Length-weight And Length-length Relationships Of Hybrid Catfish, Clarobranchus Reared At Different Stocking Densities
Chapter One
Introduction
1.1 Background of the Study
The place of fisheries in the nation’s drive for food security is both strategic and secure. Fish farming is described as a gold mine but fish seed propagation has been recognized as the gold miner, being the fastest and fattest revenue yielding aspect of fish farming in Nigeria (Effiong et al., 2012; FAO, 2014). Fingerling demand is enormous and estimated at over 4.3billion annually but less than 1.5billion are being produced (FDF, 2008). Madu (2008) identified adequate stocking densities to be one of the most important factors that must be considered in successful hatchery management. Successful aquaculture requires not only careful selection of species, appropriate feeding and water quality management but also to a great extent, the density to which the fish are stocked (Barua, 1990). Stocking density has also been described as important parameter in fish culture as the health; growth and survival of fish depend upon this factor (Shagunan, 1997).
Nigeria has a high potential to develop its fish farming to increase the amount of fish that is produced in the country because of its high demand and favourable scale price. The most cultured fish species in Africa especially in Nigeria are Clarias gariepinus(Eagle and Valderrama, 2001), Heterobranchus species (Ellis et al, 2002) and their hybrids. Under different culture systems, the above species exhibit different feed utilization efficiencies, growth performance, and disease resistance (Gamal et al., 2008). Previous investigation on growth response and survival rate of Clariid catfish, particularly Clarias gariepinus and Heterobranchus longifilis showed that both species exhibit fast growth and ability to withstand adverse condition in different culture systems (Viveen et al., 1985). Heterobranchus species has some advantages over Clarias species such as higher growth rate, feed conversion (Anibeze and Eze, 2000) and remarkable yield while Clarias species mature earlier and has higher fecundity (Nwadukwe and Nawa, 2000).
Aquaculture is a traditional farming practice in most parts of African including Nigeria and the potential of the African catfish had long been recognized in African aquaculture (FAO, 2005). Fish are generally considered good quality food for human consumption because of the balanced polyunsaturated fatty acid content. Culturable aquatic animals are safer products for human consumption than wild fish because they are raised in controlled environment where pollution could be well managed. Fish favour could be manipulated by dietary ingredients fed to the target species (Adekoya et al., 2006).
The most economically important form of aquaculture is fish farming, and industry that accounts for an ever increasing share of world currently at maximum sustainable yield. Since the late 1988s there has been a concerted effort to maintain global commercial harvest of ocean fish at approximately 100 million metric tons (mmt) (Wabnitz et al., 2003). However, as global population grows, demand for fish and shell fish increases and the percentage of aquatic products grown must likewise rise to meet the supply of those products. FAO (2007) projection for increased production are in range of 4 –100 mmt of new aquaculture production about the year 2030. There are over 25,000 species of fishes and there are estimates that 100 new species raised in relative to the total number available is an indication that aquaculture is a new concept in many parts of the world (FAO, 2009). There are only a few production systems in use for aquaculture and they include earthen ponds, race ways, cages, net pens, and indoor recirculating system. Earthen ponds or cages placed in existing bodies of water are the oldest production systems while the indoor recirculating system is the newest.
Successful aquaculture takes into considerations the biology of the aquatic species in terms of stocking density, feeding, water flow, temperature needed, disease prevention, system design, and others. Common products of aquaculture in Nigeria include catfish, tilapia and carp (Adewumi, 2005). The genus Clarias and their hybrids are cultured for their fast growth rate, disease resistance and ability to cope in high density culture related to their air breathing habit (Hulata, 2001). When stocking densities exceed the level at which pond biota can supply essential nutrients, higher feed inputs are needed as well as supplemental aeration cultured at high density and give a very high production per unit area. However, the availability of suitable feed with high protein content has been limiting the production of catfish (Jeje, 1992; Adekoya et al., 2006).
Knowledge of some quantitative aspects such as length –weight relationships and condition factor of fishes is an important tool for the study of fish biology. The condition factor in fish serves as an indicator physiological state of the fish in relation to its welfare. The studies of length – weight and length- length are widely practiced tool in fishery management for different purposes, especially in the study of population dynamics, ecology, taxonomic differences, event in life history like metamorphosis, maturity and stock management (Froese, 2006; Ferreira et al., 2008; Vaslet et al 2008). Consequently length-weight regression had been used frequently to estimate weight from length because direct weight measurements can be time consuming in the field (Sinovcic et al., 2004).
1.2 Statement of Research Problem
The culture preferences of Clarobranchus are similar to those of other catfish species in terms of water quality requirements. However, there is paucity of information available on the effects of stocking density on length-weight and length-length relationships of this catfish hybrid.
1.3 Justification of Study
The story of aquaculture in Nigeria is essentially the story of catfish culture and the hope of adequate fish supply in Nigeria hangs on its development and culture (FAO, 2009). Recent trends all over the world, point to a decline in landing from capture fisheries, an indicator that fish stock have approached or even exceeded the point of maximum sustainable yield. Aquaculture therefore remains the only viable alternative for increasing fish production in order to meet the protein need of the people. The information gained from this study would provide farmers and researchers with an understanding of effects of stocking density on length-weight and length-length relationships of hybrid catfish, Clarobranchus in cage culture system.
1.4 Aim and Objectives of the Study
The aim of the study was to assess the effects of different stocking densities on length-weight and length-length relationships in hybrid catfish Clarobranchus. The specific objectives of the study were to:
Assess the relationship between fish total length and body weights at different stocking densities.
Determine the relationship between fish standard length and body weights.
Estimate the relationship between adipose fin length and body weights at different stocking densities.
Develop a relationship between fish TL, SL and AFL at different stocking densities.
Leave a Comment