Cottesloe Ecosystem Research Project: Structurally Complex Reef Habitats Enrich the Diversity and Abundance of Fish Species

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1 Cottesloe Ecosystem Research Project: Structurally Complex Reef Habitats Enrich the Diversity and Abundance of Fish Species Claudia Berson, Phoebe Beurteaux, Grace Chan, Harveen Ford, Milly Godwin, Lucy Jeffreys, Tessa Ramshaw, Megan Robins Abstract In understanding associations between habitat zones and fish abundance and diversity, marine environments can implement well developed management schemes to ensure improved conservation for future generations. In 2001 the Cottesloe Fish Habitat Protection Area (CFHPA) was developed with an aim to conserve a reef system that is under vast anthropogenic stresses due to its close proximity and easy access to a densely populated coastal region. Our study hypothesized that structurally complex environments, where there is an abundant variety of substratum, will display a greater species richness and diversity. Fish surveys were conducted from three predetermined zones; these included the lagoon, the flat reef and the broken reef. All zones were defined by different benthic topography, increasing in complexity further from the shoreline. The main species found to inhabit the CFHPA include Coris auricularis (C.aricularis), Pelates octolineatus (P.octolineatus ), Siganus fuscescens (S.fuscescens) and Notolabrus parilus (N.parilus). It was observed that fish stocks increased in the presence of habitats containing primarily rock substratum and abundance increased offshore. The data showed no significant correlation between the complexity of benthic habitats and fish abundance and diversity, therefore rejecting our hypothesis. The disparity in the results may be explained by human error, via the identification and counting of fish, and the variation in weather each year. Had the experiment been carried out frequently throughout the year in various weather conditions, with more experienced surveyors, the results could be more accurate. Providing a better understanding of the relationship between habitat structure and fish stocks would allow for greater insight into improving management to our marine environments for effective conservation. Keywords: conservation, habitat, fish, species abundance, species diversity, Cottesloe Reef Introduction Protected areas and sanctuary zones are fundamental for the management of the marine environment, which includes the conservation of biodiversity and preservation of ecological processes. Anthropogenic influences such as fishing, pollution, coastal development, introduced 1

2 pest and catchment activities put an increasing pressure on the marine system, emphasising the importance of developing well managed protected areas especially in densely populated coastal zones (Marine Park Authority 2008). Biologically diverse habitats are defined by their ability to produce suitable living conditions for species to allow for breeding, feeding, reproducing and shelter. The importance of habitat selection to the co-existence and success of marine species is influenced by numerous abiotic and biotic factors. The abundance and diversity of fish species illustrate a strong relationship with the structural complexity of their habitat (Bell & Galzin 1984). Understanding this relationship in a marine environment is an integral part of being able to construct effective and suitable management plans for influential conservation. Past research has shown that successfully well-managed zones have a strong positive influence on the growth, diversity and abundance of fish species utilizing the area (Barret et al. 2007). Evans and Russ (2004) have found marine reserves along the Whitsundays and Palm Islands with no-take policies are producing 3.6 times the normal abundance of coral trout found fished areas in the same region. CFHPA is a 1.5km wide reef shelf located along the Western Australian Coast in the Indian Ocean with a Northern boundary of North Street in Cottesloe extending approximately 4.4km southwards towards the Town of Mosman Park (Department of Fisheries 2001). It is described as a limestone reef comprised of elevated platforms; water eroded outcrops and pinnacles with sporadic areas of sand, seagrass and kelp beds, hence creating a structurally complex system with a range of diverse substratum (Department of Fisheries 2010). The habitat provides suitable breeding grounds, nursing areas and shelter for a diverse range of species including the Port Jackson Shark (Heterodontus portusjacksoni), Squid (Teuthida) and Weedy sea dragon (Phyllopteryx taeniolatus) (Department of Fisheries 2001). The reef system fringes on a highly populated coastal area, located in close proximity to popular tourist attraction, Cottesloe Beach. This additional anthropogenic pressure classes the biologically diverse reef as a vulnerable, high-risk environment, thus emphasises the need for well-managed protection from the Cottesloe Marine Protection Group (CMPG). The objective of the study was to determine relationships between the structural complexity of a habitat and the diversity and abundance of fish species in the CFHPA. The Cottesloe Reef is comprised of three different habitat divisions including the lagoon principally comprised of sand substratum with patchy areas of seagrass and singular rocks, the flat reef which was primarily uniform rocky cover, and the broken reef defined by a mixture of rock cover, kelp beds and sandy 2

