SEASONALITY, HABITATS and MICRO-HABITATS of FISH in WADEABLE STREAMS of NAKOROTUBU, RA, FIJI ISLANDS by Lekima K. F. Copeland Co

SEASONALITY, HABITATS AND MICRO-HABITATS OF FISH IN WADEABLE STREAMS OF NAKOROTUBU, RA, FIJI ISLANDS

Lekima K. F. Copeland

Cover photo: A possible new genus new species of pipefish in the family Sygnathidae found in Vucinivola stream, Nakorotubu.

A thesis submitted in fulfillment of the requirements for the Degree of Master of Science in Marine Science

School of Marine Studies Faculty of Science, Technology and Environment University of the South Pacific

September, 2013

DEDICATION

To my dearest grandmother Vani Tupou Koroi for her love and support

The Rosi ni Kuladrusi Samanunu Simpson

ACKNOWLEDGEMENTS

The stream flowing from the temple

“Wherever the stream flows, there will be all kinds of animals and fish. The stream will make the waters of the Dead Sea fresh, and wherever it flows it will bring life” (Ezekiel 47:9).

Shortly after submitting my thesis proposal to the research committee, I left to join an expedition to survey several streams originating from the highest peak in New Caledonia. In my heart I still doubted myself on whether I had the ability to undertake Master’s research. I remember lying restless in the early hours of the morning in a small hut far from civilization. Somehow this bible verse came to my mind and all I could remember was “the stream flowing from the temple” but I still could not recollect which book and verse. I switched on my head torch so that I could flip through the pages of my bible but to no avail; I still could not find it. I turned off my head torch and decided to get some sleep. Somehow my bible fell from my hands in the dark and a thought crossed my mind that I should flip it over and switch on the torch. Right before my eyes was the exact book and chapter (Ezekiel 47) I was looking for. Out of the 1220 pages in my bible it fell exactly on the page I was looking for. From that day onwards I knew that God had given his blessings for me to work on riverine fishes.

To my supervisors, Professor William Aalbersberg, Aaron Jenkins, James Comley, Marika Tuiwawa and Professor Linton Winder, thank you very much for the support and guidance throughout the study. I greatly appreciate the graduate assistant scholarship given to me by Professor Aalbersberg. I would not have been able to undertake this study without a scholarship and I am especially grateful to Marika Tuiwawa for allowing me to work at the South Pacific Regional Herbarium as a graduate assistant. It has been a blessing to travel with Marika and the rest of the herbarium team to some of the most beautiful and remote parts of Fiji.

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To Aaron Jenkins, I gratefully acknowledge the work you have done on Fiji’s freshwater fishes. Thank you for sharing valuable information on Fiji’s fishes, which included the provision of the fish-dex cards, fish keys, the use of the seine nets for my study and verifying my collection. I thank James Comley who has critiqued this research from the very beginning to the end. Your insight into the experimental design and the analysis of the results has helped me immensely in completing this thesis. Thank you Professor Linton Winder for your comments on the data analysis and results chapter.

My deepest recognition to the University of the South Pacific for funding this research. For the field work carried out in Nakorotubu, I would like to thank the Ra Provincial Office for allowing me to carry out the research in the province. Many thanks to the chiefs and village headmen of the following villagers, Nabukadra, Saioko and Naocabau for permission to undertake research on their qoliqoli. Especially to the Mata ni Tikina (district representative) for allowing us to stay in his house over the course of the fieldwork. Thank you Fiji Meteorological Service for providing rainfall data for this thesis.

My gratitude to my field assistants from the villages; Josh, Abo and Takala. To my two cousins Samu Copeland and Pita Koroi, thanks for assisting me with the field work in Nakorotubu.

To the Herbarium staff, thank you Alifereti Naikatini for helping out with the logistics in carrying out the fieldwork. To Hilda Waqa thank you for answering many questions concerning multivariate analyses using CANOCO. I gratefully appreciate the training in 2010 through the Darwin Initiative fund and thank you for allowing me to be part of that workshop. The training received helped me immensely in the multivariate component of my thesis. Dr. Sarah Pene thank you for your comments on the first draft of my thesis.

The staff of the environment unit, Dr. Bale Tamata, Ron Vave and Semisi Meo, thank you for allowing me to use the Horiba meter, underwater camera and the color printer to print my field protocol sheets. Thank you Leigh Anne Buleirua for allowing me to travel

iv with you guys to Nakorotubu under the COWRIE project for the first time. This visit helped me choose my sites for the study. Special thanks to Lavenia Tokalauvere and Hans Wendt for helping out with my maps. To the late Sese Gukivuli, thank you for the provisions of chemicals and water quality sampling equipment. To the staff at the administration office at IAS, Aisha Khan, Reshma Prasad, Loata Qorovarua and Rina Segran thank you for helping me out with the administration of my vote code. Special thanks to Mere Naisilisili our graphic artist for helping with several figures in my thesis; especially on the methodology figure.

To the staff of Marine Studies Program at the University of the South Pacific, Nanise Bulai, Jone Lima and Shiv Sharma, thank you for allowing me to use the facilities and equipments. Special thanks to the curator of the Marine Collection, Johnson Seeto for availing his pipefish book which was very useful for the identification of my pipefish specimens. Thank you again Johnson for allocating space in the marine collection to work on my voucher specimens and an environment that was conducive for writing my thesis. To Kara Roqica and Laisiasa Cavakilaqi thank you for your vehicles during the wet and dry season sampling phase. To my friends and peers in the CRISP room, Laura Williams, Monal Lal, Viliame Waqalevu and Kelly Brown for the many discussions concerning thesis work. To my fellow GAs at IAS, Siteri Tikoca, Bindiya Rashni, Mereia Katafono, Rusiate Ratuniyata, Fulori Nainoca, Hans Wendt, Isimeli Loganimoce, Elijah Tamata and Joape Ginigini thank you for your support.

To Kinikoto Mailautoka (KK) and David Boseto, thank you for sharing your knowledge on freshwater fishes with me. I remember my trip to the headwaters of the Wainibuka River in the Nakauvadra range with you KK, when I decided to try out a pretest of my thesis methodology. It was difficult because you were just critiquing me very well on my data collection only after one station. I sat there dumbfounded and stressed but the lessons learnt (two blisters on my left and right calf muscles) taught me valuable life lessons and prepared me well for data collection in Nakorotubu. Thank you KK and David for always asking me “Hey Lex, what fish is this?” and when I got it wrong you

v guys would always correct and clarify things with me. This was the fastest way I could learn how to identify freshwater fishes in Fiji.

Finally, to my very supportive family, especially my grandmothers Vani Koroi and Elizabeth Copeland, my mom and stepfather Litia and Venasio Ramabuke, my siblings Michael Copeland, Vani Copeland, Josephine Copeland and Patrick Ramabuke. To my cousins Arthur Sokimi, William Sokimi, Augustine Sokimi and Lycyna Sokimi; Leslie Copeland, William Copeland and Samu Copeland. To Aunty Josephine and Uncle William Sokimi, Aunty Etrina Simpson, Uncle William Copeland and Aunty Lucy Copeland and the rest of the family and friends thank you for your support thus far.

God bless you all and Vinaka Vakalevu.

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 micro- habitat 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

vii 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.

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ABBREVIATIONS AND ACRONYMS COWRIE Coastal and Watershed Restoration for the Integrity of Island Environments

CRISP Coral Reef Initiative in the South Pacific

EEZ Exclusive Economic Zone

IAS Institute of Applied Sciences

IUCN International Union for the Conservation of Nature

HIES Household Income and Economic Survey

MEA Millennium Ecosystem Assessment

MPAs Marine Protected Areas

PCA Principal Component Analysis

PERMANOVA Permutational Multivariate Analysis of Variance

PICTs Pacific Island Countries and Territories

RAP Rapid Assessment Project

RDA Redundancy Analysis

SES Socioeconomic Survey

USP University of the South Pacific

WHO World Health Organization

TABLE OF CONTENTS DECLARATION OF ORIGINALITY ...... i DEDICATION ...... ii ACKNOWLEDGEMENTS ...... iii ABBREVIATIONS AND ACRONYMS ...... ix TABLE OF CONTENTS ...... x LIST OF FIGURES ...... xiii LIST OF TABLES ...... xiii Chapter 1 Introduction and literature review ...... 1 1.1 General introduction on freshwater resources ...... 1 1.2 Global threats to freshwater fish biodiversity ...... 2 1.3 Global freshwater fish biodiversity and ecoregions ...... 3 1.3.1 General considerations ...... 3

1.3.2 Freshwater fish diversity ...... 4

1.3.3 Freshwater ecoregions ...... 5

1.4 The uniqueness and importance of fish in the Oceania region ...... 5 1.4.1 Oceania islands freshwater fish assemblages...... 5

1.4.2 The significance of fish to Oceania countries ...... 6

1.5 Fiji’s freshwater fishery ...... 7 1.5.1 Cultural significance of freshwater fishery and fish in Fiji ...... 7

1.5.2 Insular ichthyological research in Fiji ...... 8

1.6 Threats to Fiji’s inland waters and the need for conservation ...... 9 1.6.1 Deforestation in Fiji ...... 9

1.6.2 The threat of invasive species, in-stream barriers and chemicals to Fiji’s freshwater fish ...... 10

1.7 Factors affecting freshwater fish assemblages ...... 10 1.7.1 Spatial and temporal variation ...... 11

1.7.2 Predation ...... 12

1.7.3 Riparian zone linkages ...... 12

1.7.4 Natural disturbances ...... 13

1.7.5 Physical and chemical conditions ...... 13

1.8 The framework of ecological guilds ...... 14 1.9 Aims and structure of this thesis ...... 15 Chapter 2 Study region ...... 16 2.1 Location ...... 16 2.2 Fiji’s climate ...... 17 2.3 Nakorotubu geology and geomorphology ...... 18 2.4 Nakorotubu climate ...... 18 2.5 Biodiversity and conservation work in the Nakorotubu range ...... 19 2.5.1 Rapid assessment project ...... 19

2.5.2 Marine conservation efforts in Nakorotubu ...... 20

2.5.3 Watershed management in Nakorotubu ...... 20

Chapter 3 Methodology ...... 22 3.1 Biological study ...... 22 3.1.1 Stream characterization ...... 23

3.1.2 Data collection ...... 23

3.1.3 Habitat sampling strategy ...... 24

3.1.4 Fish sampling ...... 26

3.2 Fish identification and preservation ...... 27 3.3 Fish life history and feeding characteristics ...... 28 3.4 Data handling and analyses ...... 28 3.4.1 Fish community structure ...... 28

3.4.2 Fish diversity ...... 29

3.4.4 Fish environmental relationships ...... 30

Chapter 4 Results ...... 33 4.1 Electrofishing catch composition ...... 33 4.2 Life history and feeding guilds ...... 37 4.3 Longitudinal distribution of freshwater fish in Nakorotubu ...... 38 4.4 Exploratory analysis ...... 39 4.5 Fish community structure analyses ...... 40 4.6 Fish species diversity index ...... 43

4.7 Shannon Wiener diversity analyses ...... 43 4.8 Habitat and microhabitat data ...... 45 4.8.1 Velocity, canopy cover, wetted width and stream depth ...... 45

4.8.2 Substrate cover ...... 48

4.8.3 Water quality parameters ...... 50

4.9 Ecological-environmental relationships ...... 54 4.9.1 Water quality and fish community ...... 54

4.9.2 Habitat, micro-habitat data and fish assemblage ...... 55

Chapter 5 General Discussion ...... 58 5.1 Spatial variation in fish assemblages ...... 58 5.2 Seasonal shifts in fish assemblages ...... 62 5.3 Fish assemblages and environmental factors ...... 65 5.3.1 Water quality ...... 65

5.3.2 Freshwater fish habitat and micro-habitat associations ...... 66

5.4 Study considerations ...... 67 5.5 Limitations of the study ...... 69 5.6 Conclusion and recommendations ...... 70 Chapter 6 References ...... 73

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LIST OF FIGURES Figure 1-1 Nested hierarchal screening of global fish fauna that determine the species composition within a lake or stream...... 11 Figure 2-1 The study region of Nakorotubu district, situated on the northern coast of the island of Viti Levu ...... 17 Figure 2-2 Total monthly rainfall taken from nearest Fiji Meteorological Station in Penang, Rakiraki...... 19 Figure 3-1 Sampling stations (n=80) in wet and dry season survey...... 22 Figure 3-2 Experimental design of study carried out in Nakorotubu for wet and dry season sampling...... 24 Figure 3-3 In-stream sampling protocol. Note that yellow boxes indicate quadrat where substrate and depth readings are taken...... 26 Figure 3-4 Electrofishing in conjunction with a beach seine net...... 27 Figure 4-1 Total abundance of each fish species caught in the wet and dry season, pooled across the three streams surveyed...... 34 Figure 4-2 Nakorotubu streams ichthyofauna life history categories ...... 37 Figure 4-3 Feeding guilds of the ichthyofauna sampled in Nakorotubu...... 38 Figure 4-4 Longitudinal distribution of stream fishes from lower reaches to headwaters (n=80)...... 39 Figure 4-5 Multi-dimensional scaling plot of the presence/absence of species within reaches of each stream surveyed across wet and dry season...... 40 Figure 4-6 Shannon Wiener diversity index for the three streams measured across wet and dry season...... 43 Figure 4-7 Box and whisker plots showing median differences in stream velocity, canopy cover, wetted width and stream depth sampled across reach and season...... 46 Figure 4-8 Mean substrate cover in Vucinivola stream (mean ± S.E)...... 48 Figure 4-9 Mean substrate cover in Taveu stream (mean ± S.E)...... 49 Figure 4-10 Mean substrate cover in Nakawaqa stream (mean ± S.E)...... 49 Figure 4-11 Box and whisker plots showing median differences in water quality parameters sampled across reach and season...... 51 Figure 4-12 Species-environment biplot diagram from the PCA ...... 56 Figure 4-13 Species-environment biplot from the RDA summarizing differences in fish assemblages along the three environmental variables...... 57

LIST OF TABLES Table 3-1 Substrate classification for in-stream habitat measurements modified according to the Wentworth Scale...... 25 Table 3-2 Length of gradient based on DCA, indirect gradient analysis...... 31 Table 4-1 Checklist of fishes in the three streams surveyed...... 35 Table 4-2 PERMANOVA results on the presence absence data examining the effects of season and reach within stream...... 40 Table 4-3 PERMANOVA pairwise tests for the effect of season on community structure...... 41

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Table 4-4 PERMANOVA pair-wise tests of the effect of reach within stream conducted in wet and dry season on fish presence/absence. t...... 42 Table 4-5 PERMANOVA results on the Shannon Weiner diversity data examining the effects of season and reach within stream...... 44 Table 4-6 PERMANOVA pair-wise test on the effect of reach within a stream on Shannon Weiner diversity...... 44 Table 4-7 Correlation summary table of environmental parameters versus abundance of fish per station...... 54 Table 4-8 Correlation summary table of environmental parameters versus fish species richness per station...... 55 Table 4-9 Summary table of PCA output in CANOCO...... 55 Table 4-10 Summary table of RDA in CANOCO...... 56

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Chapter 1 Introduction and literature review

1.1 General introduction on freshwater resources Water is a fundamental resource required to sustain life on Earth. It provides a source of energy, a medium for transportation, and habitat for biota (Dudgeon et al., 2006; Wetzel, 1992). Water covers over 71% of the Earth’s surface and over 99 % of it occurs in the oceans (Wetzel, 1992). Hence, the difficulty of people extracting this resource for direct consumption and use on land arises. Furthermore, the only major sources sensible for humankind to extract, are surface and groundwater supplies (Wetzel, 1992).

