The Systematics of Indo-Pacific Saur1va and Trachinocephalus (Pisces: Synodontidae) and the Biology of Four Local Species

Abstract

Lizardfish species of the genera Saurida Cuvier and Valenciennes and Traohinoeephalus Gill 1862 in the Indo- Pacific are morphologically cryptic and widely distributed. Their habitats range from shallow water to deeper waters, sand/muddy bottoms or reefs. Many morphological features of lizardfish are variable and often of limited value in establishing taxonomic relationships. Synonymies and especially misidentifications are prevalent. An exploratory electrophoretic analysis confirmed intra-specific variation but also revealed specific differences which reflected species affinities. Accordingly the diagnosis of Indo-Pacific Saurida is revised and eleven species - S. argentea, S. australis, S. elongata, S. filamentosa, S. flamma, S. gracilis, S. isarankurai, S. longimanus, S. nebulosa, S. tumbil and S. undosquamis - are described. 5. australis is removed from the synonymy of S. undosquamis and interrelationships between members of the genus are described. S. wanieso and S. micropectoralis both described by Shindo and Yamada (1972) are synonymized under S. filamentosa and S. argentea respectively. S. wanieso is considered as a geographical race of S. filamentosa whereas S. micropectoralis is, by priority, a junior synonym of S. argentea. The biology of lizardfish were studied from collections taken within and without Moreton Bay between August 1979 and December 1981. The analysis of stomach items and morphological adaptations revealed that the food and feeding strategies of lizardfish consist of adaptability to a wide range of food items, food sizes and environmental conditions instead of specialization to few food items. The most important component of stomach items (by frequency of occurrence) were fish in over 85% of stomachs analysed (i.e. those with food). The other two major components were Crustacea and Cephalopods in about 5-16% and about 7% respectively. Stomach content analysis indicated that lizardfish fed during both day and night. Mouth and body structures are well suited to their hunting techniques and carnivorous mode of feeding. Lizardfish reproduction within and without Moreton Bay is described with emphasis on the development of the gonads. Four types of eggs based on size and yolk content are described. Eight and six stages of identifiable gonads based on a) types and quantities of ova present and b) texture and macroscopic appearance are described for the ovaries and testes respectively. The species exhibit size polymorphism - the females predominate in sizes greater than male S.L^q whereas the males predominate in sizes about the male S.L.^q and below. The reproductive strategy involves an extended spawning season, early maturation, high fecundity coupled with serial spawning. The ages of S. tumbil, S. undosquamis and T. myops on the one hand and S. filamentosa on the other were determined by the scale and vertebrae methods respectively and were supplemented by the length frequency method. The observed maximum ages in the species were 5, 4, 12 and 3 for S. undosquamis, S. tumbil, S filamentosa and T. myops respectively. Lizardfish growth is asymptotic and alloraetric and was described in terms of Von Bertalanffy and other growth parameters. The overall growth strategy apparently involves a number of features - very rapid linear growth, early maturation, annual and allometric growth. The four lizardfish species were parasitized by cestodes, hemiurid trematodes, nematodes, isopods and acanthocephalans. Negative binomial distribution (truncated and non-truncated) analyses in comparison with actual frequency distribution of the most common parasite in Moreton Bay, Callitetrarhynohus gracilis (Rudolphi) 1819, suggested that ’heavily’ infected fish were missing from the samples.