چكيده انگليسي :
This study was conducted to determine growth parameters, catch and fishing effort trends, stock assessment and Acceptable Biological Catch (ABC) of bony fishes in the Iranian coastal waters of Caspian Sea in the years 2013-2014 and 2014-2015. According to the result, the numbers of beach seines were 124 and 120 and their fishing efforts were observed 44688 and 46299 beach seining, respectively. The total catches (including illegal fishing) were also obtained 17144.3 mt and 16733.2 mt during 2013-2014 and 2014-2015, respectively. The highest proportion of catch was belonged to kutum and golden grey mullet (94.4% and 89.5%, respectively) in two fishing seasons mentioned above.
Growth parameters of kutum were estimated as K=0.19/yr, L∞ = 61.3 cm, t0 = -0.99/yr. The Growth parameters were K=0.18/yr, L∞ = 61.1 cm, t0 = -0.14/yr for golden gray mullet and were K=0.14/yr, L∞ = 70.8 cm, t0 = 0/yr for common carp. Based on catch-at-age data, in the years 2013-2014 and 2014-2015, the total biomass, from the biomass-based cohort analysis were estimated 46900 mt and 41000 mt for kutum and 11550 mt and 12670 mt for golden grey mullet, respectively. The reference points of F0.1 and F35% were 0.41/yr and 0.34/yr for kutum and 0.36/yr and 0.33/yr for golden grey mullet, respectively.
According to catch of species/groups, three main groups can be divided easily. The one–way ANOSIM catch similarity test indicated that coverage rates of different years were homologous and similar, but the coverage rates of different months, regions and periods were not similar. Also, there were significant differences in community composition of fishes in catch of beach seines among three times; three durations; three regions and seasons (in all cases MRPP, p<0.001). During 1996-2000 species Rutilus rutilus, Vimba vimba, Chalcalburnus chalcoides, Aspius aspius,Barbus sp, Salmo trutta caspius and Silurus glani in the years 2000-2005 species/groups shads, Abramis brama and Esox lucius and in the years 2005-2012 species Cyprinus carpio and Stizostedion lucioperca were indicator species. Also, in the west region of the Caspian Sea species/groups Vimba vimba, Chalcalburnu schalcoides, Aspius aspius, Barbus sp, Abramis brama, Stizostedion lucioperca, Esox lucius and Silurus glani; in middle Rutilus frisii kutum, shads and Salmo trutta caspius and in east species/groups mullets, Rutilus rutilus and Cyprinus carpio were identified as indicator species.
Based on available models, the ABCs were estimated as 8250-9750 mt for kutum and 1650-1950 mt for golden grey mullet (with precautionary approach 8250 mt and 1650 mt for kutum and mullet, respectively). For two species, the ABC with a lower and more accurate value based on more information, should be selected for the implementation of a precautionary management approach.
كليدواژه :
درياي خزر , صيد بيولوژيك قابل قبول , ماهيان استخواني , پارامترهاي رشد و مرگ و مير , زيتوده , خوشه بندي
