Length-Weight Relationships with Condition Indices of Three Commercial Fish Species Caught by Monofilament Gillnets in the İskenderun Bay, Turkey

Length-Weight Relationships with Condition Indices of Three Commercial Fish Species Caught by Monofilament Gillnets in the Iskenderun Bay, Turkey the stocks of similar species in different times and locations. To cite Length-Weight Relationships with Condition Indices of Three Fish Species by


Introduction
Aquaculture is one of the fastest expanding food production sectors in all around the world, by per annual growth rate of 5,8% during the period 2000-2016 [1]. Hundreds of millions of people in the world depend on artisanal fisheries to survive and live, and artisanal fishing is critically important for not only food, but also for jobs, alimentation, food security, and destitution decline [2].
Over the past years, climate change, habitat degradation and wasteful immoderate fishing have created negative effects on fishing population, and these circumstances have also negatively caused yield sea food according to the Food and Agriculture Organization of the United Nations [3]. Further, these environmental disasters and alien fish migration have caused bioecological changes on native fish in coast of East Mediterranean and Aegean Sea. Artisanal fisheries have been widely affected depending on this situation [4]. Iskenderun bay has been known to have proportionally rich fishing resources compared to other fishing areas of eastern Mediterranean since 1940s [5]. It is well known that the length and weight relationships (LWRs) and Fulton's condition factors (K) are quite useful in determining the fish condition, life history of fish and fish stock [6,7]. They also provide useful equations to determine whether a somatic growth is isometric or allometric growth [8].
Tub gurnard, sand solea and gilthead seabream are economically important for many countries and there are several studies such as embryonic and larval development [9], reproduction [10,11], length and weight relationships and growth [12,10,13,14]. There is little current information and explanation for the Iskenderun bay obtained from LWRs, although it is a reliable calculation method for studied biological characteristics of fish populations in aquatic life. Basically, our objective was to contribute to up to date baseline information on LWRs and K analysis, which could be useful for subsequent bioecological and population-based studies on similar studies done in the eastern Mediterranean region.

Materials and Methods
This investigation was carried out near domestic area of Iskenderun, the sampling are located within 36°36'32.70"N-36°07'44.14" E in Iskenderun bay in Figure 1. All fishes have been identified in the field by Whitehead et al. [15] and scientific names of samples were checked again according to FishBase [16]. Fishes were collected by monofilament gill nets mesh size 28 mm used at depths 10-20 m from Iskenderun bay in September and December 2016. Total length and wet weight were measured to the nearest 0,01 cm using callipers and 0,01 g using digital balance, respectively. Afterwards, fishes were immediately released at their natural habitats. In this study, sampling was made properly as the 4/1 notification regulates commercial fishery by the Ministry of Agriculture and Forestry of Turkey. The length and weight relationships were determined by using the equation W=axL b , where W is total wet weight (g), L is total length (cm), the value a is the y-intercept and the value b is the slope of Ordinary Least Squares regression [17].
The association between length and weight was computed by the determination of coefficient r 2 [8]. Fulton's condition factors (K) were calculated by the formula K=WxL -3 x100 [18]. In order to identify the growth type (isometric or allometric) for all fish species, the value b of LWRs was tested for the deviation from the value of 3,0 by a t-test [8] and the b value of each species was tested by t-test [19]. Data were evaluated by using Microsoft Office Excel 2010 and statistical packages of IBM SPSS 21 were used.

Results and Discussion
A total of 82 specimens belonging to three families were caught from Iskenderun port. The number of samples, minimum and maximum values of length and weight of specimens together with LWRs parameters and K indices of Chelidonichthys lucerna, Pegusa lascaris, Sparus aurata were presented in Table 1. Linear regressions were significant (P<0,001), with the coefficient of determination r 2 values for three fish species. The values 95% confidence limits of b of three fish species were found as 2,001-2,567, 3,294-3,604, 3,106-3,498.

Conclusion
The value of parameter b was estimated at 2,28 for C. lucerna, 3,45 for P. lascaris and 3,30 for S. aurata. This data is compatible with the fact that the value of b must vary from 2 to 4 via Tesch [20]. Additionally, the value of b, as a characteristic of the species, is generally stable throughout the year [21]. All regressions were highly significant (P<0,001), and the values of coefficient r 2 ranged from 0,90 (P. lascaris) to 0,95 (S. aurata), and the value of r 2 for C. lucerna was determined as 0,91. A species with the value of b different from 3 is said to have allometric growth; otherwise, the type of the growth is isometric.
In this study, negative allometric growth was determined for C. lucerna, since its b value was less than 3. In a similar work carried out in the west cost of Portugal, the growth for tub gurnard was determined to be negative allometric (P<0,05) [12,13].
We determine a positive allometry for the growth of P. lascaris as well as Tsagarakis et al. [22] have measured for sand soles sampled from Black Sea, Sinop (P<0,001). Computations show that S. aurata has a positive allometric growth in this study, whereas gilthead seabream showed negative allometric growth in another study (P<0,05), [13].  The length-weight relationship in fish is affected by a number of factors including season, habitat, sexual maturity, diet regimen, health, and conservation techniques [20]. The condition factor K was determined as 0,72 for P. lascaris, 2,00 for S. aurata, and 1,05 for C. lucerna (see Table 1.), which increases during the reproductive cycle of the most of species, decreasing during the spawning season and increasing after that, and well matched with their reproductive cycle [16].

Statement of Conflict of Interest
Author has declared no conflict of interest.