Iranian Journal of Fisheries Sciences
Year:2007 | Volume:6 | Issue:2|Papers Count:15

The impact of two principal parasitic digenetic trematodes, Meiogymnophallus minutus and Himasthla spp., on the growth (weight and length) of the cockle, Cerastoderma edule, in Arcachon Bay (France) was studied. The experiment was conducted in the land-based mesocosms. The velocity of infestation with both trematodes was far more rapid during summer in the cockles already parasitized with these trematodes (0.35 to 0.45 metacercariae day-1) than those of healthy ones (approximately 0.01 metacercariae day-1). The parasitism had also an effect on the growth rates of cockles. During 190 days of the experiment, the daily growth speed varied from 0.001mm.da/ to 0.021mm.day-1. On average, the growth was slightly more important in healthy cockles after the start of experiments (0.014mm.day-1) than those initially infested cockles (0.011 mm.day-1). The experiment also showed that infestation of hosts with trematodes could perhaps disturb their immunity system, as the intensification with trematode parasites had been favored by already infested cockles.

The effectiveness of two kinds of dopamine antagonist (DA), metoclopramide (Met) and domperidone (Dom) combined with the gonadotropin releasing hormone analogue (D-Ala6, Des Gly10 ethylamide) GnRHa was assayed on the ovulation success, latency period, ovulation index (OI) and fertilization success of kutum, Rutilus frisii kutum (Kamenskii, 1901). Brood fish were injected intra-peritoneally as follows: 2 mg/kg b.w. of carp pituitary extract (CPE) as a control, 5 g+ 2.5mg, 1mg+ 5mg and 2mg+ 10mg/kg b.w. of GnRHa + Met or Dom in a single injection.Based on the ovulation and fertilization success, no significant differences between similar doses of Dom and Met when combined with similar doses of GnRHa were found (P>0.05). However, in some groups, the OI and latency period were greater when Dom was used as a DA instead of Met (P<0.05). In general, the results of this study showed that the potency of Dom was nearly same as Met when combined with GnRHa and used as a DA in kutum. It is strongly recommended to repeat the experiment under different conditions to find out definite conclusion.

The salinity tolerance and hydromineral regulation capabilities of juvenile great sturgeon, Huso huso, of different age and size groups (1: 35 days, BW: 0.60±0.02g &TL; 4.80±0.13clp; II: 35 days, BW: 2.23±0.20 g & TL: 7.19±0.17cm; III: 35 days, BW: 9.91±0.23g& TL: 11.86±0.24cm; IV: 50 days, BW: 3.97±0.25 g & TL: 9.34±0.18cm; V:50 days, BW:22.27±1.9g & TL: 17.25±0.35cm; VI: 65 days, BW: 6.3±0.67g& TL: 11.37cm ; n=90 for each group) in freshwater (FW:0.5% 0), estuary water (EW:9.5 %0)'and the Caspian Sea water (CsW:12.5% 0) were investigated. The fishes are directly transferred from FW to EW and CsW. The possible repercussions of osmoregulatory processes on some indicators of classical were examined at the end of 168 hours fish acclimation. Mortality was observed (higher than 50% after 72 hours) only in 1stgroup in EW and CsW. Some haematological parameters, namely haematocrit (Hct), red and white blood cells count (RBC, WBC), mean cell volume (MCV), hemoglobin concentration (Hb), mean cell hemoglobin concentration (MCHC), the amount of haemoglobin per erythrocyte (MCH), levels of cortisol, osmolarity and ion concentration (Na+, K+, .16 S.M. Farabi et ai., Ca+2 and Mg+2) in the plasma were determined. The functional levels of the mechanism of osmotic and ionic homeostasis were similar in different groups (II to VI) but differed in experimental media (P<0.05). Significant differences were observed between the levels of serum Na+ concentration in different groups in EW and CsW media (p<0.05). Serum Na+ and Ca+2 concentrations were higher than those of FW and EW media, but lower than in CsW media. The Hct, MCV and MCH decreased with increase in fish age, and decreased from FW media to CsW media with increasing salinity; RBC, WBC and MCHC did not change. The trend of increasing levels of cortisol were observed at higher salinity in each group (P<0.05). However, Hct, MCV, MCHC, cortisol, osmolarity and ion concentration values did not return to initial values (P<0.05), showing that osmoregulatory processes caused major physiological changes in this species.

A sex steroid-binding protein (SBP) that binds to 17 b-estradiol with high affinity and moderate capacity was identified in the plasma of female and juvenile of kutum (Rutilus frisii kutum) sampled during the early stage of gonadal maturation in October and prior to spawning in March.Mean maximum specific binding (Bmax)and equilibrium dissociation constant (Kd) of the fish were as follows: In early stage of gonadal development (October), Bmax= 5800±970 fmol E2/m gprotein, Kd 4.1±0.6nM, and prior to spawning (March) Bmax= 4000±895 fmol E2/mgprotein, Kd 2.9±0.3nM. In juvenile sampled in October Bmax= 1600±130 fmol E2/mg protein, Kd 2.1±0.2n M and in March samples B max= 3500±780 fmol E2/mg protein, Kd2.2±0.2nM. Plasma estradiol binding characteristics of the adult samples in October and March differed from the juvenile samples in having both Bmax and Kd significantly higher than juveniles. Plasma SBP levels displayed a moderate correlation with GSI (r2= 0.52) and CF (r2= 0.51) and a weak correlation with HSI (r2 = 0.28). Affinity was moderately correlated with CF (r2 = 0.68) and HIS (r2 = 0.50). A strong correlation was obtained between Bmax and Kd, high Bmax values coincided with high Kd values and vice versa.

