ANALYSIS - The carrying capacity of fish farming has been identified as a way to conduct and promote sustainable aquaculture operations, writes Lucy Towers, TheFishSite Editor.
"Carrying capacity can be used to promote sustainable aquaculture," said Dr Carrie Byron, whilst presenting her doctorate work at the Gulf of Maine Research Institute (GMRI) Sea State Lecture series.
At present, there are many barriers to promoting a sustainable aquaculture industry. The biggest one is that there is a lack of public knowledge and understanding about aquaculture, which often contributes to a negative public perception and difficulties in setting up new coastal operations.
Therefore, in order for aquaculture to be sustainable, it needs to be understood and be a participatory process which involves everyone involved in, or affected by, aquaculture.
To do this, an ecosystem approch to aquaculture can be taken. This approach makes sure that there is no degradation of the environment and takes into account all sectors involved. One way to do this is through the carrying capacity approach.
"Carrying capacity is the number of individuals in a population of a particular species that the resources in the habitat can support," said Dr Byron.
Applying it to aquaculture, carrying capacity can be broke down into four types. Firstly, physical carrying capacity. This is simply the total area of farms that can be accommodated in a particular area or space. Production carrying capacity is the stocking density at which harvests are maximized. Ecological carrying capacity is the stocking or farm density above which would cause unacceptable ecological impacts and finally, social carrying capacity is the level of development above which would cause unacceptable social impacts.
In order to get a baseline for calculating carrying capacity working groups can be set up between all involved stakeholders. At these meetings issues and concrens about aquaculture can be raised and once the carrying capacity is determined, regulations can be defined.
The final carrying capacity can then be calculated using a computer model of the ecosystem and a mass balanced model. The goal is to increase the culture in shellfish biomass as much as possible without changing anything else in the system. It is that point just before a change is seen that is the ecological carrying capacity, said Dr Byron.
This framework of using carrying capacities for ecosystem based management for an ecological approach to aquaculture is easily transferrable to other areas that are also dealing with user conflict issues, concluded Dr Byron.