Summary Length–weight relationships were estimated for 11 elasmobranch and 51 teleost fish species caught in Izmir Bay, Turkey. Sampling was carried out from June 2005 to May 2006 at monthly intervals using a bottom trawl net. The mean b‐value was calculated as 3.10 (SE = ±0.03) and only three species were out of range between 2.5 and 3.5.

Specimens of European hake were collected by a traditional demersal trawl between July 2004 and June 2007 from İzmir Bay, Central Aegean Sea. A total of 2108 individuals were sampled during the study and the female: male sex ratio of the stock was 1:0.89. The length–weight relationship was W = 0.00341L3.24 (R2 = 0.994) for all individuals. A high gonadosomatic index was evident over most of the year but it was minimal from August to October. The estimated age composition was 1–5 years; the length and weight at infinity were calculated as L∞ = 54.53 cm and W∞ = 1455.77 g respectively. In addition, growth coefficient was found to be k = 0.315 y−1 and to = −0.223 y (R2 = 0.99). Total mortality ratio of the stock was calculated as Z = 1.539 y−1, while natural and fishing based mortality ratio were estimated as M = 0.579 y−1 and F = 0.959 y−1 respectively, with the exploitation ratio (E) of the stock estimated to be 0.624.

Summary A total of 1527 specimens of poor cod, Trisopterus minutus, was collected by trawl fishing between April 2001 and March 2002 from the İzmir Bay (Middle Aegean Sea). Fish size ranged from 10.6 cm total length (TL, minimum) in September to 24.8 cm TL in April. Of the sampled population 53% were males and 41% females (sex ratio female : male = 1 : 1.3). Length–weight relationships were determined for males, females and combined sexes as W = 0.007L3.16, W = 0.009L3.04 and W = 0.007L3.14 respectively.

The dataset of the study consists of total length, fork length, head girth, maximum girth and weight measurements of 136 bluefish. The relationship between the total length and fork length of the product was TL=1.1348×FL0.8184; the relationship between the total length and weight was W=0.0103×L 2.97. The relationships between the total length and head girth and between the total length and maximum girth of the sample were linear: the relationship of the total length and head girth was Ggill=0.5092×TL0.0874; the relationship of the total length and maximum girth was Gmax=0.5989×TL0.8540. The statistical relationship between length and girth was used to obtain a theoretical gillnet selectivity equation for the species. In conclusion, a relationship of S(l)=Φ[(CGgill)/0.4952]×[1Φ((CGmax)/0.4255)] was determined between the stretched size of the mesh used in bluefish fishing and the catch rate. Using this equation, and considering the legal length and length at first maturity, the minimum mesh size of the gillnet for sustainable fishery was determined.

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