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Abstract
CHAPTER FIVE
SUMMERY
Striped mullet Mullus surmulatus is one of the demersal fish species belonging to the family Mullidae that is distributed along the eastern Atlantic from the English Channel to the northern part of West Africa and the Mediterranean Sea. In the countries of the Mediterranean Sea, the striped mullet is a highly exploited fish.
The aim of this study is to give information about the different biological parameters of the fish under study such as Biometric characters which include Morphometeric and Meristic characters, and also the length- weight relationships, Age determination and the relation between age and growth, Histology of gonads during the spawning season and the explanation of some differences between the male and the female in this aspect, Fecundity of the female and its relation with the length, weight and age and finally the Food and feeding habits of this species.
For the previous purposes the present study was carried out on Mullus surmulatus at Alexandria during the period from June 2006 to July 2007 on both male and female. The results of this study could be summarized as follows:
For the biometric studies, about 700 individuals of Mullus surmulatus ranging in total length between 10.0 and 29.0 centimeters were examined. For each fish, fourteen measurements of the different body parts of the fish were measured to the nearest centimeter, the morphometeric index of each measurement was calculated for every fish group as a numerical ratio between this measurement and the suitable reference which is the total fish length or the head length. By applying the regression on the morphometeric measurements of Mullus surmulatus, distinctly straight lines were obtained, which indicate the isometric growth of the fish. The fork and standard lengths are directly proportional to the total length, and this points out to the faster growth of the fish. Also the body depth and head length increase with total length but with a narrow range.
Seven meristic characters were studied; the number of dorsal, pectoral, pelvic and anal fin rays, vertebrae, gill rakers on the first gill arch on the left side and scales on the lateral line. And the results were as follows:
Vertebrae = 23, Gill rakers = 29, Scales = 34, Dorsal fin rays = 8-5, Pectoral fin rays = 14, Anal fin rays = 7 and pelvic fin rays = 6.
When the length-weight relationship is represented graphically, a curvilinear shape can be obtained, the following are the equations that explain the L.–W. relationship for M. surmulatus :
For males : W = 0.0052 X L3.259
For females : W = 0.0063 X L3.198
For combined sexes : W = 0.0061 X L3.211
where as it gives a straight line when expressed in a logarithmic form :
Males : Log W = -2.28473 + 3.259 Log L
Females : Log W = -2.19876 + 3.198 Log L
Combined sexes : Log W = -2.2145 + 3.211 Log L
These equations show that the weight of M. surmulatus increases in proportion to the cube of its body length. This proves that it is an ideal fish with isometric growth.
Condition factors of the fish were determined, the mean values of the two types of condition factors for length interval from 10.0 to 29.0 cm of Mullus surmulatus for each of male, female and combined sexes were:
For males Kc = 0.519, Kn = 0.998, for females K c= 0.633 while kn= 1.0 and for combined sexes Kc= 0.61 and Kn = 0.999. These results show that both males and females behave similarly with regards to their condition factors.