This study aim to investigate the morphological and genetic characterization of strains of Clariid fish species in some river bodies in Kano Stateusing microsatellite markers.One hundred and seventy seven Clariid fish samples (Clariasgariepinus and Heterobranchuslongifilis)were collected from six rivers (Thomas, Ghari, Tiga dam, Duddurun Gaya, Karaye and Bagwai) in Kano state. Body weight, twenty-two morphometric characteristics and four meristic counts were measured on each fish sample to determine the influence of river location, strain of fish and sex.Body weight was measured in grams using sensory scale, the morphometric measurements were measured in centimetres using flexible tapewhile meristic counts were counted visually.The morphometric characteristics taken on the body were; Body weight (BW), Total length (TL), Standard length (SL), Pre-dorsal distance (PDD), Pre-anal distance (PAD), Pre-ventral distance (PVD), Pre-pectoral distance (PPD),Caudal peduncle depth (CPD), Body depth at anus (BDA); measurements taken on the fin were; Dorsal fin length (DFL), Anal fin length (AFL), Pectoral fin length (PFL), Pectoral spine length (PSL); measurements taken on the head region were;Dorso-caudal length (DDCF), Dorso-occipital length (DODF), Head length (HL), Head width (HW), Snout length (SNL), Inter-orbital distance (ID), Eye diameter (ED), Length of occipital fontanelle (OFL), Width of occipital fontanelle (OFW) and Snout-occipital length (DSO). The meristic counts were; Dorsal fin ray count (DFRC), Pectoral fin ray count (PFRC), Anal fin ray count (AFRC) and Caudal fin ray count (CFRC).The total length (TL) and body weight (BW) of each fish sample was used to compute Length-Weight relationships using the formula: W = log a + b log L and K = 100W/L3 was used to compute Condition Factor. Blood sample was taken from each fishsampleby severing the caudal peduncle and drained into FTA cards for DNA extraction, Polymerase Chain Reaction and electrophoresis to determine genetic variationbetween the Clariid fish populations. Data gotten from the morphometric measurements were analysed appropriately using GLM procedures of SAS 9.4 to show the influence of river location, strain, and sex, Duncan multiple range test was used for mean separation, Principal component analysis of SPSS was used for possible data reduction, and Genealex 6.4 software package was used to analyse the resolve bands from DNA extraction to determine their base pair and genetic variation. Body weight, morphometric measurements and meristic countswere significantly affected (P<0.01,0.05) by location
and strain while sex had effect (P<0.01, 0.05) only on total length, standard length, dorsal fin length, dorso-caudal length, caudal peduncle depth, anal fin length, head length, inter-orbital distance, eye diameter and length of occipital fontanelle. The equation for the length-weight relationship for the three strains were: C. gariepinus = -329.86+17.56TL andH. longifilis= -241.49+14.28TL.The condition factors showed varying degree of wellbeing of fish samples in their habitat (K = 0.37 to 0.89). Tiga dam had the best condition factor (0.81-0.89) followed by fishes caught in River Ghari (0.74-0.88). Pearson correlation analysis for all the variables measured showed that relationship between Body Weight and all the morphometric measurements were positive and significant. The ‗r‘ values ranged from low (0.23) to high (0.80) for BW/PDD and BW/DDCF. The other measurements had positive and significant relationships with values ranging from 0.30 for ED/SL to 0.92 for TL/SL. Principal component analysis indicated that most of the variables could be used for discrimination with regard to the species with a total variance of 82.52% shared as 47.66%, 19.16%, 8.67% and 7.03% for PC1, PC2, PC3 and PC4, respectively. Among the populations sampled, the genetic similarity ranged from 0.018 to 0.079 whilethe genetic distance ranged from 0.112 to 0.998. The Fst values ranged from
0.000 to 0.663, Fit ranged from -0.041 to 0.115, Fis ranged from -0.350 to -0.262. The result indicated a large number of gene flow (exchange) among the populations with a range of 0.455 to 0.866. The populations were not genetically pure but heterogeneous with varying degrees of genetic similarity and distance. Since there was no inbreeding as shown in the study, none of the population exhibited genetic uniqueness. The populations had a high genetic differentiation between populations but moderate differentiation within populations. The populations were outbred populations; an indication that relatives avoided mating in the population. There was an established magnitude of genetic divergence (91.86%) among the populations as shown by the result of the percentage polymorphism which depends on the number of alleles detected per locus and their frequencies. The study indicated that river location and species of fish had a significant influence on Clariid fish morphometric measurements and meristic counts. The study also gave an indication that the growth pattern of Clariid species in Kano State Rivers was positive allometric growth pattern (b>3) and the Clariid fishes are in good condition of wellbeing as indicated in the condition factor.
