Thesis Abstract

Abstract
Clariid fish species are essential for food security and economic development in Nigeria, particularly in Kano State. However, there is a lack of comprehensive morphological and genetic characterization of these species, which hinders effective conservation and management strategies. In this study, two strains of Clariid fish species from Kano State were morphologically and genetically characterized using microsatellite markers. Morphological analysis revealed distinct differences in body shape, fin morphology, and pigmentation patterns between the two strains. These morphological differences suggest potential genetic divergence and adaptation to different ecological niches within the same region. Genetic analysis using microsatellite markers indicated significant genetic differentiation between the two strains, supporting the morphological findings. The genetic diversity within each strain was assessed, revealing moderate levels of genetic variation. The presence of private alleles in each strain suggests unique genetic signatures that could be important for local adaptation and evolutionary potential. Population structure analysis identified clear genetic clusters corresponding to the two strains, indicating limited gene flow between them. Furthermore, demographic history reconstruction indicated historical fluctuations in effective population sizes for both strains, possibly influenced by past environmental changes and anthropogenic activities. The results suggest that maintaining genetic diversity and preserving local adaptations are crucial for the conservation of Clariid fish species in Kano State. Overall, this study provides valuable insights into the morphological and genetic characteristics of two strains of Clariid fish species in Kano State, Nigeria. The findings contribute to the understanding of the evolutionary processes shaping the genetic diversity and population structure of these economically important fish species. The information generated from this study can be utilized for sustainable management practices, conservation efforts, and aquaculture development programs aimed at improving the resilience and productivity of Clariid fish populations in the region. Further research incorporating additional molecular markers and sampling from broader geographical areas is recommended to enhance our knowledge of the genetic diversity and evolutionary dynamics of Clariid fish species in Nigeria.

Thesis Overview

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).

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.