3 areas with varying depth. The CFHPA has a reef system that develops in complexity as it moves offshore; the broken reef zone has the properties of a typical reef structure due to its diverse range of depth and substrata. It is suggested by Schlosser (1987) that fish communities living in areas of greater structural complexity are predicted to have greater species diversity. Scientific understanding about the relationship between habitat and fish communities is vital when implementing effective conservation plan and policies. Method Study Site The site at which we conducted our investigation was the CFHPA on the coast of Western Australia at a longitude and latitude of 32 00'28.9"S '05.3"E. The section of Cottesloe Reef that we sampled, lies from Beach Street Cottesloe and extends approximately 50m south and 120m offshore (Figure 2). It is positioned on a limestone shelf, which extends approximately 1.5 kilometres offshore. The reef network varies in depth according to the contours of the underwater terrain (Department of Fisheries 2010) and encompasses varying limestone-elevated platforms and water eroded outcrop and pinnacles. The CFHPA was divided into North and South zones to carry out field experiments (Figure 1). These two zones are comprised of four different habitat zones, respectively labelled in order of increasing distance from the shore; lagoon, flat reef, broken reef and front reef (Figure 2). For this experiment, sampling was performed in the lagoon, flat reef and broken reef. NORTH SOUTH Figure 1. Aerial photo of Cottesloe Reef showing the division of the north and south region. 3

40m REEF 40m REEF 40m REEF BROKEN REEF FLAT REEF LAGOON 50m FRONT REEF Figure 2. Aerial photo showing the division of the three habitat zones at Cottesloe Reef.

4 40m REEF 40m REEF 40m REEF BROKEN REEF FLAT REEF LAGOON 50m FRONT REEF Figure 2. Aerial photo showing the division of the three habitat zones at Cottesloe Reef. Numbered boxes indicate habitat zones: 1 - Lagoon, 2 - Flat Reef, 3 - Broken Reef, 4 - Front Reef. Experimental Design for Fish Community Sampling The data was collected to study the diversity and abundance of fish species in the various habitat zones to be compared with data acquired from previous years. The fish data was collected by groups of snorkelers who were assigned to work in either the north or south zones (Figure 1). In each of the three allocated habitat zones, groups of four snorkelers laid down a 10m transect along the sea floor, parallel to the division of the zones. One member swam the length of the transect line with an underwater camera in hand, and another counted and identified any fish species observed within a 5m diameter of the line. These observations were recorded on a waterproof data table (Appendix 1) at the end of the 10m swim. A species identification chart, constructed prior the swim, was used to assist in the identification of common fish species in the Cottesloe Reef ecosystem. For each habitat zone, the 10m transect swim was repeated four times in different locations within the zone, resulting a total of twelve replicates per group. It is assumed that other groups and previous years followed the same sampling technique for their data collection. 4

5 Data Analysis The raw data collected from each group was collated into a Microsoft Excel spreadsheet for further analysis. Data from the years 2012, 2013 and 2014 were organized in the spreadsheet where the total number of sightings for each species across the habitats over the three years was calculated. The top four most sighted fish species, were to be the ones used in our final analysis. To look at the abundance of fish species in each zone, the sightings over the last three years was averaged out (Figure 3). To look at diversity, the number of different fish species sighted in each of the different habitat zones, in each year was calculated (Figure 4). When analyzing the data we assumed that all groups had followed a similar procedure during data collection and processing. Results Species diversity over 2012, 2013 and 2014 was the greatest in the flat reef (Figure 3). The heightened diversity in the flat reef habitat is apparent across all years. This is not the case for the lagoon and broken reef, which show fluctuations. In 2012 and 2014, the lagoon holds the second greatest number of species, followed by the broken reef. This is contrary in 2013, where the lagoon appears to be the least diverse habitat. Figure 3. Total average fish diversity across the three habitat zones at the Cottesloe Reef over a period of three years. Error bars represent standard error across the data. 5

The average individual abundance of the four most abundant fish species were analysed within each habitat zone (Figure 4). C.aricularis, P.octolineatus and N.

6 The average individual abundance of the four most abundant fish species were analysed within each habitat zone (Figure 4). C.aricularis, P.octolineatus and N.parilus were most abundant in the broken reef; whereas for S.fuscescens, the flat reef showed greatest abundance and the broken reef the least. C.auricularis and N.parilus both indicated an increasing abundance of fish towards the offshore reefs with the lagoon having the lowest abundance followed by the flat reef. This order is overseen for P.octolineatus and S.fuscescens, which do not reflect any orderly patterns. The patterns revealed from the study of four focal species (Figure 4) differs from those unveiled in Figure 3 where all species were considered. In this instance, the broken reef is the primary habitat for fish species (Figure 4). Figure 4. Average fish abundance of the four most abundant fish species across the three habitat zones at the Cottesloe Reef over a period of three years. Error bars represent standard error across the data. Discussion We hypothesized that the abundance and diversity of fish species sited in the CFHPA would increase in an offshore direction towards the more structurally complex outer reef. Our predictions entailed the offshore and high relief characteristics of broken reef will provide a stronger ecosystem with more complex structures and, therefore, enhance the diversity and abundance of fish species observed in this habitat. Our results rejected this statement. The broken reef was seen as a highly 6

