| || || Copeland, Lekima K. F.|
| || || Seasonality, habitats and micro-habitats of fish in wadeable streams of Nakorotubu, Ra, Fiji Islands|
Author: Copeland, Lekima K. F.
Institution: University of the South Pacific.
Award: M.Sc. Marine Science
Subject: Fishes -- Seasonal distribution -- Fiji -- Ra -- Nakorotubu, Fishes -- Habitat -- Fiji -- Ra -- Nakorotubu
Call No.: Pac QL 636 .5 .F5 C672 2013
Copyright:60-80% of this thesis may be copied without the authors written permission
Abstract: Research on the abiotic and biotic factors affecting fish in both large rivers and wadeable streams in Fiji is scarce. This research analyzes several mechanisms affecting fish in wadeable streams of Nakorotubu, Viti Levu, Fiji. Three streams were sampled during the wet and dry seasons and divided into lower, mid and upper reach. At each reach there were five replicate stations and within each station water quality, habitat and microhabitat data were collected. Fish were surveyed using a combination of electrofishing and beach seine. Data were analyzed using both univariate and multivariate statistical methods to elucidate factors affecting fish communities. A total of 677 fish were caught through electrofishing; 27 species of fish from nine families were collected representing 16% of the known freshwater and brackish water fish fauna of Fiji. For statistical analysis 24 species were analyzed due to the inability to identify pipefishes in-situ to species level. All pipefish species collected were lumped into the one genus based category Microphis spp. Spatial variation in fish assemblages were identified with a total of eleven species (46% of total) confined to the lower reaches of the three streams surveyed. Other species such as Eleotris fusca, E. melanosoma, Kuhlia rupestris, Anguilla marmorata, Redigobius leveri, and Sicyopterus lagocephalus, were ubiquitous throughout the reaches. Temporal changes in fish community structure across wet and dry season were noticeable for the three streams sampled. About fifteen species (63%) were observed in both seasons, while seven species (29%) were seen only in the dry season. In contrast two species (8%) were only found in the wet season, Anguilla obscura and Glossogobius illimis. In general, fish assemblages did not differ significantly between the two seasons. The abundance and species diversity of fishes in streams were significantly (p<0.05) affected by position in the catchment, with lower reaches having the highest diversity and abundance and decreasing moving upstream. The lower reach of the three streams possessed broadly similar fish assemblages; however, there was a strong break from mid and upper reach assemblages. This variation was due to differences in the hydrogeology of the catchment and within-stream barriers. Water quality data were correlated to the viii total abundance of fish per station and total species richness per station using Spearman’s Rho test. Overall, parameters such as conductivity, turbidity and pH had significant correlations (p<0.05) with the fish assemblages. Habitat and micro-habitat variables were tested and it was found that the altitude, canopy cover and volume of water d in a stream are highly significant (Monte Carlo test, p=0.002) factors regulating fish communities across the three streams. The variation in abundance of the four important freshwater food fishes, Kuhlia rupestris, Kuhlia marginata, Eleotris fusca, and Anguilla obscura of Fiji was best explained by the these three environmental variables in the analysis. The results of this study suggest that the volumes of flow and water quality are important for freshwater fish biodiversity. In Fiji these parameters are being affected by anthropogenic pressures. A number of watershed management projects have started in Fiji to address these pressures. This research also provided a baseline for stream and fish health in Nakorotubu, Ra and it is hoped that these will improve through the watershed management efforts.