Fish and habitats Greg Jenkins Background At present, fish - PowerPoint PPT Presentation

Fish and habitats Greg Jenkins

Background • At present, fish assemblages are only well studied in Zostera seagrass. • We are unsure whether key species are reliant on specific habitats or whether alternative habitats can be utilised • This means the resilience of fish populations to habitat loss and the need for protection of specific habitats to support fish populations is unclear

Objectives • To determine the specificity of fish habitat relationships in Western Port • To determine the resilience of fish populations to habitat loss through the use of alternative habitats • Improving understanding of the important values and resilience of specific asset areas already identified in Western Port from the perspective of fish biodiversity

Sampling sites + Amphibolis Bryozoan Caulerpa Rhodoliths + Reef/algae

Amphibolis

Caulerpa

Rhodoliths

Reef/algae

Bryozoan

Stereo-video sampling

Mini Otter-trawl sampling

Dominant fish species - Amphibolis

Ornate Cowfish - Flinders

Old Wife - Flinders

Sixspine Leatherjacket – Flinders

Little Weed Whiting – Flinders

Weedy Seadragon – Balnarring

Calamari – Point Leo

Dominant fish species – Reef/Algae

Silver trevally – Cat Bay

Gummy shark, Snook – Cat Bay

Dominant fish species – Caulerpa

Key fish species – Caulerpa

Fish species – Rhodoliths

Octopus – Rhodoliths

Fish species – Bryozoan

MDS plot comparing fish assemblages Standardise Samples by Total Transform: Log(X+1) Resemblance: S17 Bray Curtis similarity SeasonLocation 2D Stress: 0.05 Autumn Balnarring Spring Balnarring Autumn Cat Bay Spring Cat Bay Autumn Pt Leo Spring Pt Leo Autumn Flinders Spring Flinders

Differences between locations and seasons • Balnarring and Flinders were distinctive for bridled leatherjackets and weedy seadragons • Cat Bay and Pt Leo were distinctive for bluethroat wrasse. • Cat Bay was distinct from Point Leo in relation to silver trevally • Autumn was characterised by bridled and six-spine leatherjackets while spring was distinct for weedy seadragons

Conclusions • Amphibolis and Caulerpa had diverse and abundant fish assemblages comparable to Zostera • The assemblage of fish in Caulerpa was more similar to that in Zostera • Caulerpa , and to a lesser extent Amphibolis , may act as a refuge habitat in the case of Zostera loss • The nursery value of these habitats may be lower due to greater depth (both species) and exposure ( Amphibolis ) • Weedy seadragons appear to have a relatively specific requirement for Amphibolis beds on low profile sand/ reef

Acknowledgements Field work assistance: Brent Womersley, Tim Kenner, Andrew Brown Laboratory assistance: Tim Kenner Still photographs: Julian Finn, Mark Norman (MoV) Peter Macreadie (UTS) Funding: Melbourne Water Department of Sustainability and Environment Port Phillip Bay and Western Port Catchment Management Authority