Pakistan J. Zool., vol. 40(4), pp. 249-253, 2008. Effect of Different Preservatives on the Biomass of some Selected Marine Fauna NAUREEN AZIZ QURESHI*, NOOR US SAHER, RAOOF MUHAMMAD NIAZI AND MUHAMMAD ASIF GONDAL Centre of Excellence in Marine Biology, University of Karachi, Karachi (NAQ, NUS), Government City College, Nazimabad, Karachi (RMN) and Lasbela University of Agriculture, Water and Marine Sciences, Uthal, Balochistan (MAG) naureenaziz@yahoo.com, saherj2002@yahoo.com, asifmariner@yahoo.com, raoofmniazi@yahoo.com Abstract.- The effect of 70 % ethyl alcohol and formalin (1 % and 10% ) was studied on the biomass of crabs, shrimp and fish. Significant weight loss was observed in crabs (4.6 to 33.2%) in shrimps (2.5 to 41.4%) and in fish (26.5 to 59.5%) when preserved in 70% alcohol for ten weeks. The wet and dry weights of crabs also decreased significantly with time when preserved in ethyl alcohol and formalin. There was no significant difference in the weight of shrimps, whereas the fish weight loss was significantly different for both the preservatives. There was no significant difference in the wet and dry biomass of fish. Key words: Preservative, biomass, crabs, shrimps, fishes, formalin, ethyl alcohol. INTRODUCTION Various chemicals and freezing are used to preserve animal specimens for teaching and demonstration purposes. Preserved animals are also kept for longer periods in museums as type specimens. Field samples are also often stored for subsequent biomass estimation. Formalin (1-10%) and ethanol (70%) are the most commonly used preservatives of aquatic and terrestrial vertebrate and invertebrate fauna (AIHA, 1989; Gaston et al., 1996). The fixatives (preservative) primarily arrest the physical and chemical changes that occur upon death, and preserve the gross form and appearance (Stoddard, 1989). They are known to affect the body weight and size of fish and invertebrates (Fox, 1996; Gaston et al., 1996; Jawad, 2003; Ajah and Nunoo, 2003). The variations (loss or gain) in body weight when the organism is preserved in different preservatives (Parker, 1963; Yeh and Hodson, 1975; Stobo, 1972) and changes in dry weight of estuarine macrofauna (Gaston et al., 1996) have been reported following preservation. Dramatic changes in weight for Sarotherodon mossambicus after preservation in * Present address: Department of Fisheries and Aquaculture, University of Veterinary and Animal Sciences, Lahore. 0030-9923/2008/0004-0249 $ 8.00/0 Copyright 2008 Zoological Society of Pakistan. both formalin and ethanol have been reported (Billy, 1982). The variation in body proportions of the fish during the period of preservation might be due to tissue water content and the ratio of white to red muscles (Leslie and Moore, 1986). There have been no studies on the effect of preservative on the biomass of marine fauna from Pakistan. The objectives of present investigation were to evaluate the effects of two commonly used preservatives, ethanol and formalin, on the biomass of invertebrate and vertebrate marine fauna; and to examine the relationship between fresh and preserved weight for biomass estimation. MATERIALS AND METHODS Three species of ocypodid crabs (Ilyoplex frater, Macrophthalmus bosci, Serenella indica) were collected from the Korangi creek mangroves, Karachi in March 2002. A total 120 crabs were initially weighed and then divided into ten lots, each of 12 crabs. Each lot was preserved in 70% ethanol, 1% formalin and 10% formalin (four crabs each) for ten weeks. Every week one lot (12 crabs) was scarified and weighed. Crabs were then dried at 70 o C for 24 hours in a laboratory oven (WTC, Binder) and dry weights noted. Penaeid shrimps (Fenneropenaeus