Iranian Journal of Fisheries Sciences
Year:2009 | Volume:8 | Issue:2|Papers Count:10

In the present study, age, growth, length-weight relationship and reproduction were investigated in gilthead seabream (Sparus aurata L., 1758) collected from Beymelek Lagoon (Antalya, Turkey) between February 2006 and July 2007. The age, total length and weight of samples ranged from 0+ to 4 years, 10.6 to 35.5cm, and 18 to 928g, respectively. Growth was described by the standard form of the von Bertalanffy growth equation and the estimated parameters were L¥ = 44.6cm, k = 0.394yr-1 and t0 = -1.331yr. Length-weight relationship was determined as W=0.0174TL2.9769 (R2=0.965), and weight increased with size isometrically (b = 2.9769) for all fish. Sex inversion occurred mainly at 26 cm in total length and females reached sexual maturity at 28.5 cm. The spawning period was from December to February, while the gamete emission peaked in December.

Age structure of the Caspian Sea anchovy kilka, Clupeonella engrauliformis, was estimated for the first time by back-calculation methods. Otolith growth and the rate of increment in anchovy kilka were examined to determine whether otoliths could be used to back calculate body sizes at various life stages. Sampling was carried out on commercial fishing vessels board along the Iranian coast in 2007. The age structure of the samples ranged from 2 to 7 years old which was dominated by the third year class (38.6%). The largest fish measured was 137.2mm fork length. The relationship between fork length (FL) and otolith radius (OR) was described by the following equation: FL=13.77+ 82.78*OR (r2=0.92). Three proportional back-calculation methods, Fraser-Lee, Whitney & Carlander and Dahl-Lea models, were compared by using data sets of anchovy kilka otoliths, and we validated back calculation by comparing them with observed lengths. Back calculated lengths generally corresponded well with observed lengths in anchovy kilka age classes. Variance of the back calculated length data obtained from three models indicated no significant difference (P>0.05).

Common carp (Cyprinus carpio) represents one of the most economically important fish species in the Caspian Sea. In this study, growth and mortality parameters among population of common carp was investigated. Sampling was carried out weekly, using beach seine in the south of the Caspian Sea from October 2006 to September 2007. As a contribution to elaborating management programs for common carp, the age and growth of this species was calculated via scale, growth parameters and mortality rate by length frequency data obtained from commercial fishing and research beach seines. Ten age groups were recorded from 1+ to 10+ years old, being dominated by 4 and 5 year-old fish. The growth parameters based on scale reading data by length at age analysis were FL¥= 71.52cm and K = 0.16 per year for total population, FL¥= 70.54cm and K = 0.15 per year for males, and FL¥= 72.00 cm and K = 0.16 per year for females, whereas by length frequency analysis, these values were estimated as FL¥ equals 72.0, 69.3 and 73.0cm and K equals 0.18, 0.15 and 0.18 per year for total population, males and females, respectively. The total, natural and fishing mortality rates were 0.71, 0.29 and 0.42 per year, respectively.

There have been recent changes in the Caspian Sea ecosystem, such as those due to changes in sea level or those caused by the invasive ctenophore, Mnemiopsis leidyi. It is believed that these changes had significant impacts on the absolute and relative abundance of the commercially important anchovy kilka (Clupeonella engrauliformis) and common kilka (C. cultriventris caspia) leading to decline in the former and increase in the latter species in the Iranian waters. Consequently, more rigorous management is required. The mixed-species yield-per-recruit was applied to the Iranian conical lift-net. This study showed that the pooled fishing mortality at F40% was 0.70 yr-1 which is higher than fishing mortality of main species of anchovy kilka, but lower than the pooled fishing mortality at F0.1 (0.75 yr-1). The ABC under the best information available, at pooled species reference points for two species of anchovy and common kilkas, was estimated to be 8260mt. An analogous goal in a multispecies situation would be fishing at a fishing level, denoted Fws, such that the fishing rate for the weakest stock (in this case; anchovy kilka) does not exceed its F40% rate. Under this harvest strategy at F40% for anchovy kilka, it is suggested that the ABC of pooled species of anchovy and common kilkas was estimated 7920mt to be selected in kilka fishery in Iranian waters.

