Iranian Journal of Ichthyology
Volume:6 Issue: 4, Dec 2019

This study examined the changes in Mean Trophic Level (MTL) and Fishing in Balance index (FiB) of the Iranian fisheries harvested from the Persian Gulf and Oman Sea during the period from 1997 to 2016. The MTL was initially increased significantly followed by a consistent decline for two decades (R=0.45, P<0.05). The MTL demonstrated a declining process that might be attributed to over exploitation of fish stocks. The FiB index also illustrated an intermittent process and positive values from 1998 to 2016, that could be related to the unbalanced condition in this ecosystem (R=0.92, P<0.05). The analysis and interpretation of the MTL and FiB patterns suggest that the fish stocks in the regional Iranian waters of the Persian Gulf and Oman Sea have been over-exploited, which might have been due to fishing down (FD) in this area. The results revealed that the fishery management strategies which were implemented during this period had not been appropriate and should be replaced with new policies and regulations based on the stock assessment, fishing effort, and other effective factors

 The Caspian stellate tadpole-goby, Benthophilus leobergius is endemic to for the Caspian Sea. In Iranian waters of the Caspian Sea, however, little is known about its life history. To address this, life history characteristics were examined in 256 specimens collected from the southeastern Caspian Sea, northern part of the Miankaleh Wildlife Refuge. The maximum observed age was 2+ years for both sexes. The sex ratio of males to females was 1:1.70. Estimated length-weight relationship was TL=0.0088TW3.289 for males, TL= 0.0099TW3.191 for females, and TL=0.0086TW3.270 for the combined sexes. Egg diameter ranged from 0.8 to 1.8 mm with the mean of 1.259±0.50 mm. Mean absolute and relative fecundities were 2117±1243 eggs/female, and 130±77 eggs·g-1 body weight, respectively. Absolute fecundity and egg diameter were found to increase significantly with increasing fish size, whereas relative fecundity decreased significantly with total body weight.

The length-weight relationship and condition factor of eight fish species from three basins in Iran were estimated. All specimens were captured from May 2010 to August 2017. Total length and total weight ranged 2.2-39.1cm and 0.14-656g, respectively. The bvalue was calculated using W=aL b , which ranged from 2.53 (Paraschistura turcmenica) to 3.2 (Garra rufa), and condition factor was 0.89 (P. turcmenica) to 1.53 (G. rossica). This study provided LWR and condition factor of Chondrostoma cyri for the first time from Iranian inland waters.

To study the growth parameters of long fin banner fish, Heniochus acuminatus, samples were monthly collected from the trawl catches of five major fish landing centers (Pondicherry, Cuddalore, Parangipettai, Karaikkal, and Nagapattinam) of the southeast coast of India during January to December 2015. A total of 475 longfin bannerfish (222 males and 253 females), ranging in size from 6.0-15.2cm for males and 5.6-15.7cm for females were collected. The total body weight of male and female were ranged from 11.06-25.34g and 10.90-27.15g, respectively. The b-value estimated for male (3.006) was greater than 3 (isometric) and for female (2.809) was less than 3 (slightly negative allometric). The correlation coefficient values (r) for male (0.984) and for female (0.995) was highly significant, with a high degree of the positive correlation between total body length and weight. The relative condition factor (Kn) values were found higher in females than males during various seasons. The asymptotic length Lα values obtained using various methods for females ranged from 16.8 to 18.3cm (TL) and similarly, for males, it ranged from 16.77 and 176.4cm (TL). Most appropriate values of growth rate (K) for males and females were 1.20 yr-1 and 1.80 yr-1 , respectively. The estimated t0 for males and females were -0.191 and - 0.166, respectively. The growth parameters obtained during the present study will be used for stock assessment of this species.

The effect of different water exchange regimes on the growth and survival of koi carp, Cyprinus carpio in tanks provided with the supply of exogenous zooplankton as the food was investigated. Fish larvae (0.15±0.012g) were stocked in outdoor concrete tanks at 0.5 fish/l (T1 and T2); 1.0 fish/l (T3 and T4); and 1.5 fish/l (T5 and T6) and cultured for three months. The water exchange rate was 10% once daily in T1, T3 and T5 and twice daily in T2, T4 and T6. Values of dissolved oxygen were highest in T2, followed by T4, T1, T6, T3 and T5. The T5 treatment showed the highest concentrations of conductivity, NH4-N, NO2-N, NO3-N, PO4-P, and bicarbonate alkalinity, which were significantly higher than the other treatments. The final body weight of C. carpio ranged from 4.01 to 8.22g in the different treatments. At harvest, maximum weight gain was achieved in the T2, followed by T4, T1, T6, T3 and T5 in descending order. There was a significant difference in the survival of koi carp among the treatments, ranging from 56.43% (T5) to 96.32% (T2). The percentage and number of fish exceeding a total weight of 5g were estimated from the size-frequency distribution at the end of the study and was significantly higher in T6 (P<0.05) than other treatments. From the present study, a daily water exchange of 20% could support higher stocking densities of koi carp in tanks and result in high productivity, measured in terms of the number of marketable fish.

Four isocaloric diets were formulated to contain 0 (control), 2, 4 and 8% of Wood betony (WB), Stachys lavandulifolia hydroalcoholic extract in a 56-days feeding trial on African cichlid, Sciaenochromis fryeri. The regression analysis of growth performance indices indicated that the best performance parameters including specific growth rate and weight gain were obtained in 3.9% WB in the diet. Total bacterial counts in the fish gut were reduced significantly from 20.50±4.22 (×103 Colony-Forming Unit; cfu g-1 ) in the control to 9.30±0.71, 3.60±0.98 and 3.10±0.80 (×103 cfu g-1 ) group of fish fed on 2, 4 and 8% WB, respectively (P<0.05). No significant change was observed in the number of lactic acid bacteria and it was in the range of 0.80-1.30 (×103 cfu g-1 ). Evaluation of the mid-intestine morphology of fish fed on the graded levels of WB was done. Although fold and enterocyte heights were significantly increased in the fish fed on WB-enriched food in comparison to the control, the intestine diameters and microvilli lengths were not affected. This study indicated that hydroethanolic extract of WB can be considered as a supplement in fish diet to improve growth and some physiological aspects of the cichlid.

Understanding habitat preference is important in many terms such as management of fish populations, assessment of river health, river restoration, etc. In this regard, we chose Capoeta razii, one of the most abundant species in the Caspian Sea rivers, to study its habitat preferences in different ages. As pilot, Zarem Stream, a main tributary of Tajan River with low pressures and high habitat diversity, was selected. After collecting fish species in different random points, the environmental variables in the sampled areas were measured immediately after sampling. Habitat preferences analysis for different ages of this species showed that each age has almost own specific preference in terms of flow velocity, depth as well as abiotic and biotic substrate