The Earth’s freshwater resource constitutes only 0.01 % of the world’s water and covers 0.8 % of the Earth’s surface (Polhemus et al., 2008). This relatively small amount understates its fundamental importance in the maintenance and survival of terrestrial life. Although fresh water covers only 0.8% of the earth’s surface it supports almost 6% of the earths biodiversity (Hawksworth & Kalin-Arroyo, 1995). The organisms contained in fresh water represent valuable natural resources in economic, cultural, aesthetic, scientific, and educational terms; and therefore, it is in the interest of all humans, nations, and governments that they are conserved and managed (Naiman & Dudgeon, 2011).

Freshwater ecosystems are considered to be the most altered by anthropogenic actions of all the broad ecosystems types, primarily due to declines in water quality and the loss and fragmentation of wetlands (MEA, 2005). Nonetheless, declines in biodiversity in heavily impacted terrestrial and marine ecosystems are far less compared to those in the freshwater environments (Argent et al., 2003; Cooke et al., 2005; MEA, 2005). To put things into perspective, Naiman (2008) states that based on the recent Millennium Ecosystem Assessment (2005); freshwater biodiversity from 1970 to 2002 declined ~ 55%, compared to ~ 32% each for terrestrial and marine systems. This is primarily due to the uneven richness of inlands waters as habitats for plants and animals (Dudgeon et al., 2006).

Burgeoning human populations around the world have led to increased consumption and more waste output. This has also led to unprecedented and mounting threats to the biodiversity of 1

freshwater. The freshwater resources on planet Earth are collectively experiencing markedly accelerating rates of degradation (Dudgeon et al., 2006; Wetzel, 1992). The changes in freshwater flow regimes through water resource developments are altering freshwater fauna life histories, threatening the existence of thousands of species (Dudgeon et al., 2006). To curb these problems, the exponential human growth and utilization of freshwater must be effectively addressed by mankind (Wetzel, 1992).

This will entail the general recognition of the catchment as the focal management unit (Dudgeon et al., 2006) to preserve hydrological connectivity and ecosystem intactness. Since freshwater systems are one of the most productive ecosystems and maintain large fisheries in different parts of the world, the United Nations as part of its contribution to the Millennium Development Goals (MDGs) and Agenda 21 have declared 2005-2015 as the International Decade for Action “Water for Life” (Dudgeon et al., 2006). A recent publication by FAO (2012) shows that capture production from inland water continues to grow, with an estimated 11.2 million tonnes in 2010. This is an increase of 1 million tonnes since 2008.

1.2 Global threats to freshwater fish biodiversity Humankind is entering a human dominated, geological epoch called the Anthropocene (Zalasiewicz et al., 2008); in light of this Dudgeon et al. (2006) state that there are five grouped interacting threats on global freshwater biodiversity, over-exploitation, water pollution, habitat degradation, species invasion, and flow modification . In their review Dudgeon et al. (2006) effectively convey the idea that “the medium is the message”, where the vulnerability of freshwater biodiversity is due to the fact that freshwater is a resource that may be extracted, diverted, contained or contaminated by humankind, in turn undermining its importance as habitats for aquatic flora and fauna.

Fishes and other animals are overexploited on a global scale for inland waters (for a review see Allan et al., 2005), though extraction continues to grow globally for fish and fishery products; however, over the last decade capture fisheries harvest has stagnated (Allan et al., 2005). The impacts of exotic species provide an additional problem for the biodiversity of inland waters. The impacts of introduced tilapia, mosquito fish and trout on native fishes of Oceania are good

examples(Jenkins et al., 2010; McDowall, 2006). Superimposed and/or compounding these threats are climate change, which leads to increased temperatures and shifts in runoff and precipitation patterns (Dudgeon et al., 2006). A study by Eaton & Scheller (1996) on the thermal habitats of 57 species in the United States found that due to climate warming, approximately 50% of habitats for cold and cool water fish could be reduced. In Australia the adaptive capacities of many freshwater fish species will be outpaced by the rate and magnitude of projected climate change, consequently those with a specific niche or limited range are more susceptible to changes (Morrongiello et al., 2011).

Water pollution is a pandemic problem, excessive nutrient enrichment and other chemicals such as endocrine disrupters are increasing (Dudgeon et al., 2006). This problem is further exacerbated due to inland waters characteristically lacking the volume of water to dilute contaminants or mitigate other impacts compared to that of open marine waters (Dudgeon et al., 2006).

Fragmentation of river ecosystem by dams is present in a majority of the world’s large rivers, consequently altering migration patterns and converting free-flowing rivers to reservoir habitat (Jager et al., 2001). For instance, the upstream migration of fishes or shrimps that breed in marine environments are blocked due to downstream dams, therefore leading to extirpation of whole assemblages in headwaters (Pringle, 2001). Due to the risk of management failure been so large, the combination of factors aforementioned places freshwater ecosystems unparalleled among the environmental priorities for science funding (Ormerod et al., 2010).

1.3 Global freshwater fish biodiversity and ecoregions

1.3.1 General considerations Fish is a generic word in the sense that it “is applied to a diverse grouping of aquatic chordates comprised of hagfishes and lampreys, sharks, rays and chimaeras, and the finned bony fishes” (Lévêque et al., 2008). Finned bony fishes are the most diverse group and are well represented in fresh water, while the remaining groups are predominantly marine (Lévêque et al., 2008). Tropical and subtropical regions contain most of the species whilst there is a general decrease in 3

diversity towards temperate and polar regions (Lévêque et al., 2008). Glaciations have resulted in areas such as North America, Europe and Asia having a tendency of relatively depauperate fish fauna (Lévêque et al., 2008).

1.3.2 Freshwater fish diversity Knowledge on global fish diversity remains woefully incomplete as there is disagreement on the number of fish species and that hundreds of new species are being found and described every year. For freshwater fish the number of valid species varies across the literature. For example, Lunderberg et al. (2000) states that approximately 41% (over 10,000) fishes are found primarily in freshwater; moreover, about 250 fish species traverse between freshwater and marine environments (McDowall, 1997, 2008). However, this number has surely increased with recent amphidromous fish species being discovered and being described in the Oceania region (Jenkins et al., 2008; Keith et al., 2007; Larson, 2010). Furthermore, if other fauna are to be added such as amphibians, aquatic reptiles, and mammals to this freshwater fish total, then it becomes clear that one third of vertebrate species are confined to freshwater (Polhemus et al., 2008).

The current Fishbase data provide an even higher estimate of 45% (13,000 freshwater fish species) compared to the 16,000 fish species that live in marine habitats (Lévêque et al., 2008). Nelson (2006) suggested a total of almost 28,000 species (freshwater and marine). Remarkably, an estimated 13,000 freshwater species live in lakes and rivers that cover only 1% of the earth’s surface compared to 16,000 species living in marine habitats, which cover 70% of the earth (Lévêque et al., 2008).

Eschmeyer et al. (2010) have established a catalogue of fishes which has been maintained for 25 years and provides a global estimate, with about 16,764 valid marine fish species and 15,170 freshwater fishes which brings a combined total of 32,042 fishes. The most recent update on the number of valid fish species as of 2nd October 2012, is 32,454 (Eschmeyer & Fong, 2012).

1.3.3 Freshwater ecoregions Abell et al. (2008) presented a new map that depicted the global regionalization of Earth’s freshwater system. They defined a freshwater ecoregion “as a large area encompassing one or more freshwater systems with a distinct assemblage of natural freshwater communities and species” (Abell et al., 2008). Additionally, within a given ecoregion, freshwater fauna, dynamics and environmental conditions, are more similar to each other compared to surrounding ecoregions and together form a conservation unit (Abell et al., 2008). Of the 13,400 described freshwater fish species, over 50% (6,900 fishes) were endemic to single ecoregions (Abell et al., 2008). These new ecoregion maps based on preliminary data of freshwater fish species at the ecoregion level revealed previously unrecognized areas of high biodiversity, highlighting the advantage of looking at the world’s freshwater resources through a new framework (Abell et al., 2008).

1.4 The uniqueness and importance of fish in the Oceania region

1.4.1 Oceania islands freshwater fish assemblages Oceanic islands of the Pacific are distinct from continental land masses in that they have developed unique freshwater fish assemblages that have important ecological linkages between marine and freshwater environments (McDowall, 1998b). Furthermore, species on most oceanic islands are predominantly marine and have adapted to freshwater (Lévêque et al., 2008). The isolation of the fauna has led to speciation(McDowall, 1998a). Amphidromy is a characteristic life history trait present on small oceanic islands of the tropics and sub-tropics (Keith, 2003); spawning occurs in fresh water and then the free embryos drift downstream to the sea where they spend several weeks to a few months of feeding and growing at sea before returning to rivers to grow and reproduce (McDowall, 2007, 2010). Tropical and sub-tropical islands of the Pacific have about seven families of fishes that occur frequently in freshwater streams of oceanic islands, however four families, Anguillidae, Eleotridae, Gobiidae and Kuhliidae, are the predominant families on oceanic island streams (Fitzsimons et al., 2002; pers. obs.). The two families Gobiidae and Eleotridae occur across multiple habitat types (Jenkins pers. comm., 2010). They are ubiquitous in geographic range and are predominant components not only in

Pacific streams, but elsewhere in the world’s tropical and sub-tropical regions (Fitzsimons et al., 1996).

1.4.2 The significance of fish to Oceania countries FAO (2010) reports that globally, a total catch of 10 million metric tonnes was from inland fisheries in 2008, exclusive of aquaculture harvest and recreational fishing. Of this total, the Oceania accounted for less than 1% (FAO, 2010). There has been a fourfold increase, around 3 % annually since data were first compiled in 1950 (Allan et al., 2005). Although the Oceania contribution to total inland fisheries capture may seem minute when adjusted for land area, Fiji and other Melanesian countries are significant areas for freshwater fish diversity on a global scale (Abell et al., 2008). Dependency on fish as a source of protein is high in Fiji and other Pacific island countries (Bell et al., 2009). For example, the flagtails (Kuhlia spp.), several gudgeons from the family Eleotridae and gobies (Gobiidae), freshwater eels (Anguilla spp.) are important sources of protein for rural populations in Fiji (Nandlal, 2005; pers. obs.).

For good nutrition 0.7 g of protein per kg body weight per day, derived from a variety of sources, is needed to prevent nutrient deficiencies (FAO, 1985; 2002 cited in Bell et al., 2009). Fish account for 15.7% of global population intake of animal protein and 6.1% of all protein consumed in 2007 (FAO, 2010). Fish are a major source of protein for the Oceania region as with per capita consumption at 25.2 kg making it one of the highest in the world in comparison to the global average of 17 kg (FAO, 2010). Notwithstanding the recent FAO (2010) per capita consumption for the Oceania, a study by Bell et al. (2009) between the year 2001 to 2006 conducted in fifteen Pacific Islands Countries and Territories (PICTs) using information from Household Income and Economic Survey (HIES) revealed how remarkably high fish consumption is in the PICTs. According to Bell et al. (2009) six countries in Micronesia and Polynesia have at least twice the level needed to supply approximately 50% of their recommended protein requirements. Nevertheless, fish consumption was much less in rural inland areas of PNG, and to some extent Solomon Islands due to poor access to fish in inland areas (Bell et al., 2009).

In 2007, the total value of fisheries and aquaculture production was estimated to be over $2 billion dollars in the region (Gillett, 2009). The freshwater fishery was totaled at 23,858 tonnes and valued at $23,115,025 (Gillett, 2009).

1.5 Fiji’s freshwater fishery National and international policies or priorities for development often inadequately address and undervalue inland fisheries (FAO, 2010). The bulk of work conducted on Fiji’s fishery has focused largely on the marine, coastal, and offshore fisheries resources (e.g., Gillett, 2010; Hand et al., 2005) but there has been scant attention paid to the economic value of Fiji’s inland fisheries. Local work has primarily focused on the mussel Batissa violacea, which is the major inland species of commercial importance. Richards (1994) reported that it is the largest single domestic fishery in Fiji, producing approximately 1,300 metric tonnes annually. Furthermore, its value has been estimated to be around FJD $1 million annually (Ledua et al., 1996). Other inland fisheries such as freshwater prawns (Macrobrachium spp.) and fish are at the subsistence level and there is no estimate of the amount of catch (FAO, 2002). However, the most recent estimate by Gillett (2009) reports that annual freshwater fisheries total harvest for the year 2007 was 4146 tonnes which was valued at $6,860,000 FJD.

1.5.1 Cultural significance of freshwater fishery and fish in Fiji Fishing was initially undertaken in rivers, ponds, wetlands and lagoons, long before humans started to grow crops or raise livestock (FAO, 2010). Venture onto large lakes or the sea happened many decades after in purpose built craft (FAO, 2010). Since time immemorial Fijians have had a profound understanding and reverence towards the land and its resources. In Fiji there exists a long established system of traditional fishing grounds called iqoliqolis. These traditional fishing grounds are under control of the communities adjacent to them based on a system of customary tenure, which is to have control over an inshore marine or insular freshwater area, and this is informally recognized by villagers and chiefs. There are 385 marine and 25 freshwater iqoliqolis in Fiji (Aalbersberg et al., 2005). Fijians have practiced traditional methods of preserving their food sources, such as temporary no-take areas and seasonal bans (Aalbersberg et

al., 2005). For example, in the village of Viria, located in the province of Naitasiri, the villagers have a no-take area in front of the village, where they have put in place a ban on the freshwater mussel Batissa violacea (Lamarck, 1818) and as anecdote villagers believe that a shark guards the tabu area (most likely a Bull shark, Carcharhinus leucas (Müller & Henle, 1839). The ban can only be lifted when the high chief from the island of Bau craves for freshwater mussel and it is the traditional obligation of woman from Viria village to fish for the mussels in the tabu area, which will be later accorded a traditional presentation to the high chief.

