LENGTH–WEIGHT RELATIONS FOR 29 FISH SPECIES FROM HOMA LAGOON, AEGEAN SEA, TURKEY

used to provide information on the condition of fish and determine whether somatic growth was isometric or allometric (Le Cren 1951, Tesch 1971, Ricker 1975). LW relations of fish are important because they allow: • to estimate the condition of fish, • to calculate biomass from the length values, • to determine weight-at-age and convert growth-inlength equations to growth-in-weight ones, and • to make interregional comparisons of life histories of certain species (Gonçalves et al. 1997, Froese and Pauly 1998, Moutopoulos and Stergiou 2002, Dulčić and Glamuzina 2006). This study reports the parameters of the length–weight relations for 29 fish species collected from Homa Lagoon, Izmir Bay, Aegean Sea of Turkey: Anguilla anguilla (Linnaeus, 1758); Atherina hepsetus Linnaeus, 1758; Atherina boyeri Risso, 1810; Belone belone (Linnaeus, 1761); Blennius ocellaris Linnaeus, 1758; Sardina pilchardus (Walbaum, 1792); Aphanius fasciatus (Valenciennes, 1821); Engraulis encrasicolus (Linnaeus, 1758); Gobius niger Linnaeus, 1758; Pomatoschistus marmoratus (Risso, 1810); Pomatoschistus minutus (Pallas, 1770); Zosterisessor ophiocephalus (Pallas, 1814); Dicentrarchus labrax (Linnaeus, 1758); Chelon labrasus (Risso, 1827); Liza aurata (Risso, 1810); Liza ramada ACTA ICHTHYOLOGICA ET PISCATORIA (2014) 44 (3): 249–257 DOI: 10.3750/AIP2014.44.3.09

(Risso, 1827); Liza saliens (Risso, 1810) (Linnaeus, 1758); Sarpa salpa (Linnaeus, 1758); Sparus aurata Linnaeus, 1758; Platichthys flesus (Linnaeus, 1758); Solea solea (Linnaeus, 1758). Also length-weight relations for five fish species (Anguilla anguilla, Atherina hepsetus, Pomatoschistus marmoratus, Pomatoschistus minutus, and Platichthys flesus) are presented for the first time from Homa Lagoon in the Turkish Aegean Sea. We believe that the results of the presently reported study can be applied to fisheries management of the Homa Lagoon and also Izmir Bay. Study area. The Homa Lagoon (38º30′-38º35′N, 26º48′-26º53′E) is situated in the north-eastern part of Izmir Bay, in the Menemen District 42 km away from the centre of the Izmir Metropolitan Municipality. The lagoon covers an area of 1200 ha, being 7.4 km long and 3 km wide. Its maximum depth is 1.8 m, but many areas are shallow (0.5-1 m). The lagoon is separated from the see by a narrow sandspit. There are 6 canals allowing the water exchange between the sea and the lagoon. The widest canal is outfitted with a barrier trap designed to catch fish. For a detailed map of the lagoon see Bayhan and Acarli (2006). Surface water temperature varies from 28ºC in September to -2 ºC in December with a yearly mean of 16ºC. Mean annual salinity is 31.9‰ with the highest of 44.4‰ and the lowest of 27‰ in November and April, respectively. The lagoon supports important commercial fisheries, including mullets (especially Liza saliens and Mugil cephalus), gilthead sea bream (Sparus aurata), sea bass (Dicentrarchus labrax), ell (Anguilla anguilla), and sole (Solea solea) in particular (Alpbaz and Kınacıgil 1988, Bayhan and Acarli 2006, Acarlı et al. 2009). Data collection. Monthly field studies were performed between February 2009 and March 2010. Samplings were made using four different fishing gears: beach seine, fyke nets, barrier trap, and trammel nets of different mesh size (Table 1). The beach seine was used at day light with 6-7 hauls a day (monthly for a year). Fyke nets were set at dusk and picked up at dawn with a soak time of 10-14 h a day of every month. Barrier trap is generally set between the lagoon and the sea with a rectangular trap chamber composed of reed fences including the closure of canal with reed fences on both sides. Fish swim through a V-shape entrance into the trap and pass through a few sections as far as the final chambers, from where they are taken our with dip nets. As Katselis et al. (2003) reported, one of the most important types of exploitation is to use of barrier traps to catch fish during their seasonal or ontogenic offshore migration. The lagoon is an important nursery area and constitutes the fish feeding ground and therefore the local fishery benefits from fish migration related to feeding and reproduction. The sampling, using the barrier trap, was occasional and was performed either in the day light or overnight, between December and June (The trap was opened in December and closed in early June). Trammel nets were used overnight for a day, monthly. Fish were scared back into the nets and collected after being entangled. Data analysis. Specimens caught were identified to species level, measured to the nearest 0.1 cm (total length, TL), and wet-weighed (total weight, TW) to the nearest 1 g. The relation was established using linear regression analysis, TW vs. TL (log-transformed): Log(TW) = log(a) + (b)log(TL) where a is the intercept of the regression curve (coefficient related to body form) and b is the regression coefficient (exponent indicating isometric growth when equal to 3). The significance of the regression was assessed by ANOVA and the b-value for each species was tested to be significantly different from the isometric growth (b = 3) (Sokal andRohlf 1981, Verdiell-Cubedo et al. 2006). All statistical analyses were evaluated at P < 0.05 significance level.
A total of 2690 individuals was sampled during the study period. The LW relations of 29 fish species of 15 families are given in Table 2. Mugilidae and Sparidae were the most abundant families. Linear regressions were significant for all studied species (P < 0.05). The sample size ranged from 178 Aphanius fasciatus to 37 individuals for Syngnathus typhle.

