CPUE, or Catch Per Unit Effort, is the main component of fishery stock assessments used by fisheries scientists. Put simply, CPUE indexes the outputs of a fishery (i.e. the catch of fish) over the inputs — such as the number of boats and the number of days spent fishing. With all things being equal (e.g. the same fishing effort using the same technology used the same way in the same area etc.), an increasing CPUE over time would mean a population of fish is increasing. A stable CPUE would mean the population of fish is being fished at its maximum sustainable yield (Fmsy) — that is the biomass is at a level that yields the maximum amount of fish to a fishery. If CPUE is decreasing this means the population of fish, all things being the same, is decreasing and is probably being overfished.
It is important to note here that a stable or increasing CPUE doesn’t necessarily mean a fishery is sustainable or responsible. To make such a claim you would need to know the CPUE for all the species being directly caught or killed in the process, and this could be for species like sea birds or turtles, or those indirectly and negatively impacted upon through habitat destruction or by simply interfering with their growth and/or reproductive output. Obviously it is responsible not to do this where you can, but even if a fishery has scientific evidence to show that it is sustainable on all these levels, it may not be considered responsible if, for example, slave or child labour had been used to catch, process, and/or distribute the fish to your supermarket shelf — even if it has an Eco-Label.
Despite it being of critical importance to have the CPUE data of the target species of a fishery, as well as the incidental catch, we don’t have enough of either to understand whether most stocks of fish are truly stable or not. And even though the number of species in the United Nations Food and Agriculture’s (FAO) database on fisheries statistics almost doubled between 1996 and 2013, the FAO also found that of the developing nations that produce around 90% of our seafood, less than 40% were submitting adequate data sets. This does not bode well when you consider that the same organization claims that up to 90% of the world’s seafood species are at maximum exploitation or on the verge of collapse.
So if CPUE data is so important why can’t we get enough of it? Well based on my experiences, fishermen do not like to tell anyone what fish they have caught and where — they simply don’t want others to know where the fish are so they don’t go and fish on “their grounds”. If anything they will tell you there were no fish where they caught them, or that they caught them somewhere they didn’t, or they will tell you the truth assuming you’ll think they are lying! They also don’t want to tell governments or NGOs. Neither of these two will help them catch more fish. All they can do is stop them from fishing through input controls (take back licenses, reduce their fishing days etc.), or lobby governments to take such actions. Another reason they don’t want to tell their government what they have caught is that they don’t want to pay tax.
Fisheries scientists are also often not trusted by fishermen. Indeed, some fishermen won’t give back the tags they find in fish that fisheries scientists put into fish to assess population size. This is because the more tag returns can mean the fish stock is smaller — I have seen fishermen collect tags as a demonstration of their defiance. Of course it is not all bad. With rights based fisheries management (RBFM), where the rights or ownership of the fish stock is awarded by the government to the fishermen, the relationships have become, dare I say it, almost amicable! However RBFM is the exception, not the norm, and most of the fishermen in the world see it as their right to fish without interference.
So how can we incentivise fishermen to provide their CPUE data? How can we do so and protect the data that fishermen consider sensitive? How do we get the data that fisheries scientists and governments need to assess fish stock size, better manage the stock, and make the move toward RBFM? Eachmile Technologies have embarked on an initiative called Fishcoin whereby fishermen are rewarded with Fishcoin tokens for inputing data into a decentralised application. The tokens will be exchanged for mobile tops ups or currency.
The fishermen are rewarded in tokens by the first receiver to start traceability through a supply chain, or by government with data collected on a anonymised basis, aggregated and communicated to government for stock assessment. The data could eventually be disaggregated and identities revealed when the fishermen and the government are ready to move to RBFM. With the knowledge they will transition to RBFM, fishermen could even be incentivised to tag and release fish, collect data, and become defacto fisheries scientists — imagine that!