7 habitable location, having the greatest abundance of the four most common fish species (Figure 4), whereas the flat reef was the site for enhanced fish diversity (Figure 3). The complexity of the habitat structure has a major influence on the composition of fish diversity in reef networks (Komyakova et al. 2013). Fish species will associate with habitats that support food requirements, provide shelter from wave exposure, protection from predators and sustain breeding (Friedlander et al. 2003). Compared to the lagoon habitat zone, both the flat and broken reef sustained features that indicate greater structural complexity. Studies show that, in Western Australia specifically, high relief limestone reefs attract greater fish diversity and abundance (Harmon et al. 2003). The associated increased depths and characterised ledges, overhangs and crevices provide sites for refuge and nutrient/dietary requirements. With this knowledge, it is understandable that the results indicate, in most instances, that the broken and flat reefs are more abundant in terms of fish activities than the lagoon habitat zone. In order to assess the fish abundance within the three habitat zones, we analyzed four focal fish species that were heavily sighted in the CFHPA over the past three years C.aricularis, P.octolineatus, N.parilus and S.fuscescens. With reference to Figure 4, the hypothesis is supported offshore habitats support a greater abundance of species. Both C.auricularis and N.parilus reflect an ideal abundance gradient abundance increases progressively further offshore throughout all three zones. Our predictions and understandings inferred that the lagoon would present a fairly unsuitable habitat for fish as this zone lacks habitat structure however when analyzing the presence of fish communities in the lagoon habitat in Figure 4, our results proved otherwise. Both the P.octolineatus and S.fuscescens demonstrated the second most abundant habitat as the lagoon, validating the importance of all habitats. Even though there is variation in the abundance of species sightings throughout the habitat zones, there are adequate sightings of each species across all the zones. These sightings suggest that fish species have a level of resilience to reside in multiple environments, as well as the ability to adapt throughout. Nevertheless it is evident that habitat preferences, such as the strongly affiliated presence of P.octolineatus in the Broken reef, suggests ecological niches do exist for individual species, which, thus, accounts for associated differences in abundance. The diversity of differing fish species was assessed by counting and categorizing sited species according to the zone sighted in (Figure 3). The results attained rejected the hypothesis, as diversity 7

8 did not appear to increase progressively as you move from the lagoon to broken reef. Alternatively, the flat reef became apparent as the most diverse throughout 2012, 2013 and The increase in fish diversity, seen in this low relief reef system, suggests habitat specialization and partitioning among common reef fishes. From Figure 4, which studies fish abundance, it could be ascertained that whilst the broken reef has the structural complexity to support a greater number of species, the flat reef is subject to conditions ideal for a wider range of species. As the flat reef is situated in the middle of the habitat zone (i.e. in between the lagoon and broken reef), this region may be subject to habitat overlaps from species moving between habitat zones. Limitations presented throughout the duration of this research were due to human and experimental error, which could attribute to the variation in results and the partial rejection of our hypothesis. Due to the nature of this experiment being conducted by inexperienced students, there were inconsistencies evident in data collection. Discrepancies were apparent in fish identification and counting due to variations in individual human interpretation. Increasing replicates of fieldwork would be favourable to sustain an extensive array of data. The amount of available information with increased replication would enhance the accuracy and minimise the standard error between data. Additionally the weather would have played a major role in fish attendance. Facilitating fieldwork at more frequent intervals throughout the year could potentially enhance the results to reflect species variation better, and therefore amplify a greater understanding of habitat preference. In conclusion, our results rejected the hypothesis. The general trend associated with fish species abundance saw three out of the four focal species being most abundant in the furthest habitat zone, the broken reef. However, in only two of these cases, the abundance gradient progressed with offshore habitats. With regards to diversity, the results found that the flat reef had the greatest average fish diversity, which deviates from our original hypothesis. By assessing individual species, rather than focusing only on a general scale, we were able to determine the value of each zone, which is greatly specific to individual species. The overall aim of protected areas is to preserve the marine environment from anthropogenic issues from the nearby densely populated city. All habitat zones within this location hold value for a variety of fish species and, therefore, we propose that the protection and preservation of the CFHPA be pursued further at more frequent times in the year, to cover a range of fluctuating factors such as ph, weather and interspecies relationships to ensure an accurate portrayal of the region and to continually preserve the existing thriving ecosystem. 8

