عنوان مقاله [English]
نویسندگان [English]چکیده [English]
We selected five sampling sites to identify Goby species in the southern Caspian Sea (Guilan province). Bottom trawling was used for the sampling from September 1999 to August 2000. Results showed that the Goby specimens in this area belong to the genus Neogobius and Benthophilus. Identification of the species was carried out by Dr. Coad of the Natural History Museum of Canada. Four species from the Neogobius were identified which were as follows: N. caspius, N.fluviatilis, N. melanostomus and N. kessleri. Two species from the genus Benthophilus were identified as B. stellatus and B. ctenolepidus., As for the biological characteristics of the N. caspius, we found that the average total length (TL) of N. caspius samples was 112.98±19.87mm and their average total weight (TW) was 16.39±6.21 grams. Age composition of the samples showed the fish were in age groups 1-3 years old with the two years old fish being dominant. Average absolute fecundity was 1031.91±598 eggs. Food items of the species based on the gut content were from Carididae, Mysidae, Cumacae, Hypaniula, Chironomidae, Nematoda, Abra, Gammaridae, Mytilaster, Bivalves and fish. Evidence of carnivore behavior was observed in some specimens. The most frequent food items were Cumacae, Abra, and Gammaridae respectively. The Cumacae was mostly observed in the gut of 1 and 2 years old specimens while Abra was observed mostly in the gut content of 3 years old specimens. Condition factor and feeding rate were highest in the 1 year old class. We found that with increase in fish age, these parameters declined. However, again at the age of 3, the parameters showed a slight increase. Relative gut length also increased from 0.97 in the age class 0+ to 1.38 in the age class 3+.