Furthermore, adoption of totems that identify themselves with animals and plants is a norm for most Fijians. In Fiji there is a traditional obligation called “veitabuki”; where certain food cannot be eaten in the presence of a traditional relative. For example, in the village of Delailasekau in the province of Naitasiri their totem are the freshwater eels from the genera Anquilla spp. and if someone from the village of Wainimakutu (Namosi province) is present, then they cannot eat the freshwater eel while the others cannot eat pork (pers. obs).

1.5.2 Insular ichthyological research in Fiji For Fiji the recent checklist by Seeto and Baldwin (2010) reports 33 marine endemic fishes. Jenkins (2009a) provides a synopsis of past icthyological work carried out in Fiji’s rivers by various researchers who together were able to catalogue 75 species and one endemic species for the Fiji Islands. Recent studies spanning the first decade of the 21st century by various researchers (Boseto, 2006; Boseto & Jenkins, 2006; Jenkins & Boseto, 2005; Jenkins & Jupiter, 2011; Jenkins et al., 2010; Jenkins & Mailautoka, 2010; Larson, 2010) have all contributed new findings on Fiji’s freshwater fish biodiversity and the factors affecting these faunal assemblages. For instance, there are a total of fourteen endemic insular fish in Fiji, nine are recorded in Jenkins et al. (2010) and the additional five are provided by Jenkins (pers. comm. 2010). However, much of the survey work has been focused on the three largest islands (Viti Levu, Vanua Levu & Taveuni) and with further work to be conducted in Kadavu and Lomaiviti group it is likely that new information will be gathered for Fiji’s freshwater fish biodiversity.

1.6 Threats to Fiji’s inland waters and the need for conservation The connection between forested watersheds, freshwater and marine resources, is widely recognized in Fiji and other regions (Haynes, 1999; Jenkins & Jupiter, 2011; Jenkins et al., 2010). For instance, the juvenile or sub-adult stages of many commonly harvested marine species occur in freshwater or low saline environments (Allen, 1991; Boseto, 2006; Jenkins & Jupiter, 2011; Jenkins et al., 2010; Jenkins & Mailautoka, 2010). These include snapper (Lutjanus spp.), trevally (Caranx spp.), grouper (Epinephelus spp.), sweetlips (Plectorhinchus spp.), mullets (Liza spp., Valamugil spp., Mugil cephalus), and even several sharks (Carcharhinus leucus, Sphyrna spp).

The connectivity of Fiji’s freshwater fish assemblages with the marine environment requires a holistic management of migratory pathways (ridge to reef). In Fiji 98% of freshwater fishes use the marine habitat during their lifecycle (Jenkins et al., 2010). The biodiversity of Fiji’s freshwater fauna are increasingly threatened in many places because of infrastructure development, agricultural development, logging activities, loss in forest catchment cover, and the introduction of exotic species (Haynes, 1999; Jenkins et al., 2010).

1.6.1 Deforestation in Fiji With a land area of 1,827,200 ha, the total forest cover in Fiji is about 852,990 ha (Lal & Tuvou, 2003) which is about 47% forest cover. Indigenous forests comprise 739,340 ha while hardwood plantations cover 51,490 ha and softwood (pine) 43,200 ha (Lal & Tuvou, 2003); this also includes a significant area of mangrove forest around 42,000 ha (ITTO, 2006). Moreover, “deforestation in Fiji is moderate but continuing” (Evenhuis & Bickel, 2005). Deforestation is common in lowland areas but small pockets of native fauna and flora remain in protected areas such as the Sigatoka dunes (Evenhuis & Bickel, 2005). According to Watling and Chape (1992 cited in Evenhuis & Bickel, 2005) an estimated 90,000-140,000 ha (11-16%) of the nation’s forests have been converted to non-forest land use since the mid 1960s. Forest loss is the most serious threat to the endemic fauna and flora of Fiji and other Pacific islands (Evenhuis & Bickel, 2005; Haynes, 1999; Jenkins & Jupiter, 2011).

1.6.2 The threat of invasive species, in-stream barriers and chemicals to Fiji’s freshwater fish Jenkins et al. (2010) found a significant correlation between presence of tilapia and decline of native freshwater species richness in Fiji. .Mid-reach sites with established tilapia populations have on average seven fewer species of amphidromous fish species compared to mid-reach sites with no tilapia (Jenkins et al., 2010). A recent survey in Vanua Levu that was looking into linkages between catchment, riparian vegetation and in-stream conditions found that in places where there was good forest cover they found very few species in the river systems. This was primarily due to hanging road culverts that had a drop of 1 – 2m and as a result acted as a barrier for fish migration (Jupiter et al., 2012). The use of chemicals such as detergents, pesticides and traditional fish poisons (derris roots) is rife in inland fisheries (pers. obs.). Although capture of target species may seem efficient this method is highly unselective and environmentally unfriendly.

1.7 Factors affecting freshwater fish assemblages Millions of years of changes in the global water cycle has shaped the present freshwater fish distribution (Lévêque et al., 2008). A long rich history exists between ecological communities and the study of their structuring factors (Jackson et al., 2001). Hence, an underlying subject in both fish biogeography and fish community ecology is understanding the factors that shape species richness patterns across different spatial scales (Jenkins & Jupiter, 2011). Figure 1-1 illustrates how these community structures of fish have been studied at nested hierarchical scales that look into broad geographical scales (among regions) down to a finer local scale (within a river), (Arrington & Winemiller, 2003; Smith & Powell, 1971). Studies include biogeographical histories and their relation to the distribution of freshwater fishes (Fitzsimons et al., 2002; McDowall, 1998a, 2003); trophic feeding guilds (Aarts & Nienhuis, 2003; Elliott et al., 2007); species richness (Reyjol et al., 2007; Whittaker et al., 2007); introduction of exotic/invasive fish species (Canonico et al., 2005; Jenkins et al., 2010; Vitule et al., 2009) ; reduction in forest catchment cover (Jenkins & Jupiter, 2011; Jenkins et al., 2010); and natural disturbances (e.g. Hurricanes; Vrancken & O’Connell, 2010).

Figure 1-1 Nested hierarchal screening of global fish fauna that determine the species composition within a lake or stream. Adapted and redrawn from the hierarchal filtering by Smith and Powell (1971).

1.7.1 Spatial and temporal variation Within a river system, lateral and longitudinal gradients in species richness and community composition are generally apparent (Jenkins & Jupiter, 2011; Lamouroux et al., 2002). The terminal or lower reaches of rivers in the Oceania contain the highest freshwater fish diversity (Boseto & Jenkins, 2006; Boseto et al., 2007; Jenkins & Jupiter, 2011; Jenkins & Mailautoka, 2009). The position in the catchment has been shown to be significant in determining freshwater fish community structure (Jenkins & Jupiter, 2011; Pusey et al., 2000). Spatial variability can be regulated by seasonal cycles of flooding and drying (Jenkins & Jupiter, 2011).

A study conducted in a tropical savanna during both wet and dry seasons on small fish inhabiting two water bodies by Prejs & Prejs (1987) found that during the wet season when the water level was high and food was abundant, the majority of fish species fed predominantly on vegetation dwelling invertebrates. However, during the dry season where there was a drastic decline in

invertebrate food, most fish species switched to alternative foods such as algae and detritus (Prejs & Prejs, 1987). The flooding size has been shown to be of overall importance in riverine communities. Lindholm et al. (2007) established that large and long lasting floods resulted in improved circulation and enhanced reproductive success for stream fishes, while low flood events meant higher volume-specific production at the base of the food web.

1.7.2 Predation The role of predation in structuring fish assemblages has been shown to be very strong via direct and indirect mechanisms (Jackson et al., 2001). In Palau researchers found when the piscivorous Kuhlia are eliminated due to their inability to surmount natural barriers such as waterfalls, because they are not morphologically adapted, small gobies became more abundant. The same trend was noticed for river shrimp (Macrobrachium spp.) at sites without Kuhlia rupestris (Nelson et al., 1995). Their findings suggest that predation by the mountain bass has considerable influence on the longitudinal distribution of freshwater fishes and invertebrates of Palau (Nelson et al., 1995). Furthermore, Werner et al. (1983) have shown that predation can affect habitat selection by prey species in rivers. Hence, pools or riffles may have different species assemblages due to prey species moving to sites with a lower risk of predation (Jackson et al., 2001).

1.7.3 Riparian zone linkages In the last two decades considerable global research effort have been focused on understanding the dynamics and management of riparian zones (Naiman et al., 2000). The linkages between the riparian zone and freshwater fish communities have been extensively studied (Bunn, 1993; Bunn et al., 1999; Pusey & Arthington, 2003). As Pusey & Arthington (2003) state it is not surprising that variation in riparian cover have been linked to spatial and temporal variation in fish assemblage composition. Pusey & Arthington (2003) in their paper provide several key examples of how riparian shade regulates the transfer of solar energy to aquatic ecosystems. For instance poikilothermic organisms such as fish will have their metabolic rates affected, which therefore influences their growth and allocation of resources for reproduction, both of which have fitness consequences, and ultimately, determine population size (Jobling, 1995 cited in Pusey &

Arthington, 2003). Jupiter and Marion (2008) summarized the important functions in addition to shading in terms of: (1) providing allochthonous production as food sources for downstream communities through lead litter debris; (2) providing important habitat structure for freshwater fish communities through tree and branch falls; and (3) by maintaining water quality.

1.7.4 Natural disturbances Organisms have evolved traits over evolutionary time that enabled them to survive, exploit and even depend on disturbances (Lytle & Poff, 2004). A key component of most intact ecosystems are natural disturbances (Lytle & Poff, 2004). Ecologically important ones are fires, floods, droughts, storms and disease outbreaks as they regulate population size and species diversity across spatial and temporal scales (Lytle & Poff, 2004). Fish assemblage structure can potentially be altered by natural disturbance such as droughts, floods and violent storms (Van Vrancken & O'Connell, 2010). For example van Vrancken and O'Connell (2010) found that there were significant changes in fish assemblages at the downstream and upstream reaches of Bayou Lacombe stream in southeastern Louisiana after Hurricane Katrina in 2005. Their results revealed the differences in dissolved oxygen between pre-Katrina and post-Katrina were related to fish community changes in upstream reaches, while downstream stream changes in fish assemblage were associated with salinity and temperature (Van Vrancken & O'Connell, 2010).

1.7.5 Physical and chemical conditions The potential range that any given species can occupy is controlled by climatic conditions (Jackson et al., 2001), viz., physical conditions (e.g. temperature, hydrological regime), and chemical conditions (e.g. dissolved oxygen, pH, salinity). Elevated temperatures may result in high physiological demands and stress, as well as decreasing the oxygen saturation levels of water (Jackson et al., 2001). Sections of streams that are shallow and slow moving are prone to temperature elevation and decreased oxygen levels, owing to high decomposition and respiration rates, thus stressing fish present or favoring other species (Jackson et al., 2001). Often low oxygen levels develop due to high ambient temperatures and high respiration in tropical systems that have low flow rates or flood plain ponds (Jackson et al., 2001). Kramer (1983, cited in Jackson, et al., 2001) further adds that a greater degree of air breathing is exhibited in tropical

fishes compared to temperate fishes, which is possibly due to selective adaptation to low oxygen conditions (Jackson et al., 2001).

Differences in stream morphology affect flow dynamics at spatial and temporal scales, with consequent impacts on fish community structure (Jackson et al., 2001). The longitudinal position in stream fish assemblages has been shown to be related to water depth and substratum size for riffle and pool habitats (Gelwick, 1990). In Fiji, Boseto (2006) found that physical factors appear to determine species richness in variable environments at a local scale. He found that physical habitat factors such as temperature and river depth affected the total number of fish species and that distance from the coast for endemic species. Additionally, physical factors such as total area, total discharge and primary productivity along with historical factors such as speciation rates and dispersal are the chief determinants of species richness and control the importance of local scale factors (Lamouroux et al., 2002; Mathews, 1998).

1.8 The framework of ecological guilds Depending on the goals of the study, attributes to be emphasized, and the degree of quantitative analysis employed, fish communities are described or classified in different ways (Jackson et al., 2001). One method is the designation of species to groupings or guilds, each of which denotes certain attributes; this is where more recent studies have focused on this functional analysis of community structure (Elliott et al., 2007). Root (1967 cited in Elliott et al., 2007) defined “a guild as a group of species that exploit the same class of environmental resources in a similar way”. Hence, on the basis of many different life history traits, species can be grouped into guilds, viz, feeding guilds, flow preference guilds, and reproductive guilds (Aarts & Nienhuis, 2003). Moreover, due to its functional nature, this approach is convenient and useful, as it focuses on specific ecological attributes of the species (Jackson et al., 2001). Many authors have devised their own classification system, such as grouping fish species according to their feeding ecology (Aarts & Nienhuis, 2003). A study in Fiji by Jenkins & Mailautoka (2010) on the fishes of Nadi basin and bay, designated 13 distinct feeding guilds for the fishes within the study area, using feeding classification system used in Jenkins et al. (2010).

1.9 Aims and structure of this thesis The overarching goal of this study is to develop a better understanding of the parameters that affect the structure and functions of freshwater fish assemblages in Fiji, particularly looking into wadeable streams. A number of studies were carried out to quantitatively describe these parameters.

This research has the following aims: 1. To provide quantitative data on the distribution, species richness, and habitats, of fishes in wadeable streams of Nakorotobu and 2. Provide recommendations to assist management of freshwater ichthyofauna in an ecosystem based management (EBM) context.

The following research objectives will help achieve these aims: 1. To conduct a baseline survey on the freshwater fish assemblage to determine within stream zonation of individual species. 2. To compare the presence/absence and species diversity across two distinct tropical seasons; the wet season (February) and dry season (August). 3. To determine if there is any correlation of water quality data with the fish abundance and species richness. 4. To determine if there is any relationship between the fish assemblages with habitat and micro-habitat data.

