Age, growth and reproductive properties of an invasive species Carassius gibelio (Bloch, 1782) (Cyprinidae) in the Ikizcetepeler Dam Lake (Balikesir), Turkey

Background and Purpose: The Prussian carp Carassius gibelio is well known as a hazardous fish species for native fish communities. Ikizcetepeler Dam Lake inhabits some fish species as Cyprinus carpio, Leuciscus cephalus, and Barbus species. The dam lake has major economic importance to the area for both fisheries and drinking water. The reason to select C. gibelio was due to the dominant species in stagnant and slow running waters and possible harmful interactions with native species. Materials and methods: A total of 480 specimens of C. gibelio were monthly collected by gill nets during a 1-year period from Ikizcetepeler Dam Lake. Age was determined from scales. Length-weight relationships, von Bertalanffy equation were used to estimated for growth. Sex were determined by macroscopic observation of gonads. Spawning period of this species was determined according to gonado-somatic index (%). Results: Females and males reached a maximum age groups of VI. Total length was 23.6–31.3 cm in females and 23.0–31.4 cm in males. The male and female ratio was 1:3.52 (M:F) in the favor of females. The Von Bertalanffy growth equations (in length) were found as Lt= 34.89.(1-e–0.11(t+7.66)), Lt= 32.09 (1-e–0.23(t+5.83)) for females and males, respectively. The estimated b values were given as 2.886 and 2.981 for females and males, respectively (b<3). The condition of the fish increased during early summer. Spawning period of this species occured between April and July. Conclusions: With a comparison of the relevant literature, the studied Prussian carp population was characterized by a shorter life span and more rapid growth during the first years of life. These can be considered as typical features of invasive species

Neki biološki parametri trlje kamenjarke (Mullus surmuletus L.) iz Erdemitskog zaljeva, (Sjeverno Egejsko more, Turska)

Growth, sex ratio, and reproduction of striped red mullet (Mullus surmuletus L.) were determined from 520 specimens collected in the northwestern Aegean coast of Turkey from September 2009 to July 2010. Total length ranged from 7.7 to 17.0 cm while weight varied between 3.50 and 58.9 g. According to the length-weight relationship, positive allometry was confirmed for both sexes. The sex ratio was skewed in favour of males (1:1.73). The monthly values of gonadosomatic index (GSI) of females indicated that spawning occurred mainly between April and September with a peak in July. Values of Condition factor (CF) and Hepatosomatic index (HSI) varied between 0.71-1.57 and 0.10-1.43, respectively.Starost, rast i smrtnost trlje kamenjarke, (Mullus surmuletus L.) procijenjene su kod 520 jedinki prikupljenih na sjeverozapadnoj obali Egejskog mora, Erdemitski zaljev u Turskoj od rujna 2009. do srpnja 2010. Ukupna duljina jedinki je u rasponu od 7,7 do 17,0 cm, a masa je kolebala između 3,50 i 58,9 g. Prema dužinsko-težinskom odnosu, ustanovljena je pozitivna alometrija za oba spola. Omjer zastupljenosti spolova bio je u korist mužjaka (1: 1,73). Mjesečne vrijednosti gonadosomatskog indeksa (GSI) za ženke pokazuju da se mrijest obavlja posebice u razdoblju travanj - rujan, sa vrhuncem u srpnju. Vrijednosti kondicijskog faktora (CF) i hepatosomatskog indeksa (HSI) kolebali su između 0.71-1.57 i 0.10-1.43, respektivno