What is Sustainably caught fish?
For those who saw the Seaspiracy documentary, it was a question that a few of their interviewees struggled with!
Generally, sustainable fishing is where the level of fishing doesn’t reduce the population of fish stocks over time – what is taken is replaced naturally. Makes sense, right?
Stricter definitions are harder to come by because it really depends on how the existing fish stocks are measured. For example, when fishing for Cod, do you just measure the total Cod stock, or do you measure the effect on the total fish stock including all species? How is bycatch taken into account? How is the particular fishing method taken into account? It gets complicated quite quickly as the Wikipedia page for sustainable fishing demonstrates.
Ray Hilborn said, “To a great extent, sustainability is like good art, it is hard to describe but we know it when we see it.”
What is for certain is that the world as a whole is not getting this right. According to the WWF  40% of all fish caught is bycatch. As of 2015, 60% of fisheries are fully exploited, leaving no room for our ever-expanding global population, and 33% are overexploited .
The answer to the question really depends on who you ask. Is anyone fishing in the way you or I would consider sustainable? That’s a much harder question to answer, but for most types of seafood it’s likely to be no. If you are going to eat fish, then the best thing you can do is consult your local sustainable fishing guide but be aware that their idea of sustainable might not quite be what yours is!
Note: If you live in the UK you can consult the Marine Conservation Society’s Good Fish Guide, although you’ll find that most seafood has more than one rating, depending on where it is caught. They explain how their rating system works and it is interesting to note that they do take account of bycatch.
 “Defining and estimating global marine fisheries bycatch”, DAVIES RWD, et al., Marine Policy (2009), doi:10.1016/j.marpol.2009.01.003
 “The State of World Fisheries and Aquaculture “, Food and Agriculture Organization of the United Nations (FAO),