Chapter 2 Study region

2.1 Location The Fiji archipelago is located in the Pacific Ocean between latitudes 16°-20° S and longitudes 178° E-178° W and consists of 332 islands of which about a third are inhabited; with 1.3 million km2 of oceanic Exclusive Economic Zone (EEZ) (Fiji Bureau of Statistics, 2010; Neall & Trewick, 2008; Parham, 1972). The two largest islands are Viti Levu (10,388 km²) and Vanua Levu (5,535 km²) (Neall & Trewick, 2008; Parham, 1972). The topography of Viti Levu and Vanua Levu is pronounced, with mountain heights between 900 and 1320 m above sea level. The study island Viti Levu consists of some 15% flat lands (varies little in elevation); these are mostly found along the coast, in the river valleys and flood plains of the four major river systems (Morrison & Clarke, 1990).

Its closeness to the Australian-Pacific plate boundary results in a complex geological history for Fiji (Neall & Trewick, 2008). Most islands are believed to be remnants of once active volcanoes sitting on a piece of the Pacific plate, drifting slowly southeast through an extensive zone of fracturing, volcanism and shearing (Mueller-Dombois & Fosberg, 1998). This is due to the subduction of the Pacific plate under the Australian plate (Mueller-Dombois & Fosberg, 1998). The oldest terrestrial areas of Fiji have probably been exposed for 5-20 million years whilst the youngest island, Taveuni, exhibited volcanic activity about 2000 years ago (Doyle & Fuller, 1998). The geological origin of Viti Levu began following convergence of a series of oceanic island-arc fragments (Nunn, 1994). Uplift of plutonic intrusions during the middle to late Miocene (412 Ma) formed its first significant land mass (Neall & Trewick, 2008), while continuing uplift of central Viti Levu occurred throughout the Quaternary (Nunn, 1994). Most soils are derived from volcanic material but some are comprised of uplifted marine reefs and sediments, and rivers on older islands have formed alluvial plains of sedimentary soils (Ash, 1992). Figure 2-1 shows the location of the study region on mainland Viti Levu.

Figure 2-1 The study region of Nakorotubu district, situated on the northern coast of the island of Viti Levu

2.2 Fiji’s climate The climate of Fiji is maritime tropical with no extremities of heat or cold. Fiji undergoes a distinct wet season (November-April) and a dry season which is mainly regulated by the north and south movement of the South Pacific Convergence Zone (SPCZ). Throughout all seasons the predominant winds are east to southeasterly trade winds which blow slightly stronger during the cool dry season (May-October) than during the warm wet season (November-April) (Fiji Meteorological Service, 2012). The island topography and the prevailing south-east trade winds influences rainfall in Fiji. The mountainous ranges of Viti Levu causes wet climatic zones on the windward side and dry climatic zones on the leeward side which results in pronounced dry and wet zones. However, little climatic differentiation occurs on the smaller island groups. Annual rainfall in the dry zones averages around 2000 mm while in the wet zones it ranges from 3000 mm around coastal areas to 6000 mm on mountainous sites (Fiji Meteorological Service, 2012).

2.3 Nakorotubu geology and geomorphology The study region falls on the northern section of Viti Levu and is approximately 80 km north of the capital, Suva. The northern part of Viti Levu consists of basaltic rocks that range in age from 5.5 to 3 Ma (Ollier & Terry, 1999). About 3200 km2 of northern Viti Levu is covered by Pliocene basaltic lava flows that include pillow lava and interbedded volcaniclastic rocks (McPhie, 1995).

A comprehensive overview on the volcanic geomorphology of northern Viti Levu is presented by Ollier and Terry (1999). In their paper they reveal the major drainage features and several volcanoes on northern Viti Levu. For the Nakorotubu range, the origin is unknown, however, due to it consisting largely of flow breccias, pyroclastics and volcanic conglomerates, it may therefore be almost entirely of submarine origin (Ollier & Terry, 1999). Its formation and uplift has consequences for the drainage of eastern Viti Levu (Ollier & Terry, 1999). In addition, streams on the coast of Nakorotubu (Bureiwai) are fairly short (~ 3 to 5 km long) and steep (pers. obs.).

Northern Viti Levu is an important volcanic area due to the fact that three major rivers, Ba, Sigatoka and Wainibuka River, originate from this area (Ollier & Terry, 1999). For instance, the Wainibuka River together with other tributaries of the Rewa River (Wainimala, Waidina and Waimanu Rivers) are responsible for draining nearly one third of the island of Viti Levu (Gehrke et al., 2011; Terry et al., 2002).

2.4 Nakorotubu climate The rainfall pattern is highly seasonal with average annual rainfall greater than 3,200 mm (Atherton et al., 2005). Particularly looking at average monthly rainfall patterns from the nearest Fiji Meteorological Station in Penang, Rakiraki reveals a total monthly rainfall of 591.8 mm in the wet season sampling of February. Rakiraki however is on the drier side of the island compared to Nakorotubu. Figure 2-2 shows the total monthly rainfall for the study region.

Figure 2-2 Total monthly rainfall taken from nearest Fiji Meteorological Station in Penang, Rakiraki. (Source: Fiji Meteorological Service, 2012).

2.5 Biodiversity and conservation work in the Nakorotubu range Biodiversity and conservation work in Nakorotubu is in its infancy. According to Bogiva (2008) the district of Nakorotubu covers an area of ~ 513 km2 stretching from Namatadamu village in Bureivanua, about two hours from Korovou town in wet Tailevu province to Nayavuira village. One of the largest tracts of forest in the country is found in the Nakorotubu mountain range, connecting crucial ecosystems and providing valuable services for the people of Nakorotubu (Bergen, 2010). Recently, the Fiji Water Foundation announced its support for the creation of a conservation area in the Nakauvadra and Nakorotubu range to build on the Viti Levu conservation corridor (Bergen, 2010).

2.5.1 Rapid assessment project In 2009, the University of the South Pacific-Institute of Applied Sciences (USP-IAS) together with partner organizations Conservation International (CI) led the first Rapid Assessment Project (RAP) in the interior of the Nakorotubu range (Bureivanua) which focused on the flora and

fauna and its relationships with the neighbouring watershed, the Nakauvadra range. A total of 556 confirmed species plants and animals were documented in the RAP expedition (Morrison et al., 2009). The RAP found several rare and endangered species such as the endemic palm Calamus vitiensis and the friendly ground dove, Gallicolumba kleinschmidti (Morrison et al., 2009). Interesting finds for aquatic resources included the endemic shrimp Caridina fijiana found at 570 m elevation (Lai et al., 2009); and the recently described goby Glossogobius illimis (Hoese & Allen, 2011) which was identified as Glossogobius n. sp. in Boseto (2009). However, no terrestrial biological survey has been done on the lowland coastal rainforest and this research is the first for freshwater vertebrates in the coastal streams of Nakorotubu (Bureiwai).

2.5.2 Marine conservation efforts in Nakorotubu There are 25 villages in Nakorotubu district with over 2000 residents. The marine iqoliqoli is believed to be one of Fiji’s most highly exploited (Bogiva, 2008). This is primarily due to its location within the Bligh waters, which is the hub for maritime voyage between Viti Levu and Vanua Levu and the numerous fishing vessels that fish within these waters (Bogiva, 2008). The Vatu-i-ra Passage, one of Fiji’s busiest sea passages, also occurs within the Nakorotubu iqoliqoli (Bogiva, 2008). The groundwork for marine conservation work in Nakorotubu began in 2005, which was organized by USP-IAS in the village of Namarai. A biological survey on two reefs in Nakorotubu in 2006 found that although coral life seemed healthy, fish stocks were average (Bogiva, 2008). This led to the declaration of 10 coral reefs as Marine Protected Areas (MPAs) in 2007, and this was further solidified by the reef-to-ridge concept where chiefs in the interior highlands of Nakorotubu have given their support to their coastal kinsmen (Bogiva, 2008).

2.5.3 Watershed management in Nakorotubu Implemented by IAS-USP in Fiji is the COWRIE project - Towards Coastal and Watershed Restoration for the Integrity of Island Environments. It aims to empower communities in Fiji to undertake management decisions towards the protection and restoration of their watersheds with specific links towards coral reef management (Koroiwaqa, 2010). The COWRIE project was funded by the Coral Reef Initiatives for the Pacific (CRISP) and administered by Conservation International (Koroiwaqa, 2010). The first phase of the project ended in 2010 where

demonstration plots of replanting a mix of exotic and native trees on ten hectares each across three villages in the district of Naroko (International Union for the Conservation of Nature, 2010). At the second site in Nakorotubu district, awareness and management planning workshops were undertaken using the Locally Managed Marine Areas participatory approach (International Union for the Conservation of Nature, 2010). Coastal and inland nurseries have been set up in strategic locations for seedling supplies in Nakorotubu and it is hoped that further funding will be provided for planting in 2012 (International Union for the Conservation of Nature, 2010).

Chapter 3 Methodology

3.1 Biological study Before the commencement of the study, the catchment areas along the coast of the Nakorotubu range (Bureiwai) were demarcated. Three catchments were then chosen for the research. Vucinivola was the largest at 4.61 km2 followed by Taveu and Nakawaqa at 3.34 and 1.32 km2 respectively (Figure 3-1). The three villages Nabukadra, Saioko and Naocabau were then visited where traditional protocols (sevusevu) were followed and consultation commenced with village headmen on the objectives of the research. Upon completion of the fieldwork an itautau was presented to the villagers.

Figure 3-1 Sampling stations (n=80) in wet and dry season survey.

3.1.1 Stream characterization Streams were categorized into three sections according to Fitzsimons et al. (2007) and Jenkins (2009b). a. Lower reach – section of the stream from ocean to first major barrier/obstacle (waterfall, culvert and/or weir)

b. Mid reach – moderately steep section characterized by formation of riffles and pools.

c. Upper reach – steep head water section with development of waterfalls and plunge pools.

3.1.2 Data collection In-stream habitat measurements, fish species richness and abundance were collected twice; in the wet season of February, 2011 and the dry season of August, 2011. Sampling lasted approximately six days per sampling occasion. Figure 3-2 illustrates the experimental design for each sampling occasion.

Figure 3-2 Experimental design of study carried out in Nakorotubu for wet and dry season sampling. Note that there should have been 90 stations; however, Nakawaqa mid and upper reach had dried up in the dry season and as a result there was a total of 80 stations. 5R = 5 replicate stations.

Nakorotubu

Taveu Vucinivola Nakawaqa

Lower Mid Upper Lower Mid Upper Lower Mid Upper

5R 5R 5R 5R 5R 5R 5R 5R 5R

3.1.3 Habitat sampling strategy A standardized methodology was employed in all surveys. For each 25 m reach, prior to anyone setting foot in the stream, water quality information was gathered using a commercial water quality meter (Horiba U50). Parameters recorded were dissolved oxygen (mg/L), temperature (°C), conductivity (μS/cm), acidity (pH) and turbidity (NTU). Position and altitude were taken using a Garmin 67Cx model Global Positioning System.

The upstream and downstream end of the 25 m section was then cordoned off with beach seine nets to prevent any fish from escaping or entering. A transect was laid across the stream within the 25m reach, at five meter intervals. At each transect, wetted width was measured using a fiber glass measuring tape. A quadrat (0.25 m × 0.25 m) was dropped randomly five times along this

transect. Within this quadrat, substrate type was recorded based on the classification of mineral substrates by particle size, according to the Wentworth Scale (Higashi & Nishimoto, 2007). This was further modified to suit the purpose of this study (see Table 3-1). Depth measurements were taken inside the quadrat using a stainless steel one meter ruler. At the midpoint of each transect two measurements were taken; canopy cover was visually estimated, and water velocity was taken at one tenth the maximum depth using a flowatch. Figure 3-3 depicts the in-stream habitat protocol for each station.

From the data, an approximation of the volume of water in the 25 m reach using the formula, length (25 m) × average wetted width × average depth, was computed. In addition, the average velocity in the stream (sum of the five velocity readings per station divided by five) and the average canopy cover over each station was calculated (sum of the five visual estimations taken in center of the stream divided by five).

Table 3-1 Substrate classification for in-stream habitat measurements modified according to the Wentworth Scale. Size Category Reference

Bedrock Solid continuous rock Boulder Head-size and larger Cobble Larger than fist, smaller than head size Gravel Fist size Pebble Thumbnail size Sand Sand-size Silt Smaller than pin head size

Figure 3-3 In-stream sampling protocol. Note that yellow boxes indicate quadrat where substrate and depth readings are taken. Furthermore, although not shown in the diagram, the upstream and downstream end would be blocked with beach seine nets.

3.1.4 Fish sampling Freshwater fish sampling techniques used are adapted from Jenkins (2009b) which is refined from sampling procedures described by Parham (2005) and Fitzsimons et al. (2007). These methods are intended to provide a detailed documentation of stream fishes in high tropical oceanic islands that are present in a range of in-stream habitats.

Sampling within the 25 m section lasted for approximately fifteen minutes. An electrofisher Smith-Root (500 V, 10 A) backpack unit was used together with beach seine nets (1 mm squared mesh size). The electrofisher was the primary sampling tool used as an efficient means of capturing unharmed fish at each 25 m section.

Electrofishing began at the downstream end of the 25 m section, with two field assistant holding the beach seine net downstream from the electrofisher (Figure 3-4). In between pulses the beach

seine net was examined for fishes. Stunned fish were also gathered using a small hand net (1 mm squared mesh size) and all fish collected were placed in a bucket. The electrofishing in conjunction with beach seine net continued until the upstream end was reached. In this way all river fauna was sampled.

Figure 3-4 Electrofishing in conjunction with a beach seine net. Notice the blockage nets set downstream in the background used to prevent fish from escaping or entering the 25 m reach.

3.2 Fish identification and preservation All fishes that could not be identified in-situ were taken back to the marine collection at the University of the South Pacific for further taxonomic work using available keys. Based on work conducted in Fiji by Mr. Aaron Jenkins, Mr. David Boseto and Mr. Kini Koto Mailautoka, the researchers have managed to compile a freshwater fish checklist (Boseto & Jenkins, 2006); and have developed a freshwater index guide for Fiji’s stream fishes. This was used along with additional field guides for the Oceania region in freshwater fish identification such as Allen (1991). The pipefish key by Dawson (1985) was used to key all pipefish collected. Voucher specimens were collected, fixed in 10% formalin for 5-10 days and transferred to 70% ethanol solution after fixation. This collection was then verified by ichthyologist Mr. Aaron Jenkins. Dr

Patricia Kailola helped in the identification of a worm eel (Moringua sp.) to the genus level. All these voucher specimens will be deposited into the USP Marine Collection.

