Cabbage Tree Bay Aquatic Reserve, Manly

Manly Conservation Report

March 2019 – Samantha Goyen, BSc(Hons)

Introduction

Manly is a lively coastal community on the Northern Beaches of Sydney. Lifestyle and tourism revolve around the ocean, in particular the many iconic beaches, as well as the unique natural bushland and rich cultural heritage of the area. Manly is also considered to be a marine biodiversity hotspot in Sydney (Reef Life Survey, 2015). In addition, the northern beaches coastline and bushland contain 75 threatened native plant and animal species (Northern Beaches Council, 2019) making this area a truly unique natural asset. Each year, Manly hosts over 2.5 million visitors of which over half specifically come to enjoy the natural environment (Tourism research Australia, 2018). Residents of Manly are active and passionate about conserving the biodiversity and heritage of this spectacular region so we can all continue to enjoy it and learn from it into the future.

The Gayamaygal people

The Northern Beaches of Sydney were once occupied by the Aboriginal Gayamaygal clan. Kai’ymay is the placename given to Manly Bay (Attenbrow, 2002). Kai’ymay is a key site of early contact between Aboriginal people and the British in 1788 when Governor Phillip colonised Sydney. On observing the Aboriginal people of Kai’ymay he stated that “their confidence and Manly behaviour made me give the name of Manly Cove to this place” (Curby, 2001). The Gayamaygal were saltwater people who survived on a diet of fish and shellfish, where the women were especially skilled canoeists and fisherwomen (Karskens, 2009). The Northern Beaches has more than 300 Aboriginal sites which are still in reasonable condition, the oldest dating back over 6000 years ago (Northern Beaches Council, 2019). These sites include Middens (feeding sites), shelters, engravings and art remnants and are important evidence of Aboriginal Australia, providing valuable links to traditional culture.

Manly-Freshwater World Surfing Reserve

Manly is recognised as the birthplace of Australian surfing with over 100 years of surfing heritage. In 1915, Duke Kahanamoku gave his famous surfing demonstration at Freshwater beach beginning a wave of surfing enthusiasm across the country. Australiansurfing never looked back after the world’s first surfing championships were held at Manly beach in 1964. In 2010, the Manly-Freshwater World Surfing Reserve was declared recognising the historical, cultural and environmental values of these surfing beaches (National Surfing Reserves, 2019).

Cabbage Tree Bay Aquatic Reserve

Cabbage Tree Bay Aquatic Reserve is of high environmental, cultural and recreational value to the Manly community. As a west-facing embayment, it is naturally sheltered from the dominant south-easterly swells allowing for increased biodiversity (Turnbull et al., 2018) and is very popular with recreational scuba divers, snorkellers and swimmers. In 2002, following the successful lobbying by locals, Cabbage Tree Bay, was declared a ‘No Take’ Aquatic Reserve, covering an area of ~20 hectares. The reserve was an attempt to conserve its unique biodiversity and habitats as well as facilitateeducational activities and scientific research (Department of Primary Industries, 2019). ‘No Take’ means you are not permittedto fish by any method, mine, destroy marine life or collect dead or alive organisms including empty shells (Bell 2010). Since Cabbage Tree Bay gained Aquatic Reserve status, ~ 50 different invertebrate species, 160 fish species and 5 fish species listed as endangered or protected under the Fisheries Management Act 1994 have been recorded (DECCW Cabbage Tree Bay Aquatic Reserve: Draft Regulation and Implementation Strategy, 2010).

Habitat types and species

Within the reserve, a diversity of habitats and associated marine life can be found (Figure 1). The dominant habitat is the rocky reef which is densely covered with Ecklonia radiata (macroalgae) and sponges. The rocky reef provides complex habitat (rock platform, crevice, rock-pool, boulder and cobble) and therefore shelter for iconic species such as the wobbegong shark and cuttlefish as well as protected species including the weedy seadragon and the elegant wrasse (Department of Primary Industries, 2019). Pelagic species (large open water ranges) such as dusky whaler sharks and green sea turtles can be seen from February- June when the water is warmer. Southern Right and Humpback whales are also a common sight from May- November during their annual migration, first north to warmer sub-tropical waters where they mate and calve before returning south to Antarctic waters to feed (Department of the Environment and Water Resources, 2007). Often, mothers and calves will seek shelter in the protected waters of Manly.

In NSW, only 12 aquatic reserves exist, of which Cabbage Tree Bay accounted for most of the increased richness of large fish and increased biomass of targeted fish species (Figure 2) (Turnbull et al., 2018). This is thought to be due to the sheltered nature and habitat complexity of the bay, an active local community providing informal enforcement and full no-take protection (Turnbull et al., 2018). This unique aquatic reserve needs to be cherished to ensure sustainable use into the future for enjoyment, understanding and an ever- increasing tourism market.

East Australian Current (EAC)

Currently, the biggest threats to the persistence of Cabbage Tree Bay Aquatic Reserve and the surrounding marine environment are land based developments and pollution (i.e. stormwater runoff and plastic pollution), illegal fishing/collecting and climate change (DECCW Cabbage Tree Bay Aquatic Reserve: Draft Regulation and Implementation Strategy, 2010). With the intensification of the East Australian Current under climate change (Figure 4), Sydney is experiencing ocean warming two to three times faster than the global mean (Verges et al., 2014). This can significantly impact the distribution and diversity of marine species by shifting thermal zones and affecting dispersal patterns as well as making eastern Australia a potential hotspot for ecological modification (Verges et al., 2014). “Tropicalisation” (increase in the proportion of warm waterspecies) is being increasingly observed along the south east coast of Australia, with the majority of literature documenting increases in tropical fish (Figueria & Booth, 2010; Booth & Sear, 2018). For example tropical fish species such as the Moorish idol (Zanclus cornutus) are often seen in the aquatic reserve over Summer. Importantly, new research is showing that tropical corals are also expanding their range into Sydney, with Pocillopora aliciae and associated Pomacentridae fishes thriving in Manly (Booth & Sear, 2018).

Still, so little is understood about the changes happening in this dynamic environment and the potential competition between temperate and marine organisms. It is vital that research continues in this field and management plans strive to maintain the current levels biodiversity. Efforts to reduce the pressures from other threats such as fishing and pollution will help natural ecosystems cope with the inevitable effects of climate change.

Conclusions

The Manly area not only has unique biodiversity but also a unique network of businesses, organisations and individuals who are working passionately to ensure the protection of the ocean and the environment alongside local economic growth. There are many brilliant initiatives in place such as So Manly (Sustainable Organisations of Manly) who tackle plastic pollution and marine protection through grassroots community campaigns. The Manly Environment centre continue to educate the community and support research efforts while hands-on programs such as Operation Crayweed re-establish crayweed habitataround Manly, where it once flourished, and restore essential habitat and food supply for the marine biodiversity. Manly, and Cabbage Tree Bay in particular, sets an example for the rest of Sydney and highlights the benefits of having protected areas. This could not be more timely given the recent attempts to establish a Sydney Marine Park