Vol. 503: 205–218, 2014 MARINE ECOLOGY PROGRESS SERIES Published April 29 doi: 10.3354/meps10733 Mar Ecol Prog Ser Nektonic assemblages determined from baited underwater video in protected versus unprotected shallow seagrass meadows on Kangaroo Island, South Australia Sasha K. Whitmarsh1,*, Peter G. Fairweather1, Daniel J. Brock2, David Miller3 1School of Biological Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia 2Coast and Marine Program, Kangaroo Island Natural Resources Management Board, 35 Dauncey Street, Kingscote, Kangaroo Island, South Australia 5223, Australia 3Department of Environment, Water and Natural Resources, 1 Richmond Road, Keswick, South Australia 5035, Australia ABSTRACT: As the number of marine protected areas grows worldwide, it is important to under- stand how existing protected areas have functioned. Baited remote underwater video stations (BRUVS) are becoming a widely used technique for monitoring reef fish, but with few studies hav- ing so far used BRUVS in seagrass meadows, it remains unclear how they perform within these habitats. The aims of this study were to trial the use of BRUVS in shallow seagrass habitats and to compare animals observed at Pelican Lagoon Aquatic Reserve to 2 broadly similar locations on Kangaroo Island that have had no protection. BRUVS identified 47 distinguishable taxa from 5 phyla, with the majority (79%) of those being fishes. Assemblages taking into account relative abundances were not significantly different between protected and unprotected areas; however, species compositions alone varied significantly across all 3 locations. Only 2 out of 18 commer- cially and/or recreationally targeted species had a higher abundance within the reserve. Overall, BRUVS were found to be suitable for use in seagrass habitats; however, some limitations (particu- larly the potential for obstruction of the camera by seagrass blades) may exist. KEY WORDS: BRUVS · Conservation · Fish · Habitat description · Marine protected area · Method development · Posidonia · Video Resale or republication not permitted without written consent of the publisher INTRODUCTION levels. Aside from restricted-access (or ‘no-go’) zones, the highest level of protection for an area is As threats such as climate change, overfishing and generally a sanctuary (or ‘no-take’) zone, where fish- pollution increase pressure on the world’s marine ing, dredging, mining and other potentially harmful ecosystems, governments are looking for ways to extractive activities are prohibited (Agardy et al. manage these threats. The use of marine protected 2003); these areas are often referred to as ‘reserves’. areas is one option that is becoming increasingly Sanctuary zones have been shown, on average, to popular as a tool to conserve biodiversity and man- increase diversity, abundance, size and biomass for a age oceanic resources (Warner & Pomeroy 2012). range of fish species in both temperate and tropical Marine protected areas are locations set aside within areas worldwide (Halpern & Warner 2002, Halpern the ocean for conservation, which vary in protection 2003, Lester et al. 2009, Stewart et al. 2009) and also *Corresponding author: [email protected] © Inter-Research 2014 · www.int-res.com 206 Mar Ecol Prog Ser 503: 205–218, 2014 increase the diversity and abundance of reef algae monitor seagrass habitat. Other video techniques, and invertebrates (Edgar & Barrett 1999). however, have been used in seagrass (e.g. Smith et An effective monitoring program is essential for al. 2011). any marine protected or otherwise managed area to The objectives of this study were to investigate assess whether its goals are being achieved. Monitor- nektonic biota in 3 shallow seagrass areas at Kanga- ing is needed to ensure that a reserve is functioning roo Island, South Australia, using BRUVS. In particu- as intended and to provide feedback to adapt man- lar, the aims of this paper were (1) to trial the feasibil- agement strategies over time where necessary. ity of using of BRUVS for monitoring programs in Despite the well-known need for monitoring, many local seagrass habitats; and (2) to determine how sev- protected areas fail to have adequate plans in place, eral decades of protection from fishing affects assem- and this is probably because of the perceived high blages in a protected seagrass habitat at Kangaroo cost of long-term monitoring, among other chal- Island as compared to similar, but unprotected, areas lenges (Day 2008, Warner & Pomeroy 2012). To at the same Island. reduce costs of monitoring, more efficient and cost- Specifically, we predicted that (1) BRUVS would effective methods and techniques must be developed observe a wide range of nektonic species, demon- and trialled for specific habitat types. Many temper- strating its suitability for monitoring in seagrass; (2) ate marine reserves will include significant areas of assemblages observed via BRUVS would differ seagrass meadow, a habitat that has been little stud- between sites; (3) sanctuary-zone protection status ied in terms of