3.3 Fish life history and feeding characteristics The life history classification follows that of Jenkins et al. (2010) which is slightly modified from that of Elliott et al. (2007). There were four life history classifications that were found for the stream ichthyofauna collected in this study; these were freshwater straggler (FS); amphidromy (A); obligate catadromy (COB) and facultative catadromy (FC). Seven feeding guilds were found for the fishes sampled in Nakorotubu. The feeding guild categories used were based on Jenkins & Mailautoka (2010) i.e. herbivore generalist (HG); invertivore specialist (IS); invertivore generalist (IG); insectivore generalist (InG); piscivore generalist (PG); carnivore (C); and generalist (G).

3.4 Data handling and analyses Fish abundance data, hydrological and water quality data were recorded for each station sampled in wet and dry season survey using Microsoft Excel (Microsoft Office 2007 suite). Data were transformed to presence/absence because the interest was in what species were present or absent not in the overall abundance of these species.

A modified gower, univariate permutational analysis of variance (with 9999 permutations) using dissimilarity matrices constructed with Euclidean distance were used to test for differences in the fish presence/absence transformed data, species diversity, hydrological and water quality using the PRIMER v.6 with PERMANOVA + add-on software (Anderson et al., 2008). This package was also used to calculate dissimilarity and diversity indices.

3.4.1 Fish community structure Jackobson dissimilarity was explored as a method for calculating dissimilarity between samples. Examination of the Sheppards plot constructed showed a large number of sites that had similarity equal to zero; meaning that large number of samples had no species in common. This was because relatively few species were recorded, and of the species present, some of them were very

rare occurring in only one or two (particularly mid and upper reach) sites. Euclidean distance was therefore used on the presence/absence data as the most suitable resemblance measure.

Formal tests were conducted using PERMANOVA + add on PRIMER 6 on the presence/absence based Euclidean distance dissimilarity matrices. Firstly, to determine if there was any significant difference of the term ‘station’ within the model, we used a model with the terms station nested in reach nested in stream. The results following 9999 permutations showed a permuted p-value of 0.9462 of the term station (reach (stream)) (d.f.=36, SS=9.1, unique permutations=9860) indicating no significant differences between stations within reaches within streams. Based on this result we removed the term station from all future models by combining data from the replicate stations.

To examine effects of season and reach within stream, we used a model with the following terms; season (fixed, 2 levels), reach (fixed, 3 levels nested in stream) and stream (fixed, 3 levels). We removed the term reach (stream) x season as there was only one measure at each reach within each stream at each season and interpreted the main effects.

3.4.2 Fish diversity The Shannon Wiener index was used to describe diversity observed within these data. The Shannon Wiener index was used as it is one of the most widely used traditional measures of diversity (Spellerberg & Fedor, 2003). Dummy variables were added to account for the large number of empty samples in which no species of fish were found.

Formal tests were conducted to compare Shannon Weiner diversity. Firstly, to determine if there was any significant difference of the term station within the model, we used a model with the terms station nested in reach nested in stream. The results following 9999 permutations showed a permuted p-value of 0.9562 of the term station (reach (stream)) (df.=36, SS=0..476, unique permutations=9925) indicating no significant differences between stations within reaches within streams. Based on this result we removed the term station from all future models by combining data from the replicate stations.

To examine effects of season and reach within stream on the Shannon Weiner diversity, we used a model with the following terms; season (fixed, 2 levels), reach (fixed, 3 levels nested in stream) and stream (fixed, 3 levels). We removed the term reach (stream) x season as there was only one measure at each reach within each stream at each season and examined the main effects

3.4.3 Stream hydrology and water quality Hydrological (stream depth, wetted width, velocity) and canopy cover data including water quality data were graphed using the GrapheR package (Hervé, 2011) in R statistical software (R Core Team, 2012). The substrate data was graphed using Microsoft Excel. A Shapiro-Wilk test showed that the substrate data were not normally distributed therefore ANOVA tests could not be performed. Hence, a Wilcoxon rank sum test was performed instead.

3.4.4 Fish environmental relationships Water quality Water quality data, abundance and species richness data were exported to JMP statistical software package (Ver. 5.0.1.2) on the Microsoft Windows 7 OS platform. A non-parametric Spearman rank correlation (Spearman, 1904) test was performed for total abundance and species richness at each station (n=80) against the water quality parameters at each station using the JMP package.

Habitat, micro-habitat and fish assemblages Data organization and entry were carried out using Microsoft Excel to organize the data for multivariate statistical analyses using CANOCO 4.5 (Ter Braak & Šmilauer, 2003) software. To analyze the data, species abundance and habitat data were first transformed into CANOCO format using the WCanoImp program (Ter Braak & Šmilauer, 2003). The ordination model and the permutation test in CANOCO were used to determine the statistical significance of the species-environment canonical relationship.

Multivariate analysis was used to investigate the relationship between the abundance of a particular species (response) and environmental variables (predictors). The examination of community composition may provide insights into complex ecological responses to disturbance

that are not easily made with univariate analyses (Leps & Šmilauer, 2003). The primary data (species data) consisted of the abundance of individual species (caught by electrofishing a cordoned 25 m section of wadeable stream). The individual sections (n=80) differed in their volume of water, altitude, water velocity and canopy cover. The data gathered represent fish and habitat sampling in the wet (February) and dry season (August) of 2011.

Firstly, the appropriate ordination model was selected (Leps & Šmilauer, 2003). Following the method of Leps & Šmilauer (2003), detrended correspondence analysis (DCA) was used to decide a priori for the method of ordination by estimating the heterogeneity in the species data using the length of the community composition gradients in species turnover units (Table 3-2).

Table 3-2 Length of gradient based on DCA, indirect gradient analysis. Axes 1 2 3 4 Total inertia Eigenvalues : 1 0.657 0.305 0.248 4.833 Lengths of gradient : 0 4.025 2.853 3.85 Species-environment correlations : 0.54 0.825 0.236 0.333 Cumulative percentage variance of species data : 20.7 34.3 40.6 45.7 of species-environment relation: 26.9 67.8 0 0

The largest value observed (the longest gradient) was 4.025. According to Leps & Šmilauer (2003) if the value is larger than 4.0, a unimodal method should be used; if less than 3.0 the linear method should be selected whilst for the range between 3 and 4, both types of ordination work reasonably well (Leps & Šmilauer, 2003). Unimodal methods (CCA, CA or DCA) work implicitly with standardized data, summarizing variation in the relative frequencies of the response variable (species) (Leps & Šmilauer, 2003). These methods cannot work with empty samples, i.e. records in which no species was present (Leps & Šmilauer, 2003). Due to this fact, the linear method was chosen for the analysis of species and environmental data collated across the three streams sampled. With an indirect analysis of the species data, PCA was used to summarize the community variation. For the species data, abundance was log transformed using log (y + 1) transformation to meet assumptions of normality. In building the model to quantify the effect of the environmental variables upon the fish assemblages, a redundancy analysis

(RDA) was performed in which all environmental variables were manually selected and tested during the forward selection of environmental variables. The following variables; altitude, volume and canopy cover had significant effects p<0.05 on the fish assemblages. The RDA was then carried out in which the following environmental variables velocity, wet and dry season were deleted from the analysis.

Chapter 4 Results

4.1 Electrofishing catch composition A total of 677 fish were caught over the wet and dry season electrofishing sampling. In the wet season survey a total of 376 fish were collected (representing 17 species) compared with 301 fish in the dry season (representing 22 species). A detailed checklist of the freshwater ichthyofauna found in the three streams surveyed after further taxonomy work was generated (Table 4-1). A total of 27 species were collected; these include a possible new genus and new species of pipefish, as well as an undescribed goby Stenogobius n sp. and two endemic gobies Schismatogobius vitiensis and Redigobius leveri. For statistical analyses, a total of 24 fish species were identified, which included the one genus-based category (Syngnathidae: Microphis spp.) that was used when in-situ species level determination was not possible.

Combining the wet and dry season data, the gudgeon Eleotris fusca was the most abundant (228 individuals) representing 34% of the total fish caught. Other relatively abundant species were the flagtails Kuhlia marginata (54 individuals, 8%) and K. rupestris (44 individuals, 6%); the giant marbled eel Anguilla marmorata (47 individuals, 7%); the gudgeon E. melanosoma (55 individuals, 8%) and the ornate goby Sicyopus zosterophorum (56 individuals, 8%). Of the 19 remaining individual species, each species composed less than 2 % of the total catch across the three streams. The abundance of the 24 species of fish grouped across the three streams surveyed in wet and dry season sampling is plotted in Figure 4-1.

Figure 4-1 Total abundance of each fish species caught in the wet and dry season, pooled across the three streams surveyed. 120

Dry

100

Wet

40 Total abundance of individual species species individual of abundance Total

Species

Table 4-1 Checklist of fishes in the three streams surveyed. Species are presented according to the phylogenetic order by family following Eschmeyer (2012); with species listed alphabetically. x indicates presence of species in that section of the stream. Vucinivola Vucinivola Vucinivola Taveu Taveu Taveu Nakawaqa Nakawaqa Nakawaqa Family Species lower mid upper lower mid upper lower mid uppers Anguilla marmorata Quoy & Gaimard 1824 x x Anguilla obscura Anguillidae Gunther, 1872 x Anguilla megastoma Kaup 1856 x Moringuidae Moringua sp. x x Gymnothorax polyuranodon Muraenidae (Bleeker 1853) x Microphis brachyurus (Bleeker 1853) x Microphis leiapsis Syngnathidae (Bleeker 1853) x Microphis retzi (Bleeker 1856) x x Cf. New genus new species x Ambassidae Ambassis miops Gunther 1872 x x x Kuhlia marginata (Cuvier, in Cuvier and Valenciennes 1829) x x x x Kuhliidae Kuhlia munda (de Vis 1884) x Kuhlia rupestris (Lacepède 1803) x x x x Lutjanus argentimaculatus Lutjanidae (Forsskål 1775) x Butis amboinensis Bleeker 1983 x Eleotridae Eleotris fusca (Forster, in Bloch and Schneider 1801) x x x x

Vucinivola Vucinivola Vucinivola Taveu Taveu Taveu Nakawaqa Nakawaqa Nakawaqa Family Species lower mid upper lower mid upper lower mid uppers Eleotris melanosoma Bleeker 1852 x x Giuris margaritacea (Valenciennces, in Cuvier & Valenciennes, 1837) x x x Hypseleotris guentheri (Bleeker, 1875) x x Awaous guamensis Valenciennes, in Cuvier & Valenciennes, 1837 x Glossogobius illimis Hoese & Allen, 2011 x Redigobius leveri (Fowler 1943) x x x Schismatogobius vitiensis Gobiidae Jenkins & Boseto, 2005 x x Sicyopterus lagocephalus (Commerson, in Lacepe`de, 1800) x x x x Sicyopus zosterophorum (Bleeker. 1856-57) x x x Stenogobius n. sp. x x Stiphodon rutilaureus Watson, 1996 x

4.2 Life history and feeding guilds All species sampled had some facet of their life-cycle within the marine environment. About 44% of the riverine fish sampled (Figure 4-2) undergo a distinct amphidromous life-cycle (gobies and gudgeons), while 22% were freshwater stragglers (glass perchlets and pipefishes). The other two groups were catadromous species which have been sub-divided into obligate catadromy (15%) and facultative catadromy (15%). As discussed in Jenkins et al. (2010), research has shown that some anguillid populations (eels) have been found to stay within marine systems throughout their lives; hence, the three species of eels caught in this study were classified as facultative catadromy. There was only one freshwater resident (4%) the endemic goby, Redigobius leveri.

Figure 4-2 Nakorotubu streams ichthyofauna life history categories. Adapted from Jenkins & Mailautoka (2010) which follows the descriptions of Elliott et al. (2007): freshwater straggler (FS); amphidromy (A); obligate catadromy (COB) freshwater resident (FR) and facultative catadromy (FC).

COB 15% FS 22%

FR 4%

FC 15%

A 44%

Invertivore specialist and carnivores made up the most common (>50% total) of the feeding guild at 33% and 26% respectively for the fishes of Nakorotubu (Figure 4-3). Piscivore generalist and invertivore generalist together accounted for about a quarter (15% and 11% respectively) of all the fish species. Generalist feeding which includes invertivore generalist and insectivore generalist was least common and accounted for about 15% of the feeding guild categories. 37

Figure 4-3 Feeding guilds of the ichthyofauna sampled in Nakorotubu. Feeding guild classes were: herbivore generalist (HG); invertivore specialist (IS); invertivore generalist (IG); insectivore generalist (InG); piscivore generalist (PG); carnivore (C); and generalist (G). PG 14.81% IG InG 11.11% 3.70%

C HG 25.93% 3.70% Other 14.81%

G IS 7.41% 33.33%

4.3 Longitudinal distribution of freshwater fish in Nakorotubu Based on the broad habitat scale discussed earlier (see section 3.1.1), the 24 species caught during this study varied longitudinally across the reaches of the streams (Figure 4-4). A total of eleven species (46% of total catch) were confined to the lower reaches of the three streams surveyed. Three species (13%) were present in lower and mid reach stations. Two species (8%) were only found in mid to upper reaches (at higher altitudes); these were Sicyopus zosterophorum and Anguilla obscura. One species (4%) Gymnothorax polyuranodon was only found in the mid reaches. A single species (4%) was found only in the lower reach and upper reach but not in the mid reaches, the goby Stiphodon rutilaureus. Finally, there were six species (25%) that were ubiquitous across the three reaches (i.e. Eleotris fusca, E. melanosoma, Kuhlia rupestris, Anguilla marmorata, Redigobius leveri and Sicyopterus lagocephalus.).

Figure 4-4 Longitudinal distribution of stream fishes from lower reaches to headwaters (n=80). 100%

90%

80%

70%

60% species across reach 50%

40%

30%

20%

10% Percentage of individual 0%

Species Lower Mid Upper

4.4 Exploratory analysis A multi-dimensional scaling plot (MDS plot) was constructed from the Euclidean distance dissimilarity matrix based on presence/absence transformed data (Figure 4-5). The MDS plot showed that lower reach sites are distinct from mid and upper reach sites (with the exception of Nakawaqa dry), but and that the lower reach wet season sites are similar to each other, but lower reach dry sites are unique and not similar to each other. Sites with similar habitat types (i.e. altitude, topography, hydrological regime etc.) showed greatest similarity in their faunal composition.