Fishing gear Description
Beach seine Wings length 25 m, wing height 1.5 m, bag length 5 m, mouth width 3 m, mouth height 1.5 m

Fyke nets
Equipped with 3 funnels and 7 hoops, the first of which is D-shape; Every operation included 50 fyke nets of the same characteristics which were tied to one another used in a serial line; Mesh size of 12 mm were used to construct the netting; The leading net was 3 m long between the two fyke nets with a 12 mm mesh size Barrier trap Trap entrance with V-shape passage; Composed of few small chambers tied to each other with V-shape passages; In Homa lagoon, the barrier trap is opened in December and closed in early June

Trammel nets
Each 300-m long; with 3 different mesh sizes (25, 28, and 30 mm) with variable bar lengths inside nets; Hanging ratio (E) was 0.50 for 100 m length of net  Table 2 Length-weight relations of fish species from Homa lagoon $ Statistically significant; + juveniles; N = sample size, a = intercept, b = regression coefficient, SD = standard deviation, SE = standard error, r 2 = coefficient of determination.  Table 3 Length-weight relations of fish species from Aegean Sea     Table 3 cont. $ Fork length was used instead f total length; N = sample size, a = intercept, b = regression coefficient.

Family
All allometric coefficients (b) were within the expected range from 2 to 4 (Bagenal andTesch 1978, Koutrakis andTsikliras 2003 The coefficients of determination (r 2 ) ranged between 0.831 for Chelon labrasus and 0.999 for eleven species (Table 2), corresponding to a mean value of 0.930 (±0.017 SE).
L-W relations in fish are influenced by various parameters such as habitat, season, degree of stomach fullness, gonad maturity, sex, health, preservation techniques, and differences (Tesch 1971, Dulčić and Kraljević 1996, Wootton 1998, Verdiell-Cubedo 2006. Therefore, fish species of b value in the same area can change at different year or period. In this study, L-W parameters of five species (i.e., Anguilla anguilla, Atherina hepsetus, Pomatoschistus marmoratus, Pomatoschistus minutus, and Platichthys flesus were determined for the first time in the Aegean Sea (Table 3). In addition, the b value of Blennius ocellaris, Aphanius fasciatus, Engraulis encrasicolus, Dicentrarchus labrax, Liza aurata, Liza saliens Mullus surmuletus, Diplodus vulgaris, and Lithognathus mormyrus were estimated higher than in other studies for Aegean Sea. Similar or lower results for b value were found for other species in Table 3. Overall, the LW relations of the fish caught in lagoons are different between the Mediterranean and the Aegean Sea. The reason for this is the diversity of the fishing methods. In the Mediterranean lagoons such as Klisova and Papas in western Greece (Moutopoulos et al. 2011), Mar Menor Lagoon in Spain (Verdiell-Cubedo et al. 2006), the only one type of the fishing gear used was beach seine. In the presently reported study, four different fishing gear types were used (fyke nets, three trammel nets with different mesh sizes, barrier trap with V shape entrance, and beach seine). When b value is compared between Greek lagoons and Homa Lagoon, the b values of Mugilidae species in Klisova and Papas lagoons are higher than those reported presently by us. On the other hand, in both above-mentioned lagoons the b value for Diplodus annularis was lower than the one form the presently reported study. The b values of some fish species from the Mar Menor Lagoon (Engraulis encrasicolus, Gobius niger, Liza aurata, Liza ramada, Liza saliens, Lithognathus mormyrus, and Sarpa salpa), reported by Verdiell-Cubedo et al. (2006) were lower than our respective results. However some of the fish species as Pomatoschistus marmoratus, Chelon labrasus, Mugil cephalus, and Sparus aurata in Mar Menor Lagoon were higher than those presently reported from Homa Lagoon. Such differences in b values can be associated with one or a combination of factors such as: the differences in the number of specimens examined, the area or/and season effects, the distinctions in the observed length ranges of the specimens caught, as well as the duration of the sampling periods (Moutopoulos and Stergiou 2002).