its response to protection. For exam- would have a different composition structure from ple, South Australia’s protected areas have had min- unprotected sites; and (4) higher abundances of fish- imal ongoing monitoring, and it is unclear how these eries-targeted species would be seen in a reserve reserves have been operating. Only 2 protected reef compared to unprotected sites. areas in South Australia have been studied for per- formance: Point Labatt Marine Reserve (Currie & Sorokin 2009) and Aldinga Reef Aquatic Reserve METHODS (Edgar & Stuart-Smith 2009), with neither of those containing seagrass-dominated habitats. Sampling sites Seagrasses are important components of many coastal ecosystems (Hemminga & Duarte 2000). Pelican Lagoon Aquatic Reserve (PLAR) on Kanga- Their roots and rhizomes stabilise sediment and pre- roo Island, South Australia, is one of that state’s old- vent coastal erosion (Duarte 2002, Orth et al. 2006). est protected areas, having been declared in 1971 (as Seagrasses also provide shelter, habitat and foraging the American River Aquatic Reserve); however, there sites for many fish species (Hemminga & Duarte has been very little research undertaken in this area 2000, Beck et al. 2001, Jackson et al. 2001, Gillanders to date. The reserve covers an area of 15.2 km2 and is 2006), with studies having shown that loss of sea- composed mainly of shallow, sheltered seagrass grass habitats can result in reductions in fish recruit- meadows and tidal flats, with some deeper pools up ment, density and biomass (Pihl et al. 2006). to 10 m in depth (PIRSA 2012). The reserve was set Baited remote underwater video stations (BRUVS) up primarily to protect juvenile fish stocks that used have often been used in monitoring programs in pro- this area as a key nursery ground (PIRSA 2012). The tected areas (e.g. Cappo et al. 2004, Malcolm et al. reserve is also thought to be a refuge for adult fish 2007, McKinley et al. 2011, Gladstone et al. 2012). and is frequented by many different species of water The non-destructive nature of this method along with birds (Kinloch et al. 2007). The key economic fish its ease of use, replicability and ability to detect a species occupying this area are King George whiting range of fish species (Harvey et al. 2007) make Sillaginoides punctata, southern sea garfish Hypo - BRUVS sampling suitable for such monitoring pro- rhamphus melanochir and Western Australian salmon grams. Currently, BRUVS have been used mainly in Arripis truttaceus (Kinloch et al. 2007). The likeli- coral or rocky reef habitats (e.g. Cappo et al. 2007, hood of illegal poaching within the reserve is low 2011, Watson et al. 2007), with some use in other because of vigilant oversight by residents within the habitats such as unconsolidated substrates or estuar- community (PIRSA 2012). Other shallow seagrass- ies (e.g. McKinley et al. 2011, Harvey et al. 2012, dominated embayments on northeastern Kangaroo Schultz et al. 2012). Overall, few studies have used Island include Eastern Cove (EC) and Bay of Shoals BRUVS in seagrass (e.g. Gladstone et al. 2012), even (BoS), which had no protected status when this study though this method may have a great potential to was done. Whitmarsh et al.: Use of BRUVS in seagrass 207 location based on depth, limited proximity to each other and suitable habitat type (i.e. the seagrasses Posi- donia spp. being present). Sampling was conducted on January 16 to 20, 2012, during mostly sunny conditions with winds up to 20 knots. Water quality variables including salinity (ppt) and temperature (°C) were measured during sampling using a TPS WP-84 conductivity-salinity probe. Habitat description Habitat was assessed using the BRUVS (see below) field of view. After deployment, when the BRUVS and any disturbed sediment had settled (approximately 1 to 5 min), a still image was taken, and using SeaGIS TransectMeasure (www. seagis. com. au/ transect. html), the image was ana- lysed using a dot-point method, in which 100 points were randomly applied to the frame, and the habitat type (i.e. Posidonia spp., Halophila spp., Heterozostera spp., macroalgae, detritus, unconsolidated bare sub- strate, invertebrates) beneath each point was recorded. BRUVS sampling setup Fig. 1. Sampling locations in Kangaroo Island, South Australia, and their 5 sites selected for this study; BoS = Bay of Shoals (squares), EC = Eastern Cove Animal assemblages were investi- (circles), PLAR = Pelican Lagoon Aquatic Reserve (triangles). The seaward gated using BRUVS. Four replicate limit of the aquatic reserve is shown as a dotted line between ‘PLAR’ and ‘EC’. drops were conducted at each site in Only the eastern portion of PLAR could be sampled because of a lack of each location (total n = 60). Single seagrass and very shallow tidal flats in the western portion BRUVS units, as opposed to stereo, were used in this study because the Sampling was conducted at 3 locations on Kan - remote location compounded some logistical and garoo Island, South Australia: BoS (35.6179° S, vessel space restrictions.