New Zealand king shag (Leucocarbo carunculatus) foraging distribution and use of mussel farms in Admiralty Bay, Marlborough Sounds
|Title||New Zealand king shag (Leucocarbo carunculatus) foraging distribution and use of mussel farms in Admiralty Bay, Marlborough Sounds|
|Publication Type||Journal Article|
|Year of Publication||2012|
|Authors||Fisher, PR, Boren, LJ|
|Type of Article||Article|
|Keywords||aquaculture, king shag, Leucocarbo carunculatus, mussel farm, survey method|
To date there has been no published information describing the relative abundance, behaviour or distribution of the New Zealand king shag (Leucocarbo carunculatus) within mussel farm areas, despite the sensitivity of the species to human disturbance and the potential overlap of its range with proposed development of marine aquaculture. Four survey methods were employed as part of a multi-species research programme to develop methods for surveying marine mammals and seabird populations in aquaculture management areas. Two of the techniques, involving continuous time- lapse photography of mussel farms and boat-based surveys through coastal farms were developed for this study. Time- lapse cameras showed that mussel farms buoys were used by king shags as temporary resting sites only. King shags were recorded on 36% of the farms (n = 44) from 13 surveys within inner Admiralty Bay. The low number of sightings within mussel farms suggests that farms are not important foraging or resting areas for king shags, at least in Admiralty Bay. The foraging range and density of king shags was not known before farms were developed, so no direct comparison or impact assessment can be made. Boat-based surveys were used to estimate the density of foraging shags, which showed that daily locations of foraging birds at sea can vary considerably on consecutive days and over the season. Previous environmental surveys to assess impacts of mussel farms on foraging areas are therefore unlikely to adequately represent the entire foraging range or most important feeding areas. The number of breeding pairs, chicks and nests was also found to vary considerably at colonies, dependent on when counts were undertaken during their protracted breeding season. Open water mid-bay aquaculture (shellfish and finfish) potentially poses a greater threat to king shags than ‘coastal ribbon development’, in terms of loss of open water habitat from farm structures, and loss of foraging habitat through modification to the water column (e.g., turbidity) and seabed. Given the lack of knowledge about the king shag population dynamics, diet and prey availability, there is an urgent requirement for more research to fill these gaps and also understand how we can conserve important shag feeding areas and associated marine environment through sustainable management of aquaculture.