally exploited. [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]

• The variables are: section shape, fibers type and amount, loading protocol. • FRCM-confined concrete exhibits a multi-stage stress–strain curve. • Fibers strain exploitation ratio and volumetric dilation are evaluated. • FRCM jackets are activated after a certain amount of dilatancy has already occurred. • The envelope curve of the cyclic response is equivalent to the monotonic curve. In this work, the experimental behavior of confined concrete specimens subject to axial cyclic load is analyzed in terms of compressive strength, ductility, stress deterioration, plastic strain development, stiffness deterioration, fibers strain exploitation ratio and volumetric dilation. The following variables were considered, and their influence is discussed along the work: geometry of the cross-section (circular, square and two rectangular ones), fiber material (carbon and glass fibers) and number of layers (up to four for carbon-FRCM jackets), loading protocol (cyclic and monotonic). Results demonstrate that the envelope of the stress–strain curves obtained with cyclic loading coincides with the monotonic curve, for the range of variables analyzed here. Further, the stress–strain curve of FRCM-confined concrete has been modeled according to three different behaviors exhibited in this experimental campaign, being purely softening, softening with plateau, and hardening. [ABSTRACT FROM AUTHOR]