MARINE FINFISH AQUACULTURE, ANTIBIOTICS AND ESCAPED FISH: THE ELEPHANT IN THE ROOM

Introduction:

Climate change is profoundly affecting all facets of human activity. This affects worldwide aquaculture and could translate into an increase in the incidence of diseases that could be typical of warmer environments. The use of antibiotics to treat individuals in the culture may be associated with a risk (Dang et al. 2021). Extreme events can also occur as a result of this global change, leading to damage in facilities, breakage of networks and, consequently, escapes of individuals from aquaculture farms (Callaway et al. 2012). These escapees can be caught and misclassified as wild product by local fishermen and depending on the timing of the event, considerable amounts of antibiotics could reach consumers as a result (Figure 1). This review focuses on resilience techniques used to face possible harmful consequences derived from these events. We try to convey the need of a modern prevention and mitigation approaches to ensure safety for all consumers.

Materials and methods:

An initial set of searches using ISI Web of Science and Google Scholar catalogues were done between March & April 2021 using search strings aimed at different objectives. The first search string was aimed at identifying the current state of influence that climate change has on the aquaculture industry, as well as the relation between warmer temperatures, illnesses emergence and escape events. The second and third search strings were aimed at pre- and post-escape management measures and their current trends. Some publications missed by the initial search were provided by experts in the field or discovered by reading the full reference lists of all articles that provided relevant data, as well as review articles on related topics.

Results:

Proposals for prevention and mitigation were thoroughly examined and knowledge gaps identified.

> On the one hand, we compiled information and suggested improvement measures regarding current trends aimed at the decision-making process for the aquaculture facilities location. We also delved on the rationale of antibiotics use in cultured species and suggested alternatives with less associated risk, such as vaccination.

> On the other hand, we identified gaps in knowledge regarding the following:

• Development of management plans focused on the contingency of escaped specimens.
• Good practice manuals on culture management.
• Early detection measures.
• Preparation of recapture plans.
• Communication networks that notify local authorities about the escapees.
• Traceability of the amounts of antibiotics that reach local markets in the form of poorly labelled fish.

Conclusions:

This work showed the need for improvement in different areas aimed at avoiding unwanted quantities of antibiotics from reaching consumers. Regarding prevention work, a series of measures were suggested based on the data found. E.G.: while countries such as Norway are very experienced in implementing preventive vaccines others are still using large amounts of antibiotics with their cultures, showing a time lag relevant in our globalized world. Likewise, the fact of restructuring the data used in the site selection systems is necessary to incorporate useful information related to climate change that could lead to a full prediction model. Data conveying frequency of thermal anomalies could be an applicable example. Likewise, post-escape measures such as mitigation and management plans or the traceability of escaped fish likely to contain significant amounts of antibiotic must be improved to ensure the sale of a safe consumable product. Ultimately, only the combination of improved pre- and post- escape measures can minimally ensure a risk- free quality product.

References

-Callaway, R., A. P. Shinn, S. E. Grenfell, J. E. Bron, G. Burnell, E. J. Cook, M. Crumlish, S. Culloty, K. Davidson, R. P. J. A. C. M. Ellis and F. Ecosystems (2012). "Review of climate change impacts on marine aquaculture in the UK and Ireland."  22(3): 389-421.

-Dang, L. T., L.-H. T. Nguyen, V. T. Pham and H. T. T. Bui (2021). "Usage and knowledge of antibiotics of fish farmers in small-scale freshwater aquaculture in the Red River Delta, Vietnam." Aquaculture Research.

Funding:

This work is part of project GLORiA. GLORiA is supported by the Biodiversity Foundation of the Spanish Ministry for the Ecological Transition and Demographic Challenge, through the Pleamar programme and co-financed by the European Maritime and Fisheries Fund (EMFF). It is also part of the LIFE IP INTEMARES project "Integrated, innovative and participatory management of the Natura 2000 Network in the Spanish marine environment”.