Feeding and reproductive biology of Saurida undosquamis (Richardson, 1848) from Parangipettai coast, Southeast coast of India.
The feeding biology, spawning season, size at first maturity, sex ratio and fecundity of the commercially important lizardfish (Saurida undosquamis) were studied in Parangipettai waters of the southeast coast of India. Fishes formed the predominant food item. Diversity of the prey items showed maximum value (H'log 2-3.61 +/- 0.11) during the postmonsoon season and minimum during the monsoon season (2.89 +/- 0.17). The richness (1-lambda') also showed a similar trend and varied from 0.81 +/- 0.13 (monsoon) to 0.91 +/- 0.01 (postmonsoon). The size at first maturity (50% incidence of mature fish) was 195 mm. But when the size at first maturity was calculated by adjusting the proportion of maturity percentages, the maturity size was found to be 140 mm. This method is advantageous from the point of view of fisheries management as this species can be exploited above 140 mm rather than above 195 mm. The gastrosomatic index was found maximum during postmonsoon and minimum during the monsoon season showing the inverse relationship between feeding and spawning. This species was found to spawn from August to January with a peak in November. The fecundity ranged from 19, 856 in a fish measuring from 20.1 cm in length (97 g) to 79,282 in a fish of 29 cm (290 g). The overall sex ratio (1:1.19) was found to deviate significantly from the expected 1:1 ratio. (chi2 = 19.1, p < 0.005). Month- wise, it conformed to the expected 1:1 ratio during most of the months except January, June, September, November and December. Higher gonado-somatic index values observed during October-December suggested spawning activity during this period. This species is found to a total spawner in the Parangipettai waters.
Age, growth and reproduction of the lizard fish Saurida undosquamis from the Gulf of Suez, Red Sea, Egypt
The lizard fish Saurida undosquamis represents one of the most commercial fish in the Gulf of Suez. The growth and reproductive biology of the species were studied. The age was determined from otolith readings of the collected specimens from the Attaka Harbor through the period from September 2011 to April 2012. The results show that the life span of the sampled fish was seven years. The estimated von Bertalanffy growth equation was Lt=51.252 (1-e -0.131(t+1.45) ), the calculated lengthweight relationship was W= 0.004 L 3.107 . Seasonally distribution of gonado-somatic index (GSI) values showed that the main peak of GSI was in spring. The results of gonad development stages show that, Saurida undosquamis is a synchronous spawner. The size at which 50% of fishes are mature was 15.0 cm for males and 15.5 cm for females, which indicates that all individuals over one year of age were sexually mature. The results indicated that juvenile individuals are one of the targets of the fishery and the protection of the juveniles is probably the key factor for the sustainability of the resources.
Variations in plaice fecundity in the clyde area
The fecundity of Clyde plaice, which has been studied from 1956 to 1961, has not been found to change as the breeding season approaches. However, there was a marked fecundity change from about 137 thousand eggs to around 161 thousand after 1957. The fecundity of all age groups increased and this appears to be associated with the fishing intensity and so the population density. Heavy fishing leads to fewer fish with the same food supply which in turn allows higher fecundity. The changes in fecundity therefore seem to be part of a density dependent population regulating mechanism.