Fish sauce is a fermented product which is used in south Asian countries. In the present study, Caspian Kilka was used to produce the sauce, using either cooked or raw fish subjected to four different treatments: 1) traditional method, where fish and salt were used; 2) an enzymatic method, where fish, salt and proteolytic enzymes, including Protamex and Flavourzyme (Novo Nordisc Co., Bagsvaerd, Denmark), were used; 3) a microbial method, where fish, salt, and Bacillus and Pediococcus species were used; and 4) a combination of the enzyme and microbial methods. Fermentation of the ingredients was carried out in 400cc bottles for a period of 6 months with microbiological and chemical tests at intervals of one week and then one month. The results of molds, yeast, and aflatoxin detection tests were negative. The total bacterial count ranged between log 2.1 and 6.18. Chemical tests included TVN and pH. pH of the final products ranged from 6.5 to 7.0. The speed of fermentation as determined by examining the bottles every two or three days was as follows: Traditional< Microbial<Enzymatic = Enzymatic+Microbial Method. However different treatments could be used to speed up the fermentation, but the traditional method is considered to be better as the quality is concerned.

In the present study, age, growth and reproduction of Carassius auratus were investigated in the Alma-Gol and Ala-Gol (northern Iran) from September 2000 to August 2002. Among the total of 1450 specimens, the estimated ages ranged from 0+ to 8+ years. C. auratus showed an allometric growth, negatively in Alma-Gol and positively in Ala-Gol. The von Bertalanffy growth curves were fitted to mean total lengths at age, resulted as Ltmales=183.33(1-e-0.31(t+1.05)) and Ltfemale=245.66(1-e-0.19(t+1.21)) for Alma-Gol population and Ltmale=224.79(1-e-0.24(t+0.83)) and Ltfemale=242.80(1-e-0.23(t+0.80)) for Ala-Gol population. The value of f’ index varied from 9.25 to 9.51. The unbalanced sex ratio of males to females was 1:10 and 1:12.7 in Alma-Gol and Ala-Gol, respectively. The reproductive period for this species in these particular areas was February, March and April and the maximum recorded GSI was 2.19 and 2.17 for males and 10.37 and 10.49 for females in Alma-Gol and Ala-Gol, respectively. The linear relationship between absolute fecundity and total weight was more suitable for expressing the fecundity-weight relationship for both populations as estimated: Fec.Alma-Gol= 4120.56+ 62.62W and Fec.Ala-Gol= 3832.83+ 68.67W.

Bioaccumulation of heavy metals including Cd, Pb, Cu and Zn in muscle, gill, liver, kidney and stomach in Acipencer persicus was studied. Fish were collected from the ‘Iranian fishery zone 1’ located between Astara and Kiyahshahr. Samples (n=25) were collected from five stations in the study area during the autumn catch season in 2001. Samples were analyzed by wet digestion with hydrogen peroxide and nitric acid. Analyses were testified using spike method. A sample of bovine liver (CRM 185R) was tested to ascertain reliability of analyses. Digested samples were analyzed using Flame Atomic Absorption Spectrophotometer. The bioaccumulation pattern for Zn in different tissues studied was stomach>liver> kidney> gills>muscle tissue. The mean concentration of Zn in the stomach was 136.6±10.70mg g-1 dry weight. Cu with the maximum concentration of 39.71±8.85mg g-1 dry weight in liver showed a bioaccumulation pattern of liver>kidney>stomach>gills>muscle tissue. The bioaccumulation pattern for Pb was determined as gills>liver> kidney>stomach>muscle tissue. Maximum mean concentrations of Pb 6.87±2.25mg g-1 dry weight belonged to gills. Bioaccumulation pattern for Cd in the different organs studied in A. persicus was kidney>liver>gills>stomach> muscle tissue. Maximum mean concentration of 5.1±0.97mg g-1 dry weight belonged to kidneys and the minimum mean concentration of 0.05±0.007mg g-1 dry weight belonged to muscle tissue. Concentration of the metals in the muscles samples were below the most guidelines for human consumption.Concentrations for heavy metals were lower than the guidelines in some organs and were higher than that in the other organs studied. The observed concentrations do not pose health problems as these organs are not used for human consumption.

