مجله علوم و فنون دریایی
سال نهم شماره 2 (تابستان 1389)

There have been relatively very few taxonomic studies on the Brachyura of the Persian Gulf region, despite the recent ecological focus on the area due to its economic importance. The present descriptive study is based on the brachyuran larvae (Zoea I) of six species of family Leucosiidae: Myra fugas, Philyra platychira, Philyra globus, Philyra sp1, Philyra syndactya, Ebalia sp1. Plankton samples were collected monthly from coastal waters of Khuzestan from May 2007 to April 2008. The larval stages are described in detail and the variations between morphological characteristics of larvae are presented in tabular form. Dominant species was Philyra platychira with maximum abundance in June 2007.

Salmo trutta caspius is a euryhaline fish that tolerate salinity fluctuations during the maturation process with a number of morphological and functional adaptation. There is little information about kidney of this native Caspian species that play an important role in ion balance in body fluids is information exists. In the present study ontogeny (development process) of renal system (kidney and urinary bags) in terms of structure and function in osmotic regulation from first day post hatching to 27 days through histology and immunohistochemistry were studied. Results showed that on the first day post hatching, proneprosic kidney was located along the body and digestive tract. Until the sixth day, Poximal tubules showed low complexity but in next days they showed differentiation and increased in number and complexity. mesonephric tubules appeared with dark cell mass on sixth day. Glomeruli was seen on days 12 after hatching and was characterized by mesonephric and blood cells and Bowman capsule. Between days 16 to 22 number of mesonephric tubules was increased, so that blood tissue between them decreased and all the the renal tissue was embedded by tubules. After that formation of mesonephric kidney with decreased blood tissue and Pronephric tubules was observed. Imunolocalization of Na+ / K+ ATPase in one-day larvae was seen strongly in many parts, means that lots of this enzyme is available in basal membrane. By growing larvae, immunofluorescence intensity in different parts of the kidney showed significant changes. It could be concluded¬ until formation of Mesonephric kidney, the main role in osmotic regulation is played by Pronephric tubules but later this role is transferred to mesonephric tubules.

Salting is one of the oldest fish preservation methods. In recent years, salting procedures are changed, not only to preserve the fish but also to improve its aroma and flavor. In this study effects of two temperatures (4 and 10 C) in two times (6 and 12 hours) on chemical composition and sensory quality of light dry salting was assayed. Experiments were carried out in completely randomized design as a factorial with tree replicates. The salt concentration in light dry salting was 10%. The salt changed chemical composition and sensory quality in muscles of fish. By increase in salting time from 6 to 12 hours, moisture and protein decreased to 3.13% and 1.2% in 4 C and 3.57% and 1.5% in 10 C, respectively. The light salting of fillets increased ash and muscle salt content and induced pH, fat and sensory quality changes. The results showed that use of light dry salting in rainbow trout fillets in lower times produce a good quality product.

This experiment was conducted to examine the effects of dietary nucleotides on growth, and intestinal morphology of rainbow trout with mean initial weight of approximately 11.35 ± 0.01 g. Five diets with 0, 0.5, 1, 1.5 or 2 g of nucleotides (NT) Kg-1 diet were fed to rainbow trout for 8 weeks. Forty fish were kept in each of the triplicate tanks designed for every treatment group. Fish fed diets with 2 g and 1.5 g NT Kg-1 for 8 weeks had highest final weight and SGR and lowest in fish fed the NT-free control diet. After 8 weeks of feeding trial, there was a significant (P<0.05) decrease in FCR between the control and the groups fed diets with 1 g, 1.5 g and 2 g NT Kg-1. The highest length of intestine epithelium cells was observed in fish fed diets with 0.2 g NT Kg-1. The results suggest that dietary nucleotides exerted positive effects on growth indices and intestine morphology in rainbow trout.

The purpose of this study was to investigate weight–length relationship of Caspian Lamprey, Caspiomyzon wagneri, in two Shirud and Talar Rivers. Totally, 242 fish specimens were collected using hand and a circle cast-net during their spring migration (from 22 March to 9 May, 2006). The most length frequency in both sexes was 367–369 mm. Weight–length relationship revealed a positive, high and significant correlation in the Shirud River population (male: r = 0.89 and p = 0.00; female: r = 0.86 and p = 0.00) and Talar River (male: r = 0.93 and p = 0.00; female: r = 0.74 and p = 0.00). Growth pattern was negative allometric between sexes and rivers. The coefficient of condition in females was higher in the rivers, but there was no significant difference between populations (p ≥ 0.05). The sex ratio (male to female) was 1.1 to 1 and 1 to 1.1 in the Shirud and Talar Rivers, respectively. Investigation of lamprey gut in both rivers showed that in most of them gut was empty of food and in some of guts observed parasite Corynosoma sp. from Acanthocephal groups was observed. The results this study showed that growth parameters are similar in two rivers.

The three-dimensional variability of refractive index in the Persian Gulf water was investigated. In this study a three-dimesional hydrodynamic model (COHERENCE) was employed in a fully prognostic mode to derive refractive index in the Persian Gulf, an evaporation–driven inverse estuary that is governed by the import surface water from the adjacent ocean and the export of saline bottom gulf water through the Strait of Hormoz. The results showed that the minimum and maximum refractive index occurred in the bottom waters in January and July, respectively. Generally refractive index in the bottom waters was greater than that of the surface waters except in November and January. In addition, refractive index in the southern parts was greater than that in the northern regions of the Persian Gulf. Finding of the show a very good agreement with real observation.