1.1 Animal Variation
Variability is the fundamental and basic characteristics of life. Every level of organization of life displays variation in some parameters, in space or time, within and between cells, tissues, organisms, populations and communities. The existence of variations in natural populations of organisms is a necessary condition for evolution. While variability is both a product and foundation of the evolutionary process, biologists are still confronted with the basic problems of explaining the nature, extent and causes of this web of complexity (Reynaldo and Cesar, 2014). Genetic variation is one key factor in the survival of species. Natural populations are perhaps the best gene banks which are critical resources for genetic variation for current and future application in improvement of farmed species of fish (Dunham, 2004). Morphological differentiation is one of the several approaches which have proved useful in studying variability. Morphological data alone, however, is insufficient to explain variability. Molecular biology, biochemical analysis and other methods coupled with morphology are powerful means in understanding variability and evolutionary relationships among and within populations of organisms (Reynaldo and Cesar, 2014).
Among populations, genetic diversity can also be gained when populations that are not normally in contact with another hybridize that is when isolated population experienced migration, gene flow and genetic drift. This can occur when physical barriers are removed such as when fishes are introduced to an area or escape, or when migration patterns changes due to environmental condition. Populations of many species of organisms may
respond differently, both morphologically and genetically, to a changed environment. Individuals tend to express different phenotypes (morphological, physiological or behavioural) when surviving in varied environments (Freeman and Herron, 1998). To this end, genetic studies of fish populations play an important role in the sustenance of genetic diversity (Seeb et al., 2007). Genetic markers can provide valuable information about geographic structuring, gene flow and demographic history of populations that can be highly relevant for conservation and management purposes (Maes and Volckaert, 2007).
Of all the animals and plants in the aquatic environment, fish is the most important source of human food (Yilmaz et al., 2000). Fish plays an important role in the development of a nation. Apart from being a cheap source of highly nutritive protein, it also contains other essential nutrients required by the body (Sikoki and Otobotekere, 1999). Fishes are highly important in the development of Nigeria both economically and health-wise as source of protein with low cholesterol level in the diets of many populace.Fish and fish products are economically significant as they provide jobs and investment opportunities and, for many countries, a means of improving the balance of international trade (Yilmaz et al., 2000). Fish is a high quality food and apart from its protein contents, it is also rich in vitamins and contains variable quantities of fat and minerals for human health (Adeniyiet al., 2010). Fish oil contains vitamins A, D, E and K which have been successfully used in controlling coronary heart diseases, arthritis, atherosclerosis, asthma, auto-immune deficiency diseases and cancer (Bhuiyan et al., 1993). Fish is often recommended for cardio-vascular disease patients because of its unique fat, which is composed mainly of Omega- 3 polyunsaturated fatty acid. In addition to its nutritious flesh, vitamins A and D present in fish oil are important especially for infants and children (Fasakin, 2006). Fish also supplies to the body, a range of inorganic minerals such as Phosphorus, Fluorine,
Potassium, Iron, Zinc, Magnesium, and Copper and in marine species Iodine as well as vitamins A and B complex (Adeniyi et al., 2010). The proximate composition, nutritive values and mineral composition of fishes in Nigeria have been documented (Olatunde, 1980; Abdullahi and Abolude, 2006; Dankishiya and Kabir, 2006; Abdulkarim and Abdullahi, 2009). Most of the fish used for human consumption is obtained through exploitation of wild populations.
Water quality tolerance of catfish is diverse due to environmental changes. The warmer the water, the less the dissolved oxygen likewise, the greater the altitude, the less the dissolves oxygen, causing severe cases and death aquatic organisms including catfish. According to F.A.O., (2003), water quality requirement for catfish are as follows; temperature – 26 to 32oC, dissolved oxygen – 3 to 10 mg/l or > 3ppm, pH – 6 to 8, Alkalinity – 50 to 250 mg/l, Ammonia – 0 to 0.03% and Nitrite – 0 to 0.6mg/l. It also reported that for advanced fry, the requirement are as follows; dissolved oxygen – 3-5ppm, temperature – 30oC, ammonia – 0.1 to 1.0ppm, nitrite – 0.5ppm, nitrate – 100ppm, pH – 6 to 9, carbon dioxide – 6 to 15ppm and salinity – 10 to 16ppt.
1.2 Statement of Research Problem
Reduction in the genetic resources of natural fish populations is an important management problem. Not only has the genetic diversity of many fish populations been altered, but many populations and species have been extirpated by pollution, overfishing, destruction of habitat, blockage of migration routes and other human developments (Ferguson, 1995). Loss of genetic diversity and locally adapted populations (and species) can compromise stability and recovery potential of marine ecosystems as well as impair their ability to adapt to changing environmental condition.There is generally limited information on
genetic variation amongand within Clarias and Heterobranchus species and this greatly hampers an efficient and sustainable exploitation of these resources (Worm et al., 2009).