Figure 4-5 Multi-dimensional scaling plot of the presence/absence of species within reaches of each stream surveyed across wet and dry season. Sites represented by letters; V=Vucinivola; T=Taveu; N=Nakawaqa. Transform: Presence/absence Resemblance: D1 Euclidean distance NWetNWet 2D Stress: 0.07 Reach NDry Lower VDry Mid TDryTWet TWetTDry VDry Upper VDry Distance 2 2.7 VWet

VWet NWet TWet

VWet

TDry

4.5 Fish community structure analyses There were significant differences on the presence absence data for the effects of season and reach within a stream, especially for the term Reach(St) in the model (Table 4-2). A significant effect was also found for the interaction of stream and season (Table 4-2).

Table 4-2 PERMANOVA results on the presence absence data examining the effects of season and reach within stream. Significant values in bold. Source df SS MS Pseudo-F P(perm) perms Stream 2 17.514 8.7571 5.5002 0.0001 9877 Season 1 4.0733 4.0733 2.5584 0.0018 9933 Reach(St) 6 43.067 7.1778 4.5082 0.0001 9852 StxSe 2 5.0762 2.5381 1.5941 0.0271 9907 Residual 68 108.27 1.5922 Total 79 179.51

Finally, to examine the effect of reach on community structure, we undertook pair-wise tests on the term reach nested within stream. Having shown that for Nakawaqa there was a significant effect of season (Table 4-3) and for other streams there was some indication of an effect. Pair- wise tests of the reach within stream were conducted on wet and dry season samples separately. Monte-Carlo tests were done as the maximum numbers of permutations under the model were low based on the low degrees of freedom in the pair-wise comparisons (Table 4-3). Pair wise test showed significant differences with certain reaches of each stream (Taveu, Nakawaqa and Vucinivola) for both seasons (Table 4-4).

Table 4-3 PERMANOVA pairwise tests for the effect of season on community structure. Significant values in bold. Groups t P(perm) Unique perms

Nakawaqa Dry, Wet 1.7889 0.0024 8359 Taveu Dry, Wet 1.296 0.0714 9786

Vucinivola Dry, Wet 1.2344 0.0935 9799

Table 4-4 PERMANOVA pair-wise tests of the effect of reach within stream conducted in wet and dry season on fish presence/absence. Significant values in bold. P (perm) was p-value based on n where n = unique permutations. P(MC) was p-value based on Carlo test. Groups T P(perm) Unique perms P(MC) Wet Season Nakawaqa Lower, Mid 2.0702 0.0065 14 0.0184 Lower, Upper 2.3664 0.0074 12 0.0082 Mid, Upper 0.75593 1 2 0.5331 Taveu

Lower, Mid 2.0301 0.0072 12 0.0126 Lower, Upper 1.9685 0.0075 11 0.0152 Mid, Upper 0.5547 1 6 0.7894 Vucinivola

Lower, Mid 1.3031 0.077 13 0.1372 Lower, Upper 1.9224 0.0067 15 0.0107 Mid, Upper 1.633 0.0093 11 0.0346 Dry Season

Taveu

Lower, Mid 2.1752 0.0078 15 0.0061 Lower, Upper 2.0506 0.0071 13 0.0115 Mid, Upper 1.3628 0.2072 8 0.1699 Vucinivola

Lower, Mid 1.2688 0.1172 10 0.1739 Lower, Upper 2.0131 0.0084 16 0.0106 Mid, Upper 1.587 0.0318 10 0.0512

4.6 Fish species diversity index Shannon Wiener diversity index analysis showed that lower reach sites during wet and dry seasons had the highest diversity on average, ranging from 1.2-1.8 (Figure 4-6). A decline was observed at mid to upper reaches, with values for these sites sampled ranging between 1-1.6. Further explanation on this difference is found section 4.7, where PERMANOVA and pairwise comparison were undertaken.

Figure 4-6 Shannon Wiener diversity index for the three streams measured across wet and dry season.

Nakawaqa stream Taveu stream Vucinivola stream

Dry Dry Dry Wet Wet Wet Shannon Weiner indexShannon Weiner Shannon Weiner indexShannon Weiner Shannon Weiner indexShannon Weiner 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 Lower Mid Upper Lower Mid Upper Lower Mid Upper

Reach Reach Reach

4.7 Shannon Wiener diversity analyses PERMANOVA results showed only significant differences for the model Reach(St) (Table 4-5). Finally, to examine the effect of reach on Shannon Weiner diversity, we undertook pair-wise tests on the term reach nested within stream. Pair-wise tests of the reach within stream were conducted on the three streams separately. Monte-Carlo tests were done as the maximum numbers of permutations under the model were low based on the low degrees of freedom in the pair-wise comparisons (Table 4-6). Pair-wise test showed only some reaches are significantly different from each other (Table 4-6).

Table 4-5 PERMANOVA results on the Shannon Weiner diversity data examining the effects of season and reach within stream. Significant values are in bold. Source df SS MS Pseudo-F P(perm) Unique perms Stream 2 2.56E-02 1.28E-02 0.73333 0.4823 9945 Season 1 3.85E-02 3.85E-02 2.2035 0.1436 9836 Reach(St) 6 0.37728 6.29E-02 3.5984 0.004 9942 StxSe 2 6.53E-02 3.26E-02 1.868 0.1619 9957 Residual 68 1.1883 1.75E-02 Total 79 1.963

Table 4-6 PERMANOVA pair-wise test on the effect of reach within a stream on Shannon Weiner diversity. Significant values are in bold. P (perm) is p-value based on n where n = unique permutations. P(MC) is p-value based on Carlo test. t P(perm) Unique perms P(MC) Nakawaqa groups Lower, Mid 2.9322 0.0135 8204 0.0123 Lower, Upper 3.5884 0.0055 7547 0.0027 Mid, Upper 1 1 1 0.3478 Taveu groups Lower, Mid 0.23907 0.8203 9845 0.8148 Lower, Upper 2.5258 0.0213 9799 0.0233 Mid, Upper 1.9446 0.0727 9532 0.0676 Vucinivola groups Lower, Mid 0.43819 0.6844 9853 0.6622 Lower, Upper 1.3504 0.1938 9815 0.1938 Mid, Upper 1.2902 0.2232 9841 0.2109

4.8 Habitat and microhabitat data

4.8.1 Velocity, canopy cover, wetted width and stream depth Box plots of the velocity, canopy cover, wetted width and stream depth gathered for the three streams in wet and dry season sampling were used for comparative purposes (Figure 4-7). It shows the minimum, maximum and median values of the variables as well as the 25-75% values of which are lodged in the box. Extreme values of each parameter measured are shown as outliers. Overall there was a general decrease in velocity, canopy cover, wetted width and stream across the three streams during the dry season. A PERMANOVA pair-wise test on the differences across season showed only significant differences for stream depth in Taveu lower (t=4.3643, P(perm)=0.0087) and Taveu mid (t=2.3196, P(perm)=0.0161).

Figure 4-7 Box and whisker plots showing median differences in stream velocity, canopy cover, wetted width and stream depth sampled across reach and season. Note that there were no measurements for mid and upper Nakawaqa in the dry season due to this sections drying up. The symbol * denotes a significant difference within each reach across season (p<0.05). Nakawaqa Taveu Vucinivola

Dry Dry Dry Wet Wet Wet ) s / m ( Velocity (m/s) Velocity (m/s) Velocity 0 20406080100 0 20406080100 0 20406080100 Lower Mid Upper Lower Mid Upper Lower Mid Upper

Nakawaqa Taveu Vucinivola

Dry Dry Dry Wet Wet Wet (%) (%) anopy cover cover anopy anopy cover cover anopy Canopy cover (%) Canopy cover C C 0 20406080100 0 20406080100 0 20406080100

Lower Mid Upper Lower Mid Upper Lower Mid Upper

Nakawaqa Taveu Vucinivola

Dry Dry Dry Wet Wet Wet Wetted width(m) Wetted width(m) Wetted width(m) 0 5 10 15 20 0 5 10 15 20 0 5 10 15 20

Lower Mid Upper Lower Mid Upper Lower Mid Upper

Nakawaqa Taveu Vucinivola

Dry Dry Dry Wet Wet Wet * * Stream depth(m) Stream Stream depth(m) Stream Stream depth(m) Stream 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Lower Mid Upper Lower Mid Upper Lower Mid Upper

4.8.2 Substrate cover A Wilcoxon rank sum test on substrate cover did not show any significant difference between seasons (wet and dry). Overall there was very high cover of pebble, cobble, boulder and bedrock for all the streams surveyed (Figure 4-8, Figure 4-9 and Figure 4-10). For Vucinivola stream gravel, pebble, cobble and boulder recorded the highest percentage cover in the lower and mid reach. The upper reaches of Vucinivola stream were dominated by bedrock. A similar substrate cover was also found in Taveu stream from the lower reaches to headwaters. For Nakawaqa silt was more prevalent compared to the two other streams in the lower reaches but cobble and boulder were the dominant cover for the lower reach. For mid and upper Nakawaqa the stream was characterized by a dominant bedrock cover. Note that no substrate readings were taken for mid and upper Nakawaqa due to the drying up of these sections of the stream.

Figure 4-8 Mean substrate cover in Vucinivola stream (mean ± S.E). 14 Mean wet

12 Mean Dry

4 Mean occurrence Mean occurrence

0 Silt Silt Silt Sand Sand Sand Gravel Gravel Gravel Pebble Pebble Pebble Cobble Cobble Cobble Boulder Boulder Boulder Bed rock Bed rock Bed rock Vucinivola lower Vucinivola mid Vucinivola upper Stream and reach

Figure 4-9 Mean substrate cover in Taveu stream (mean ± S.E). 14 Mean wet

12 Mean Dry

Mean occurrence Mean occurrence 4

0 Silt Silt Silt Sand Sand Sand Gravel Gravel Gravel Pebble Pebble Pebble Cobble Cobble Cobble Boulder Boulder Boulder Bed rock Bed rock Bed rock Taveu lower Taveu mid Taveu upper

Stream and reach

Figure 4-10 Mean substrate cover in Nakawaqa stream (mean ± S.E). Note that there was no measurement for mid and upper Nakawaqa in the dry season due to this sections drying up. 14 Mean wet 12 Mean Dry 10

4 Mean occurrence

0 Silt Silt Silt Sand Sand Sand Gravel Gravel Gravel Pebble Pebble Pebble Cobble Cobble Cobble Boulder Boulder Boulder Bed rock Bed rock Bed rock Nakawaqa lower Nakawaqa mid Nakawaqa upper Stream and reach

4.8.3 Water quality parameters Box plots of the water quality gathered for the three streams in wet and dry season sampling were used for comparative purposes (Figure 4-11). It shows the minimum, maximum and median values of the variables as well as the 25-75% values of which are lodged in the box. Extreme values of each parameter measured are shown as outliers. Water qualities for the three streams varied across wet and dry season particularly for turbidity which was nearly double in the wet season sampling compared to the dry season. Nakawaqa upper wet season had the highest median turbidity across the three streams. Dissolved oxygen was slightly higher in the wet season with Vucinivola upper recording the highest reading at 10.16 mg/l. Temperature was higher in the dry season compared to wet season and pH values were fairly stable across both seasons. Conductivity readings were generally higher in lower reaches due to tidal influence.

A PERMANOVA pair-wise test on the differences in water quality across season showed only significant difference for dissolved oxygen in Nakawaqa lower ((t) 3.6814, P(perm) 0.004). Significant differences in temperature for Taveu lower ((t) 4.6605, P(perm) 0.006); Taveu upper ((t) 17.083, P(perm) 0.005); Vucinivola lower ((t) 2.4482, P(perm) 0.038); Vucinivola mid ((t) 6.5375, P(perm) 0.011). Significant differences for turbidity in Nakawaqa lower ((t) 3.5806, P(perm) 0.01); Taveu mid ((t) 14.006, P(perm) 0.009); upper ((t) 4.2625, P(perm) 0.009); Vucinivola upper (t) 4.5892, P(perm) 0.011). Finally for pH only in Taveu upper ((t) 4.291, P(perm) 0.0239) there was significant differences across season.

Figure 4-11 Box and whisker plots showing median differences in water quality parameters sampled across reach and season. Note that there were no measurements for mid and upper Nakawaqa in the dry season due to this sections drying up. The symbol * denotes a significant difference within each reach across season (p<0.05). Nakawaqa Taveu Vucinivola

Dissolved oxygen Dissolved oxygen Dissolved oxygen * Dissolved (mg/L) oxygen Dissolved (mg/L) oxygen Dissolved (mg/L) oxygen

Dry Dry Dry Wet Wet Wet 7.0 7.5 8.0 8.5 9.0 9.5 10.0 7.0 7.5 8.0 8.5 9.0 9.5 10.0 7.0 7.5 8.0 8.5 9.0 9.5 10.0

Lower Mid Upper Lower Mid Upper Lower Mid Upper

Nakawaqa Taveu Vucinivola

Conductivity Conductivity Conductivity Conductivity (μS/cm) Conductivity (μS/cm) Conductivity (μS/cm) Conductivity

Dry Dry Dry Wet Wet Wet 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.20

Lower Mid Upper Lower Mid Upper Lower Mid Upper

Temperature Temperature Temperature * * * * Temperature(°C) Temperature(°C) Temperature(°C)

Dry Dry Dry Wet

Wet Wet 23 24 25 26 27 23 24 25 26 27 23 24 25 26 27

Lower Mid Upper Lower Mid Upper Lower Mid Upper

Nakawaqa Taveu Vucinivola

Turbidity Turbidity Turbidity

Dry Dry Dry Wet Wet Wet

* * * * Turbidity (NTU) Turbidity Turbidity (NTU) Turbidity Turbidity (NTU) Turbidity * 0 5 10 15 20 0 5 10 15 20 0 5 10 15 20

Lower Mid Upper Lower Mid Upper Lower Mid Upper

pH pH pH

Dry Dry Dry Wet Wet Wet

* pH pH pH 5678910 5678910 5678910 Lower Mid Upper Lower Mid Upper Lower Mid Upper

4.9 Ecological-environmental relationships

4.9.1 Water quality and fish community Water quality data were then correlated to the total abundance of fish per station; water quality and abundance data were not normally distributed hence a non-parametric Spearman’s Rho test was performed. The total abundance of fish was positively correlated (Table 4-7) with conductivity and was highly significant (Spearmen Rho=0.5694, p<0.001). Total abundance of fish was negatively correlated with turbidity and pH and both were significant (Spearmen Rho=-0.2727, p=0.0144; Spearmen Rho= - 0.2364, p=0.03477 respectively).