9 Appendix 1 Habitat (Lagoon, Flat Reef or Broken Reef) Species Leatherjacket Goatfish W.King Wrasse Brown Spot Wrasse W.Stripe Trumpeter Bullseye Tarwine Bream Parma Whiting Boxfish Herring Footballer Sweep Sea Sweep Banded Sweep Blowfish Old Wife Morwong Tailor Red Striped cardinal Stingray Other: Description of Substratum (e.g. sand, kelp beds, reef) 9

10 References Barrett, N., Edgar, G., Buxton, C. and Haddon, M Changes in fish assemblages following 10 years of protection in Tasmanian marine protected areas. Journal of Experimental Marine Biology and Ecology, 345, Department of Fisheries Cottesloe Reef Fish Habitat Protection Area. Perth, pp Department of Fisheries Plan of Management for the Cottesloe Reef Fish Habitat Protection Area. Fisheries Management Paper No. 155, pp Evans, R. and Russ, G Larger biomass of targeted reef fish in no-take marine reserves on the Great Barrier Reef, Australia. Aquatic Conservation: Marine and Freshwater Ecosystems, 14, Friedlander, A., Brown, E., Jokiel, P., Smith, W. and Rodgers, K Effects of habitat, wave exposure and marine protected area status on coral reef fish assemblages in the Hawaiian archipelago. Coral Reefs, 22(3), Harman, N., Harvey, E. and Kendrick, G Differences in fish assemblages from different reef habitats at Hamelin Bay, south-western Australia. Marine and Freshwater Research, 54(2), Komyakova, V Habitat characteristics as determinants of the local diversity and structure of coral reef fish communities. Master of Science, James Cook University. Komyakova, V. Munday, P. and Jones, G Relative importance of coral cover, habitat complexity and diversity in determining the structure of reef fish communities. PloS one, 8. Marine Parks Authority A review of benefits of marine protected areas and related zoning considerations. Available from: Marine Parks Authority Secretariat. Schlosser, I A conceptual framework for fish communities in small warmwater streams. Matthews WJ, Heins DC (eds) Community and evolutionary ecology of North American stream fishes. University of Oklahoma Press, Norman, pp

11 Press Release The Cottesloe Fish Habitat Protection Area (CFHPA) is a protected zone located in Cottesloe, Perth. It is 1.5 km wide and is diverse in its underwater structure and is rich in marine organisms. On the 29th of March 2014, students from the University of Western Australia sampled a section of this region, in an effort to see if the composition of different marine environments had an effect on the abundance and diversity of different fish species. The region which was sampled, had three main sections; the lagoon, the section closest to the shore, consisting of deep sandy bottom with large beds of sea grass, the flat reef, about 20m from shore, which was shallow, with many flat reef segments and the broken reef, which was the section furthest out containing larger reef structures and denser vegetation. The broken reef had the greatest structural differences with big coral ledges, a large quantity of different weeds and corals and deep crevices for protection against predators. We predicted the broken reef would have the highest abundance and diversity of fish species as we deduced that the broken reef was the most structurally complex site, where species would have more food and shelter to live efficiently. Research showed that biologically diverse habitats, like the broken reef, had the characteristics best suited for breeding, feeding and reproducing. We therefore felt confident stating the broken reef would have the highest abundance and diversity of fish species. In addition we predicted this trend would also increase from the lagoon to the broken reef, with the least diverse and abundant species being found in the lagoon and vice versa in the broken reef. After we analysed our data, it was concluded that our predictions were rejected. We found that the height of diversity was located in the flat reef, despite having initially thought the broken reef had better structural complexity to support a larger number of fish, the conditions the flat reef, seemed to be a more viable living condition for more species of fish. In regards to the abundance of fish, our findings were much closer to what we predicted. Three out of the four species we focussed on, had the largest numbers in the broken reef, however only two of those species gradually increased from lagoon to broken reef like we initially thought. Overall we concluded that the management of the CFHPA should continue, as we have seen steady progress been made with the abundance and diversity of fish species over the last few years, but more constant monitoring should be carried out in the future to see how the CFHPA performs in different conditions during the year (e.g. weather, ph, interspecies relationships) and how this might affect the abundance and diversity of fish species. 11

The marine habitat gradient of Cottesloe Reef: increasing fish abundance and diversity towards outer reef

The marine habitat gradient of Cottesloe Reef: increasing fish abundance and diversity towards outer reef Tim Angeloni (20950811), Leah Campbell (21112688), Harrison Davis 20916292), Oliver Fredriksson