Iranian Journal of Fisheries Sciences
Volume:7 Issue: 2, Jul 2008

Surface sediments contamination to heavy metals was evaluated in eight creeks of Mahshahr coastal waters (north-west of the Persian Gulf) from October. 2005 to November 2006. Sediments were collected seasonally by Peterson grab and the concentrations of heavy metals were measured using voltammetry and polarography methods. The range and the mean concentrations obtained in mg/kg were 15.03-35.16 (27.01) for Cu, 65.57-171.41 (102.67) for Ni, 4.63-20.06 (13.22) for Co, 0.093-0.78 (0.22) for Hg, 65.07-379 (113.70) for Zn, 0.27-1.00 (0.56) for Cd and 7.09-29.72 (14.66) for Pb. The background values for different heavy metals were calculated and the contamination factor for each metal and the degree of contamination for each creek were determined as well. Measured concentrations were compared with international standards. According to the contamination factor (Cf), the concentration of some elements such as Hg, Zn, and Ni were at risk level; according to the degree of contamination (Cd), all of the studied creeks could be classified as moderately polluted except for Ghannam that showed a considerable degree of contamination.

: The effect of feed supplemented with L-carnitine at four levels of 0, 300, 600 and 900mg kg-1 on growth performance and body composition of beluga, H. huso, juveniles was evaluated in two separate trials. In the first trial, 180 juveniles (525±9g) were fed with the test diet for a period of 71 days, and the trial extended to another 126 days in the second phase by randomly selecting 120 juveniles (870.7±32g) and rearing them with similar diets. All trials, in triplicates, were conducted in circular fiberglass tanks (200cm diameter, 40cm height). The fish were fed 4 times daily to apparent satiation. In the first phase, L-carnitine did not significantly affect mean final weight, feed conversion ratio (FCR) or specific growth rate (SGR) of the fish, however, the fish receiving 900mg kg-1 L-carnitine showed better growth increment, SGR and feed efficiency (FE) than those in control group (P≥0.05); neither did it significantly affect protein, lipid, moisture or ash as well as hepatosomatic index (HSI) (P≥0.05). The protein efficiency ratio (PER) was significantly affected by L-carnitine supplemented diet, particularly at 900mg kg-1 (P≤0.05). In the second phase, fish fed L-carnitine-supplemented diets produced significantly higher W2, SGR and PER than the control group (P≤0.05), but HSI decreased significantly (P≤0.05). At the end of the trial, the whole body composition of fish did not differ significantly among experimental treatments, but slightly reduced lipid content were observed at 600 and 900mg kg-1 L-carnitine (P≥0.05). The results of this study indicated that supplementation of diets with 300-600mg carnitine kg-1 improved growth rate, feed utilization and stimulated protein-sparing effect in this species.

Growth, feed conversion ratio and fillet composition of rainbow trout (initial weight of 9.99±0.109) were investigated in a 6×2 factorial design experiment employing two levels of digestible energy (DE) (2900 and 3500kcal.kg-1) and six feeding rates (1.0%, 2.0%, 3.0%, 4.0%, 5.0% of the body weight (BW) day-1 and to satiation) for 60 days. Specific growth rate (SGR) was highest at 5.0% ration in both levels of digestible energy and decreased in the satiation ration. Regardless of feeding rate, rainbow trout grew more by 35% in DE 3500 kcal kg-1. There was a significant (P<0.05) interactive effect of feeding rates and DE on weight gain and feed conversion ratio (FCR). The highest FCR was found in fish fed to satiation (19-21%), while the lowest FCRs, were found in 4%, 3% rations in DE levels of 2900 and 3500kcal kg-1, respectively. There was a significant increase in protein and fat levels and decrease in moisture content of fish fillet (P<0.05) as feeding rate and DE increased (P<0.05). Condition factor increased when feeding rate and DE increased (14–15%). Feeding rate and DE level proved to be the main differentiating factors in growth, FCR and fillet composition parameters. Values of SGR and FCR plotted against feeding rates allowed the optimum and maximum feeding levels to be determined, which were found to be at 4% and 3%kcal day-1 in DE levels of 2900 and 3500kcal kg-1, respectively, for the rainbow trout of l0g average weight.

Carapace length frequency data of green tiger prawn, Penaeus semisulcatus, were monthly collected from 50 stations along the coastal waters of Bushehr, Persian Gulf, during January 2003 to March 2004. FiSAT program was used to analyse a total of 535 shrimps including 292 females and 243 males, for the relationships of total length, weigth and carapace length. The L and K for males were estimated at 38mm CL and 1.6 year-1 and for the females were 50.40mm CL and 2.20 year-1, respectively. Maximum age (Tmax) were 20 months for the males and 15 months for the females. The growth of the shrimp was found to be rapid during summer and autumn and negligible during winter and spring.