The experiments with Beroe ovata showed that this ctenophore can survive and reproduce in the Caspian Sea water, though at far lower rate than in the Black Sea; larval growth in the Caspian Sea water was also slower and mortality higher. Maximum fecundity of 2210 and 240 eggs recorded in laboratories of Turkey and Iran, respectively. About 34 to 100% of eggs in the Caspian Sea water could not develop and hatch. Larvae were at different stages of development, usually with size between 1.2 to 2mm. The highest number of eggs and larvae were obtained in tanks where Beroe individuals were together with Mnemiopsis leidyi. The poor reproduction of B. ovata in the Caspian Sea water could be due to both the acclimation stress to low salinity and possible damage of individuals during the transportation.

The efficiency of different types of traps for catching of the Caspian Sea crayfish, Astacus leptodactylus eichwaldi, was investigated from Mar. 2002 to Feb. 2003. Totally 56 traps of four most commonly used types, "Rectangular trap", "Round trap", "Opera house trap" in two colors of "black" and "blue", and "Fathoms plus" only in black were installed in depths of 35, 45, 55 and 65 meters along two transects in Anzali coastal area.The results revealed no significant differences (P≥0.05) in the average length; weight and sex ratio among the crayfish in different months and applied traps.However, significant differences (P<0.05) in CPUE of different traps in various months of the study year were observed. Mean annual of CPUE in Opera house traps "blue" was the greatest (5.09±0.29) and the lowest was found in "Fathoms plus" traps (0.28±0.05). In general; all blue color traps performed better catch thanthe black ones.

Apoptosis is a programmed cell death that has been attributed to the action of stress hormones, such as cortisol. We investigated the in vitro effect of cortisol in goldfish (Carassius auratus) mature (GSI: 2.75-4.65) or immature (GSI: 1.94-2.4) testes. Testes were taken out and transferred into culture medium (M 199), cut into 20 mm thick slices and supplemented with fetal bovine serum (FBS), added different doses of cortisol (0, 50, 100, 200, 400, 750 and 800 ng/ml) and incubated for 24h, 48h or 72h at 18°C. Samples were rinsed and homogenized with phosphate buffered saline (PBS) after incubation period. Duplicates or triplicates processed for caspase-3 activity. The results showed a significant increase in caspase-3 activity in immature testes after 72h treatment with 750ng/ml of cortisol (P<0.05), and also at 400ng/ml (P<0.05). In contrast, no significant differences were observed between non-treated and cortisol-treated samples from mature goldfish testes. In this study we have demonstrated, for the first time that the stress hormone cortisol induces apoptosis in the goldfish testis in a stage-specific manner (immature testis).

Ensiling as one of the best methods for utilization of tuna wastes was investigated. docosahexaenoic acid [DHA C22:6(n-3)]- rich products were obtained from the wastes (viscera and dark meat) of four tuna species, namely longtail, skipjack, yellowfin and kawakawa by a procedure involving ensiling in organic acids followed by neutralization. Identification of fatty acids in the samples was performed by comparison with chromatograms of fatty acids standard. Total lipid content of silages varied from 10.41% in skipjack dark meat silage to 22.01% in kawakawa viscera silage, but all lipids contained high percentages of DHA and EPA [eicosapanteoneic acid C20:5(n-3)]. The highest DHA ratio (15% of total lipids) was found in the lipid of skipjack viscera silage and the highest ratio of EPA (11% of total lipids) belonged to the lipids of kawakawa dark meat silage.ANOVA test results indicated that DHA ratio was significantly high before silage preparation and linolenic acid [C18:3(n-3)] content significantly differed between the species (P<0.05).

Some reproduction characteristics of keeled mullet, Liza klunzingeri, were studied during Apr. 2003 to Feb. 2004 in Khuzestan waters of the Persian Gulf.A total of 836 samples were monthly collected from two fish landings of Bahrekan and Hendijan; 727 specimens were studied from point of sex determination, and 60 specimens were studied from the fecundity point of view. This species was found to have more abundance in autumn (esp. Oct-Nov). The samples composed of 89 (12.2%) male, 467(64.2%) female and 171 (23.6%) immature; the sex ratio was M:F = 1:5. The advanced stages of maturity (4th& 5th) were found in October onward. The highest Gonadosomatic Index was in December and the lowest was in June. The maximum absolute and relative fecundities were 183040 and 2232, respectively; the minimum absolute and relative fecundities were 44700 and 582, respectively. The minimum and maximum egg diameter was 0.04mm (stage 2nd) and 0.75mm (stage 6th).