Distribution, population structure and dynamics of the black anglerfish (Lophius budegassa

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• 作者：R. Carlucci ; F. Capezzuto ; P. Maiorano ; L. Sion ; G. D’ ; Onghia
• 关键词：Lophius budegassa ; Anglerfish ; Distribution ; Age ; Growth ; Maturity ; Mortality ; Exploitation ratio
• 刊名：Fisheries Research
• 出版年：2009
• 出版时间：1 January 2009
• 年：2009
• 卷：95
• 期：1
• 页码：76-87
• 全文大小：1239 K

文摘

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 745 m. 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 < 14 cm) was observed mainly during the spring. The sizes of the specimens in the catch were between 3.5 and 114 cm TL. However, the sampled population was mostly made up of specimens smaller than 24 cm TL. The females measured between 8 and 114 cm TL and the males between 10 and 93 cm TL. The sex ratio fluctuated greatly during the investigated period and according to depth. The smallest mature female and male measured 30.5 and 17 cm 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_∞ = 68.45 cm; k = 0.112 y⁻¹; t₀ = −1.18 y; Φ′ = 2.72) achieving older size-age than males (L_∞ = 60.30 cm; k = 0.109 y⁻¹; t₀ = −1.56 y; 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 areasȁd; where trawl fishing does not occur.