A 60-days feeding trail was conducted to evaluate the effects of dietary digestible energy levels (DE) on kutum, Rutilus frisii kutum. Four isonitrogenous (35% protein) diets with digestible energy levels of 2500, 2600, 2700 and 2800kcal kg-1 were tested. Two hundred and forty advanced fry (2±0.4g) were randomly distributed in 12 fiberglass tanks of 400L capacity. Nutritional responses in terms of WG, FCR and PER as well as survival rate (SR) significantly improved (P<0.05) with increase in DE level from 2500 to 2800kcal kg-1 diet, but no difference between 2600 and 2700kcal kg-1 diet was found. Body crude protein and fat significant were increased (P<0.05) when the dietary energy was raised up from 2500 to 2600kcal DE kg-1 diet, but a further increase on energy did not improve the fish crude protein and fat content.

The effect of aqueous solution of citric acid (CA) on the lipid stability of the European catfish (Silurus glanis) fillets during frozen storage (up to 6 months) was investigated. Rancidity development was measured by several biochemical indices (free fatty acids, peroxides and TBA) and complemented by the measurement of expressible moisture and sensory evaluation (flesh odor, consistency and flesh appearance). The CA treatment led to some lower free fatty acids (6.43% oleic acid in total lipid at month 6), peroxides (7.98meq oxygen/kg lipids, at month 6) and secondary compounds formation (2.16mg malondialdehyde/kg fish sample). Lower peroxide, thiobarbituric acid-reactive substance (TBA), free fatty acids (during 0, 3 and 6 months frozen storage), and expressible moisture (month 6) values were obtained from CA-treated fish fillets than the untreated (blank control) ones (P<0.05).

Genetic relationships among 96 specimens of ship sturgeon, Acipenser nudiventris, collected from six locations along the Iranian coastline as well as 8 specimens from northern population (Ural River) were analysed by the restricted maximum likelihood method, as well as two distance analysis method (Nei’s and Cavalli-Sforza’s distance) of gene frequencies. We have used four SSR makers that produced three polymorphic and two monomorphic loci. Overall results showed that Iranian coastline samples form a monophyletic group (clade) which was different from the northern (Ural) samples. Iranian coastline samples are divided into two groups (clades): Anzali-Kiashahr clade and Sefidrud-Babolsar-Noushahr-Gorgan clade. Bootstrapping test showed monophyleticity of Sefidrud, Babolsar, Noushahr, Gorgan with high (Bootstrap support=93) and Anzali-Kiashahr with middle (Bootstrap support=65) confirmation. Topology of reconstructed trees was in correspondence with geographical distributions of samples.

A digestibility trial was conducted to examine the effect of feeding rate on dry matter, gross energy, crude protein and phosphorus digestibility in Atlantic salmon (Salmo salar). Duplicate groups of fish were fed 0.25, 0.5, 0.75, 1.0, 1.25 and 1.9% BW/day. The faeces were collected by Guelph-type collectors for five successive days. Dry matter, protein and phosphorus digestibilities were all significantly (P<0.05) affected by feeding rate. Dry matter digestibility was significantly lower in fish fed 0.25% BW day in comparison with fish fed 0.5, 0.75 and 1% BW day. Protein digestibility was significantly lower in fish fed 0.25% BW/day in comparison with 1.25% BW day. Phosphorus digestibility was significantly lower in fish fed 0.25% BW/day in comparison with all other treatments except for 1% BW day. There were no significant differences for energy digestibility between fish fed with different amount of feed. The main effect was reduced digestibility at the lowest level of intake with no obvious relationship between feeding rate and digestibility above this amount. This was explained by a relatively higher loss of endogenous faecal nitrogen and phosphorus at sub-maintenance feeding.

Length composition data of narrow-barred Spanish mackerel, Scomberomorus commerson (Lacepède 1800), landed between April 2002 to March 2004, were monthly used to estimate the growth, mortality and exploitation parameters of the stock. Maximum fork length and weight were 170 cm and 38 kg, respectively. Nonlinear least square fitting provided a complete set of von Bertalanffy growth estimates: L∞= 178 cm (FL); K=0.28 and t0= -0.36 years. The estimated value of total mortality based on length converted catch curve using these growth parameters is Z=0.95 year-1. Natural mortality based on growth parameters and mean environmental temperature (T=26.5ºC) is M=0.36 year-1. Furthermore, the annual instantaneous fishing mortality rate of 0.59 year-1 was by far in excess of the precautionary target (Fopt=0.18 year-1) and limit (Flimit=0.24 year-1) biological reference points, indicating that the resource is heavily over-exploited and the management of this species should be implanted rapidly if they are to remain sustainable.