Carp is one of the most widely cultivated warm water fish, which has been introduced into many countries. It is essential for the manager of a carp farm to know the production costs and their evolution, showing the main inputs on which the cost reduction is worth effort. In Iran, carp farming is mainly based on common carp, silver carp, grass carp, and bighead carp, which were often reared in poly culture. Carp farming production reached a peak in 2006 with production of more than 77,000 tones. The characteristics of the carp farming industry in the main fish farming provinces, (overall more than 90% of total carp production) are considerably different. In years 1996 and 2001, a study of yield production, factor costs and profitability of farmed carp was carried out to help clarify carp production costs and their difference between the provinces. 153 farms in 1996 and 101 farms in 2001, overall, a total of 254 farms from the main carp farming provinces, including; Guilan, Mazandaran and Khuzestan were randomly selected, classified and studied. Results showed that the various producer provinces have different cost structures. Overall, feed and fertilizer with the highest level of variation accounted for 45% of total costs in 1996, declined to 23% in 2001. However, on average, cost of seed and labor increased from 7% and 10% to 23% and 17% of total costs over the 1996 and 2001, respectively. On average, benefit-cost ratio and the rate of farm income were closely related to location suggesting that farmers practiced more efficiently and have better conditions in Guilan in 1996, resulting in higher farm income per ha and per kg, changing to better conditions and more efficient by Mazandaran province in 2001. Overall, in the three main provinces, rate of farm income from an average of 20% in 1996, declined to 12% in 2001.

In the present study, changes in benthic communities due to seasonal changes in the water of the southern Caspian Basin were investigated. Sampling was conducted monthly, from March 2006 to March 2007, at six selected stations in Tajan River mouth located on south eastern Caspian Sea. Also secondary benthic production consumable for fish and other biota inhabiting the mouth and adjacent areas were estimated. Forcing and limiting factors were also discussed. Benthic communities comprised 9 taxa, of which Ballanus sp., Chironomus plumosus and Cerastoderma lamarki were the main contributors to both overall biomass and secondary production. Annual secondary production varied from 3.8g AFDWm-2 y-1, in the upper part of the mouth, to 78.06g AFDWm-2 y-1 in the center of the estuary area. Multivariate correlations between environmental variables and the macro benthic biomass highlighted the role of the water level, temperature, organic carbon content and dissolved oxygen which resulted in separation of communities in the estuary. Composition, biomass and secondary annual production of macro benthic communities were dramatically affected by changes in water residence time and summer drought crises. The isolation of this habitat limits the recovery of other benthic fauna during drought periods. Only populations of two taxa, Balanus sp. (Cirripeda) and C. plumosus (Diptera) seemed to be able to recover quickly after the drought crises, which, in turn, could compromise the overall secondary production, which may have negative effects on fish and other superior organism’s survival. During summer water renewal, when agricultural activities are intense, nutrient inputs should be regulated in this estuary to reduce the risk of benthic mass mortality and to ensure a sustainable ecosystem.

Tinca tinca is originally from the Near East and West-Siberia and nowadays is spread all over the world (Lukowicz & Proske, 1979). Previous reports showed that they abundantly present in therivers flowing to the Black Sea and various lakes as well as in rivers in Central Anatolia (Kuru, 1999). It has no economical importance due to its slow growth rate and tasteless meat.There are many publications on the growth (e.g, Cerny, 1968; Lukowicz & Proske, 1979; Alaş, 1998; Altındağ et al., 1998; Altındağ et al., 2002; Balık et al., 2004; Ergönül & Altındağ, 2005; Erol et al., 2006; Balık et al., 2009), the biology (e.g., Göktaş, 1987; Q’Maoileidigh & Bracken, 1989; Vetlugina, 1992; Neophiotu, 1993; Yılmaz, 1997) and the bio-ecology and feeding (e.g., Bircan, 1988; Balık et al., 1997; Şanlı, 1998) of T. tinca…