Aquaculture does not operate in an ecological vacuum. Marine farms of bivalves and finfish, with their nets, buoys, and platforms, intertwine with the environment, forming a complex series of interactions.
Leftover food and the structures of aquaculture farms, acting as artificial reefs, attract fish, squid, crabs, and other aquatic organisms. This coexistence can have positive effects: increased biodiversity, protection of juveniles, and even feeding opportunities. But like in any story, there’s also a downside: potential transmission of diseases, competition for resources, and disturbances in the delicate balance of the ecosystem.
Understanding the interactions between aquaculture and the overall ecosystem is crucial for ensuring sustainable practices. This is where monitoring comes into play. Researchers have employed a variety of techniques to assess the impact of aquaculture on wild species, each with its strengths and limitations.
Scientists from Fisheries and Oceans Canada published a scientific review of the current state of knowledge on the methodological approaches used to quantify the impacts of aquaculture farms on species diversity and macrofauna abundance patterns.
How do we measure the connections between aquaculture farms and wild species? This is where different monitoring methods come into play, where scientists become environmental impact “detectives.” There are various techniques, each with its strengths and weaknesses; here’s an overview:
- Visual Studies: Divers and underwater cameras provide snapshots of the farm’s surroundings, offering valuable information about species composition and abundance. However, their limited scope and the potential bias of the observer can present an incomplete picture.
- Acoustic Techniques: Sonars and echosounders scan larger areas, revealing the presence of fish and invertebrates that may evade visual observation. While powerful, these methods have difficulties identifying specific species and can be affected by environmental factors.
- Capture Techniques: Fishing gear like traps and nets directly sample the surrounding community, providing concrete data on species composition and size distribution. However, these methods can be invasive and harmful to the ecosystem.
- Fatty Acid and Stable Isotope Analysis: According to researchers, biochemical tracer methods, including stable isotope (SI) and fatty acid (FA) analyses, can be used to distinguish nuances in the food web structure in many benthic systems, especially when used together.
- Genetic Analysis: DNA or RNA analysis from environmental samples such as water or sediments can reveal the presence of specific species, even those not easily visible. This technique is particularly useful for cryptic or elusive creatures but requires specialized expertise and interpretation.
No technique is perfect; each has its limitations. Nets capture only those that come close, cameras have a limited field of view, markers can be costly, and models, are complex. The study provides more detailed information on the mentioned techniques.
What is the Best Solution?
“There are several limitations associated with the use of single-survey techniques to assess interactions between wild species and aquaculture. Developing a framework to assess the environmental impacts of aquaculture expansion can be a useful tool for marine spatial planning and balancing the need for conservation and food production,” report the scientists.
In this regard, collaboration is key. Combining different techniques, leveraging each one’s strengths, gives us a more complete and accurate picture of interactions.
For example, using cameras to observe behaviors, nets to quantify abundance, and genetic markers to track the origin of individuals.
Additionally, scientists indicate that “to effectively assess marine environments, the most appropriate approaches must be chosen. Emphasizing a multifaceted approach, evaluating aquaculture-ecosystem interactions using various sampling techniques, is important to better understand the role that an aquaculture site can play in the aquatic environment and the potential for far-field effects.”
“The design of studies with complementary approaches can help obtain robust data that can be used to better understand interactions between aquaculture and ecosystems and the underlying immediate mechanisms,” conclude the scientists.
This continuous monitoring not only allows us to care for the health of our oceans but also ensures the continuity of aquaculture itself. By understanding interactions, we can mitigate negative impacts and leverage the opportunities that coexistence provides, ensuring a future where aquaculture and the ecosystem dance to the same tune.
The study was funded by the Competitive Science Research Fund Program at Fisheries and Oceans Canada.
St Andrews Biological Station, Fisheries and Oceans Canada
St Andrews, New Brunswick, Canada.
Reference (open access)
English G, Lawrence MJ, McKindsey CW, et al. A review of data collection methods used to monitor the associations of wild species with marine aquaculture sites. Rev Aquac. 2024; 1-26. doi:10.1111/raq.12890