Table 4-7 Correlation summary table of environmental parameters versus abundance of fish per station. Variable by Variable Spearman Rho Prob>|Rho|

Dissolved oxygen Abundance of fish per station -0.0498 0.6607 Conductivity Abundance of fish per station 0.5694 <.0001 Temperature Abundance of fish per station 0.1872 0.0963 Turbidity Abundance of fish per station -0.2727 0.0144 pH Abundance of fish per station -0.2364 0.0347

The same was also done for species richness per station correlated against the water quality data. The total species richness of fish per station was positively correlated (Table 4-8) with conductivity and was highly significant (Spearmen Rho=0.6374, p<0.001). Also the total species richness of fish per station was negatively correlated with turbidity and was significant (Spearmen Rho=-0.2372, p=0.0341).

Table 4-8 Correlation summary table of environmental parameters versus fish species richness per station. Variable by Variable Spearman Rho Prob>|Rho| Species richness Dissolved oxygen (mg/l) -0.0300 0.7917 Species richness Conductivity (mS/cm) 0.6374 <.0001 Species richness Temperature (°C) 0.1211 0.2845 Species richness Turbidity (NTU) -0.2372 0.0341 Species richness pH -0.1074 0.3430

4.9.2 Habitat, micro-habitat data and fish assemblage The first two PCA axes (principal components) explain 48% (0.359 + 0.122) of the variability in species data. Up to 25.3% (0.253) of the variability in fish assemblage composition is explainable using the environmental variables (Table 4-9).

Table 4-9 Summary table of PCA output in CANOCO (indirect gradient analysis). Axes 1 2 3 4 Total variance

Eigenvalues : Species-environment correlations : 0.359 0.122 0.095 0.089 Cumulative percentage variance 0.746 0.356 0.246 0.411 of species data : 35.9 48.1 57.6 66.5 of species-environment relation: 78.9 85 87.3 93.2 1 Sum of all eigenvalues 1 Sum of all canonical eigenvalues 0.253

The result of the PCA analysis was illustrated using the biplot diagram (Figure 4-12). The first principal component is correlated mainly with volume (increasing from left to the right side of the diagram) and with the relative importance of altitude increasing in the opposite direction. Species such as Kuhlia rupestris, Eleotris fusca and Giuris margaritacea tended to be found more frequently or in higher abundance in sections of streams with greater volume of water. The goby, Sicyopus zosterophorum, were found at higher altitude (mid-upper reaches) and in greater abundance; hence their arrows point in similar direction as altitude.

Figure 4-12 Species-environment biplot diagram from the PCA with environment variables passively projected into the resulting ordination space.

The canonical axis (axis 1) explained 20% of the total variability in the species data (refer to Table 4-10). The significance of the three environmental variables on the variation of stream fish assemblages was assessed using Monte Carlo permutations test (9999 permutations under full model) and was confirmed as highly significant (p=0.0001).

Table 4-10 Summary table of RDA in CANOCO (direct gradient analysis). Axes 1 2 3 4 Total variance Eigenvalues : 0.2 0.016 0.003 0.182 1 Species-environment correlations : 0.759 0.45 0.303 0 Cumulative percentage variance of species data : 20 21.6 22 40.2 of species-environment relation: 91.2 98.5 100 0 Sum of all eigenvalues 1 Sum of all canonical eigenvalues 0.22

Summary of Monte Carlo test Test of significance of all canonical axes: Trace = 0.220 F-ratio = 7.137 P-value = 0.0001 (9999 permutations under full model)

Only species that had their abundance well explained by the first axis were displayed in this biplot diagram. Since the first RDA axis explained 20% of variability in species data, this was set as the threshold in the CanoDraw program (Ter Braak & Šmilauer, 2003) and only four fish species pass this criterion, i.e. Eleotris fusca, Kuhlia rupestris, K. marginata, and Anguilla obscura (Figure 4-13).

Figure 4-13 Species-environment biplot from the RDA summarizing differences in fish assemblages along the three environmental variables.

Chapter 5 General Discussion The overall objective of this thesis was to determine the various environmental factors affecting fish assemblages in wadeable streams of Nakorotubu. The results of this study showed that position in catchment, volume of water and canopy cover were the main factors influencing freshwater fish community structure in wadeable streams of Nakorotubu. The findings corroborate a longstanding global notion of maintaining natural flow regimes for the conservation of aquatic fauna and flora.

5.1 Spatial variation in fish assemblages Selections of habitats to live in are important ecological processes that determine the distribution of animal in space and time. Fish assemblages varied spatial and temporally across the three streams surveyed which reflects the broad changes in habitat types longitudinally within the catchment and the temporal shifts of habitat and micro-habitats in wet and dry season sampling; changes in volume of water, water velocity, canopy cover and water quality.

The study clearly shows the longitudinal habitat preferences of fish in wadeable streams of Fiji. The fish species colonising the three streams are distributed along the river from the lower reaches of freshwater to the headwaters according to their ecology. Some are therefore found at a certain altitude according to the physiochemical parameters and its hydrological properties. For instance, the amphidromous goby, Sicyopus zosterophorum spends the early phases of their lifecycle out at sea and colonize rivers and streams at the onset of physical and chemical cues. In essence, Baker (1978) defined migration as the act of moving from one spatial unit to another. For S. zosterophorum, this ecological migration will entail movement across lower reaches to colonize mid and upper reaches. Compared to other species of gobies found in the study, S. zosterophorum was only found in mid to upper reach sites. Presumably this mid to upper habitat reach preference by S. zosterophorum as an adult could be used as a means of evading the carnivorous flagtails Kuhlia rupestris and K. marginata that are not morphologically adapted to surmount barriers such as waterfalls.

The same was clear for Macrobrachium lar (freshwater prawns) which were more abundant in headwaters where Kuhlia were not found. For example, a survey of stream fishes in Palau found that the small gobies increased in abundance and freshwater prawns became more abundant at sites without Kuhlia rupestris (Nelson et al., 1995). It is also possible that S. zosterophorum is more rheophilic (preferring to live in fast flowing currents) in nature when compared to the other gobies found in the survey. In general, water velocity is faster in mid and upper reaches and this slowly wanes towards the lower reaches. However, this difference in velocity from headwater to lower reaches was not clearly evident across the three streams surveyed.

The two gobies, Sicyopterus lagocephalus and Redigobius leveri, were ubiquitous across the reaches and were more abundant in lower reach sites and usually found in shallow habitats with fine sand, gravel, pebble and cobble substrate. Species such as Kuhlia rupestris, K. marginata, Giuris margaritacea and Anguilla marmorata were more common in deeper and wider sections of the stream with greater cover of cobble and boulder. The gudgeons Eleotris fusca and E. melanosoma were primarily found on the edges of stream that had a high cover of overhanging vegetation and root masses.

E. fusca was present from lower reaches to headwaters, however, it was only found in the headwaters of Vucinivola stream. Because lower and mid sections of Vucinivola stream had no natural barriers such as waterfalls compared to Taveu stream which had a waterfall in the lower reaches and therefore had no gudgeons in the mid and upper reaches. Another likely reason for the absence of E. fusca in the lower reaches of the Vucinivola catchment is that it has shallower slopes compared with Taveu and Nakawaqa catchments. These results echo those of Jenkins & Jupiter (2011) who found that species that are typically found in lower to mid reach areas can extend to upper catchments when slopes are low and there are no barriers to dispersal.

A study by Jupiter et al. (2012) in Vanua Levu found extremely low species richness in upstream sites with good catchment and forest riparian cover when there were overhanging culverts present downstream. Fortunately the culverts that were present in

lower Vucinivola and Taveu stream were not overhanging and allowed direct passage for upstream and downstream migration of aquatic fauna. There is considerable amount of research documenting the impacts of human activities on riverine connectivity and many of these impacts have complex and interrelated cumulative effects (Pringle, 2001). Studies in the Oceania region have shown that even in small streams, physical barriers such as road crossings (e.g. Jenkins et al., 2010), small dams (e.g. Jenkins & Mailautoka, 2010), small impoundments (e.g Brainwood et al., 2008) have drastic impacts on riverine assemblages.

Nakawaqa stream had a considerably different fish assemblage in the mid and upper reaches compared to the other two streams. This was clearly shown in the MDS ordination, where Nakawaqa mid and upper reach having no similarity to the other two streams. The eel Anguilla obscura and the monkey river prawn Macrobrachium lar were the only species present in the mid and upper reaches of Nakawaqa stream in the wet season and was assumed absent because the stream was dry. Amphidromous species such as gobies and gudgeons that were present in the mid and upper section of the other two streams were absent in Nakawaqa mid and upper reach. This could be due to the fact that the headwaters of Nakawaqa stream had been split in half by the main road that runs through the coastal district of Nakorotubu, compared with the other two streams where the road passes through the lower reaches of each stream. As a result of this, turbidity readings were higher in Nakawaqa stream compared to the other two streams. Road crossings across streams not only cause physical barriers but also act as a focal point for the entry of sediments (Jenkins et al., 2010).

Habitat mobility was very high with a majority of the fish species moving across different spatial units in their lifespan especially the diadromous species that spend their larval and post-larval stage in the marine environment. About 37% of the species traverse the salt water medium into the terminal reaches of streams and then settle at the lower, mid and headwater sections of the stream. These species have evolved morphological adaptations such as fused pelvic fins to attach to substratum and dorso-lateral flattening to enable surmounting of waterfalls (Jenkins et al., 2010; Keith, 2003).

Nearly half of the fish species (46%) were confined to lower reaches (lower limits of freshwater) due to their inability to surmount natural and/or manmade barriers. A total of 17% of the species sampled, spend their early life-stages in the marine environment and then settle in the lower and mid reaches of Nakorotubu. However, the range of some of these species could be extended to the headwaters, such as the freshwater moray Gymnothorax polyuranodon which was found in Vucinivola mid. G. polyuranodon has been documented in the headwaters of the Wainibuka River in the Nakauvadra range, a tributary of the Rewa River c. 90-100 km from the sea by Copeland & Mailautoka (unpubl. data). Other research carried out by Allen (unpubl. data in Ebner et al., 2011) reports that the adult phase of G. polyuranodon has been collected or observed in West Papua, Indonesia, Papua New Guinea and Solomon Islands exclusively in pure fresh water; well above the high tide mark and within c. 5-10 km of the sea.

Overall, lower reach sites had significantly higher species diversity and greater abundance; and this gradually decreased with increase in altitude. In general, position in catchment was a significant factor influencing the fish assemblages across the streams in Nakorotubu. A comparable study carried out in Vanua Levu by Jenkins & Jupiter (2011) found that species diversity, abundance and biomass, tends to increase moving from upstream to downstream. There is a large body of literature on the longitudinal decrease in species diversity and abundance with altitude and distance from the sea (Boseto, 2006; Boseto et al., 2007; Jenkins & Jupiter, 2011; Rayner et al., 2008). This longitudinal pattern in fish assemblages for tropical islands of the Pacific is different when compared to large continental landmasses which can have higher faunal diversity and greater numerical abundance for the upper catchment assemblages (Jenkins & Jupiter, 2011).

Generally, these studies show that the richness of the fauna increase downstream often with increases in diversity of aquatic habitats (Pusey et al., 1993, 1995; Rayner et al., 2008). Although this research focuses on wadeable coastal streams which are relatively short (4-6km) and steep; the longitudinal patterns identified by various studies in large

river systems (Boseto et al., 2007; Hyslop, 1998; Jenkins & Jupiter, 2011; Pusey et al., 1995; Russell et al., 2003) are also evident in the short coastal streams of Nakorotubu.

5.2 Seasonal shifts in fish assemblages The shift in fish community structure across wet and dry season was noticeable for the three streams sampled. About 63% of the species were observed in both seasons, whereas seven species (29%) were sampled only in the dry season. In contrast two species (8%) were only found in the wet season, Anguilla obscura and Glossogobius illimis. Despite these changes, the fish assemblages did not differ significantly across season. The causes of this seasonal exclusivity are likely due to a combination of sampling variability and species level preferences for particular seasonally available habitats and water characteristics (Jenkins & Jupiter, 2011). For example, since most gobiids do not possess a swim bladder and are negatively buoyant, individuals that are shocked will most likely not rise to the surface and in swift flowing streams the electro-shocked fish are quickly swept into rocky interstitial spaces (Thuesen et al., 2011). The seven species that were only observed in the dry season could have been present in the wet season; but due to water levels being too high, the electrofisher would most likely not catch these species. The endemic goby Schismatogobius vitiensis is known to hide within the interstitial spaces of rocky substrates and because waters levels dropped across the three streams in the dry season electrofishing was able to observe these species.

The eel Anguilla obscura sampled only in the wet season in Nakawaqa stream is likely taking advantage of the available habitats in mid and upper reaches and has presumably monopolized this mid to upper reach by being the only carnivorous species present that preys on the high number of Macrobrachium lar observed in this section of the stream. The habitat and micro-habitat attributes in Nakawaqa stream is better suited for A. obscura compared with the two close relatives A. marmorata and A. megastoma also found in this study. A. obscura may have higher preferences for decreased water velocity and higher turbidity compared to the other two species of eels. For example a survey in Samoa found that A. obscura was commonly found in swampy taro patch streams with little flow (Jenkins pers. comm., 2013). Mid and upper Nakawaqa stream was devoid of

gudgeons and gobies in the wet season and as a result due to the habitats and food sources that they presumably preferred were unavailable these species was not found in the dry season sampling.

Assessment of the catch composition for three streams in wet and dry season sampling reveals that Eleotris fusca dominated the catch composition in both seasons; however, it was higher in the wet compared to the dry season (120 vs. 108 individuals respectively). This was also true for E. melanosoma, Ambassis miops, Anguilla marmorata, Microphis spp. Hypseleotris guentheri and Stiphodon rutilaureus, which were present in both seasons but were more common in the wet. The greater abundance of these species may be due to the presence of increased amounts of habitable space, as suggested in Jenkins and Jupiter (2011). In this study, due to the inability to identify in-situ pipefishes to species level; it is possible that certain pipefish species recorded after further taxonomy work would have been more abundant in either season or exclusive to one season. For example, the single specimen collected which is a putative new genus and new species of pipefish (Family: Syngnathidae) from Vucinivola stream was only discovered in the dry season.

A single juvenile mangrove snapper Lutjanus argentimaculatus (<40 mm) was caught in the lower reaches of freshwater in Taveu stream in the dry season (August). Research has shown that juvenile L. argentimaculatus less than 50 mm have been sampled in Queensland Australia from the months of February to July, suggest a prolong recruitment into freshwater habitats (Russell & McDougall, 2005). This also imply that juvenile of this species could have been present in the wet season survey carried out in February but was not sampled by the electrofisher.

The findings of this study are indicative of these types of shifts in fish community structure. Overall, these changes in fish assemblages did not differ significantly across the three streams in wet and dry season. But at the catchment level species richness was significantly higher in Vucinivola stream compared to the other two streams. This higher richness could be owed to the fact that Vucinivola stream is the largest catchment of the

three. This equates to a greater extent of available habitats for fishes. This bigger catchment size favours massive freshwater flow into estuaries, thus allowing more different species of post-larvae from the sea to colonise Vucinivola stream. On the contrary a stream like Nakawaqa which is intermittent (cease flowing for weeks or months each year) due to its smaller catchment size and greater steepness, results in decreased fish abundance and species richness. In the wet tropics of Australia, species richness is linked to catchment size and flow variability; with large catchments and predictable flow regimes containing the greatest richness (Pusey & Kennard, 1996).

A study in the coastal wet tropics of Australia found that the largest catchments were more speciose (20 species) compared to the smallest catchment which had seven species (Thuesen et al., 2011). Furthermore, catchment cover plays an equally important role in determining fish assemblages. Research by Jenkins & Jupiter (2011) found that significant differences in wet season effects on total fish abundance and diversity is possibly related to strong differences in the land catchment cover between Macuata and Kubulau catchments (25,789 vs. 3,306 ha). Overall, these three small coastal streams in Nakorotubu are possibly ephemeral in their hydrology over geologic timescales and vulnerable to dewatering; as is the case for streams of high Indo-Pacific islands (Thuesen et al., 2011).

5.2.1 Spatial and temporal variation in habitats and micro-habitats Habitat complexity and availability have a crucial role in affecting the variation of fish assemblages over time. More importantly the major determinant of aquatic habitat structure is the hydrological regime which consequently affects riverine fish and invertebrate community composition (Benke, 2001; Bunn & Arthington, 2002). The study determined the spatial and temporal variability in habitat and micro-habitats across the reaches of three streams. Generally, the three streams sampled in this study represent a spatially heterogeneous and temporally dynamic habitat and assemblage structure.

Instream habitat formation is a dynamic process. As aforementioned, the catchment hydrology influences the instream distribution of substrate size and the stream velocity.

The extent of stream power during flooding events varies with the slope and shape of the stream therefore influencing instream habitats. River and streams in Fiji are dependent on highly seasonal rainfall between November and April. Moreover, Pacific island fluvial systems are highly dynamic compared to other regions due to the wet tropical climate that brings about frequent and intense tropical storms, steep topography, tectonic uplift and anthropogenic factors such as forest clearing (Terry et al., 2002).

For the three catchments the seasonal change in rainfall amount was clearly evident in Nakawaqa; with mid and upper sections completely drying up during the dry season sampling in August. Vucinivola and Taveu stream also recorded decreases in mean wetted width and mean depth during the dry season. Substrate cover was fairly uniform across the three streams; however, there was a noticeable difference as you move further upstream with larger boulders and bedrock increasing in mean occurrence. Overall there was no noticeable change over the wet and dry season substrate cover. This could be due to fact that there were no serious flooding events in between the sampling periods.

5.3 Fish assemblages and environmental factors

5.3.1 Water quality Fish community assemblages are influenced by water quality conditions. This study related the freshwater fish assemblages of Nakorotubu to their surrounding physiochemical characteristics which define the ecological background of these species. The findings are not surprising in view of the current understanding of physiochemical parameters and freshwater fish assemblages in Fiji. In the correlation test particular physiochemical values were shown to influence the fish assemblages. As seen in the analysis the total abundance and species richness of fish for the 80 stations sampled is negatively correlated with turbidity and is significant.

A number of studies have noted the detrimental effects of increased turbidity on stream fauna and flora. Native fishes such as gobies and gudgeons that are bottom dwelling are

reliant on benthic food; increased sediments and turbidity smothers this habitats and benthic food sources and affects visual predator prey relationships (Bonner & Wilde, 2002; Jenkins et al., 2010). These turbid conditions could possibly favor species such as Anguilla obscura which was found only in Nakawaqa stream where turbidity readings were highest compared to the other two streams.

The Spearman Rank correlation test indicates a positive and significant correlation of conductivity across the 80 sampling stations with fish abundance and species richness. This could primarily be due to tidal influence and the position in catchment. Since tidal influence is stronger in the lower reaches of the three streams surveyed, it will therefore result in higher conductivity reading and this is directly linked to position in the catchment. Because the lower reaches of the three streams had greater abundance and species richness which helps to account for this significant correlation.

A negative and significant result was also noted for the correlation of pH and fish abundance per station. Overall, these values could be important in predicting the effects of environmental fluctuations on future fish populations. However, determining the physiological optima for any species of fish for one particular physicochemical or climatic variable is complicated. Many factors, such as seasonality, life history stage, reproductive stage, food availability and migration could obscure these connections (Jenkins & Jupiter, 2011; McDowall, 2010; Walter et al., 2012).

5.3.2 Freshwater fish habitat and micro-habitat associations The formulation of watershed conservation plans will require the understanding of the relationship between biodiversity and ecosystem functions. Several studies have proposed the mechanisms responsible for the distribution freshwater fishes in the Oceania region (McDowall, 1998a; Pusey et al., 1995; Pusey & Kennard, 1996). The majority of the freshwater fishes in Fiji are of marine origin and the early stages of their lifecycle are reliant on accessing the marine environment. Therefore, fish diversity decreases upstream because of less diverse habitats due to natural and manmade barriers to fish movement.

This study found clear association between fish assemblages, habitat and micro-habitat variables.

Variation in fish assemblages across the streams is explained best by differences in catchment size (i.e., depth, width, slope, discharge) and other variables linked to stream size. Differences in environmental conditions between the three catchments suggested that the catchment hydrology was an important factor for this study. Of the habitat and micro-habitat variables structuring the fish assemblages across the three streams; the altitude, volume of water and canopy cover were the most important factors affecting the assemblages, especially the food fishes normally targeted by villagers.

The flagtails Kuhlia rupestris and Kuhlia marginata are reliant on having a reasonable amount of habitable space i.e. sections of streams which have greater depth and width which will therefore equate to a greater volume of water. Eleotris fusca is most often found under cover and specializes in ambushing its prey (Leberer & Nelson, 2001). The result of this study reaffirms the global imperative of maintaining natural flow regimes for the conservations of freshwater fishes.

5.4 Study considerations This is the first extensive study to be undertaken in wadeable streams of Fiji utilizing a single sampling approach. It includes a greater number of details on the habitats and micro-habitats within a stream compared to previous studies in Fiji. The findings specifically have the potential of several freshwater fish species to serve as bioindicators in rivers and streams of Fiji and the Oceania. Since fish are located in the upper part of the trophic chain and require different habitats and connectivity through the stream network for the completion of their lifecycle, it makes freshwater fish assemblages a sensitive part of fluvial systems (Fausch et al., 1990). Furthermore, their major societal visibility makes fish a useful indicator to measure environmental degradation (Fausch et al., 1990).

The study found that the freshwater fish in Nakorotubu exhibit characteristic responses to the surrounding environmental conditions such as the within stream hydrology and water quality. These results mirror those of several other studies carried out in other countries. Interestingly, despite having the smallest catchment, Nakawaqa lower reach still exhibited faunal assemblages similar to Taveu and Vucinivola lower. This is in conformity to Jenkins & Mailautoka (2009) findings in Vanua Levu; where lower reach sites were relatively similar, even under different catchment size and forest cover.

Overall, the four species Eleotris fusca, Kuhlia rupestris, K. marginata, and Giuris margaritacea would be recommended as the most promising choices for indicator taxa (stream health) in wadeable streams; because these species span a range of habitat types and feeding guilds, and are significantly affected by position in catchment, volume of water and canopy cover. Moreover, this species can easily be identified by villagers with minimal taxonomic training for short and/or longer monitoring studies. The findings of this study, particularly in regards to the importance volume of water to native freshwater food fishes highlights the importance of maintaining natural flow regimes for the conservation of freshwater fishes. For many rural inland villages in Fiji, the native food fish aforementioned represent important sources of protein.

Furthermore, plans are currently underway on the feasibility of hydroelectricity production for the district of Nakorotubu. A workshop conducted by USP found that there was a possibility of generating up to 100kW of power from a local stream at Saioko village (USP, 2012). This proposed dam will block the migration of freshwater fish and change the hydrology of the stream system. There is time to delay the decision until there is better information from all relevant stakeholders. As mentioned earlier, maintaining natural flow regimes plays an important role for the food fishes; and building a dam could lead to the extirpation of endemics fishes found in this catchment and the depletion of food fishes such as flagtails and gudgeons. However, it is possible that eels may increase in abundance and biomass within the small lake created by this dam.

Worldwide there is ongoing debate and research on the effect of dams on riverine communities. Changes in riverine habitats brought about by anthropogenic actions are a well-documented cause of declining fish populations (Bunn & Arthington, 2002; Dudgeon et al., 2006; Naiman & Dudgeon, 2011). Although in Fiji there has not been any study undertaken on the effects of hydro-dams on riverine fauna, especially focusing on the magnitude of not just on abundance, species diversity, and biomass within the catchment but also the effects on nearby catchments outside the project footprint area. If the project does go ahead it presents an opportunity for further research on the effects of small hydro-dams on Fiji’s riverine fauna and flora.

5.5 Limitations of the study The overall results from the study advocates the importance of altitude, volume of water and canopy cover for food fishes in Fiji and the various physiochemical parameters that affect fish assemblages in wadeable streams. However, this study accepted a number of limitations. To understand local ecological communities requires understanding at broad spatial and long temporal scales (Lucas & Baras, 2000); owing to the inherent nature of natural systems which are subject to spatial and temporal variability due to changing rates of biotic (e.g. recruitment, competition, predation) and abiotic (e.g. habitat, water quality) factors (for reviews, see Jackson, et al., 2001), which in turn affects freshwater fish assemblages (Jenkins & Jupiter, 2011; Pusey et al., 1993, 1995; Pusey & Kennard, 1996; Pusey et al., 2000; Rayner et al., 2008; Russell et al., 2003).

This study was limited to a single point in time and thus represents a single temporal snapshot. Despite the little variation in fish assemblages over the three streams that were re-sampled in the dry season. The same could be stated for correlations of water quality and fish assemblages because determining the physiological optima for any fish species or climatic variable is complicated (Lomeli, 2011). These connections could be obscured by factors such as seasonality, migration, reproductive stage and food availability (Lomeli, 2011). These processes no doubt had varying degrees of influence between areas and among sites in this study. Additionally, the manner in which the electrofishing

was undertaken was subject to variation due to different levels of catchability among species; small gobies such as Stiphodon rutilaureus are harder to catch compared to larger fish such as eels that are easily seen when stunned. Moreover, within a stream several environmental variables (e.g. temperature, conductivity, turbidity and substrate type) are known to affect electrofishing catchability (Speas et al., 2004). For instance, research in the Colorado river found that the catchability of brown trout using an electrofisher was higher over rocky shorelines than sand–silt shorelines (Speas et al., 2004). The same may also be happening in the three streams surveyed in Nakorotubu as there were changes in average substrate composition from lower to upper reach sites. Data recording itself could have possibly experienced minor inaccurate in-situ species identification. Individual species in the family Anguillidae, Eleotridae, Gobiidae and Syngnathidae may be hard to identify especially in juvenile stages.

Another limitation of the study was the small number of readings taken for water velocity per sampling station which was due to time and budget constraints. For a thorough investigation on the effects of velocity on stream fish assemblages it would have been ideal to gather more readings at each station. It has been inferred from the current study that the bulk of the species in Nakorotubu prefer waters that are not stagnant; especially the goby Sicyopus zosterophorum which is seemingly a more rheophilic species in contrast to the other fish assemblages. Nonetheless, the findings presented here and the importance of volume of water on freshwater food fishes highlights the need for maintaining riverine connectivity for food security in rural Fijian communities.

5.6 Conclusion and recommendations The result of this thesis clearly highlights the importance of maintaining natural flow regimes for aquatic fauna. The maintenance of natural flow connectivity is critically vital for the food fishes of Fiji. It is important that the natural flow regimes and habitats in rivers and streams in Fiji are protected to ensure a continuous source of protein from

native fishes for rural inland villages and to maintain the diversity of freshwater fish assemblages in Fiji.

This study also provided insight into the longitudinal zonation of freshwater fish assemblages in wadeable streams and position in catchment was found to be significant factor affecting the fish assemblages. Sampling at different sections of the stream found that the lower reaches of streams had the highest abundance and species richness. The study also found that lower reach fish assemblages was significantly different from mid and upper reach fish assemblages. This clear distinction in lower reach fish assemblages and species attenuation with altitude has been well documented by Jenkins & Jupiter (2011) in Vanua Levu.

Given the limited scope of study the findings clearly substantiate the need to carry out further research in regards to volume of water on fish assemblages in Fiji. Anecdotal evidence gathered from several rural inland villagers in the province of Nadroga, Naitasiri and Namosi have pointed out that some of the native food fishes (e.g. mullets, flagtails) that use to traverse their iqoliqoli are no longer found in their fishing grounds and/or have decreased in abundance. A majority of the villagers believe that this is primarily due to reduction in the water levels and increase in sedimentation and that the changing climate and uncontrolled slash burn techniques are the primary causes of the demise of this once productive insular fishery (pers. obs).

The results also provide clear directions for future validating studies that address missing ecological information on the freshwater fish species such as connectivity among neighboring catchments, status of these streams as sources or sinks will also be critical. A more detailed study on the habitats, microhabitats and hydrology of each site and the species therein will be critical in understanding the roles these factors play on fish assemblages. Ideally, such studies should be carried out over an extended temporal scale

to help for greater understanding and account for natural variations that may affect the status of the fish assemblage. Nonetheless, to ensure the perpetual supply of resources by freshwater systems will entail the need for maintaining natural flow connectivity from the headwaters into the marine environment and the associated habitats therein.

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