Dead fish

The "discarding" of fish by commercial fishermen is a term commonly used to describe the practice of throwing unwanted fish back into the sea -- usually dead.

Under the European Common Fisheries Policy (CFP) discards have historically taken place for three reasons. Firstly, fish are discarded if they are small and under the legal minimum size which fishermen are allowed to land for that species. Second, they are thrown back into the sea if a fisherman's annual quota for that species has already been reached, making it illegal to land it. Lastly, fish are dispensed with if they are of a species which has no commercial market value.

Thankfully, discarding fish will soon become a thing of the past after the UK Government secured a historic victory in Brussels to set firm dates to reform the EU Common Fisheries Policy and introduce a ban on the practice. Hence the wasteful practice of discarding edible fish stocks like herring and mackerel will end from January 2014. A ban for white fish stocks will begin in January 2016.

The legislation will undoubtedly save the lives of many thousands of fish. But what of the scavenging birds that follow the fishing vessels to help themselves to a free lunch? How will they be affected by the move?

That's exactly what Dr. Stephen C. Votier, an Associate Professor in Marine Ecology at the School of Marine Science and Engineering at Plymouth University  (Plymouth, UK) wanted to find out.  To do so, Dr. Votier and his team attached cameras and GPS systems to ten Northern Gannets (Morus bassanus) to provide a unique view of how the seabirds interacted with the fishing vessels.

Results from his research revealed that all the cameras on the birds captured images of large (>15m) boats, but not smaller vessels. Virtually all the vessels were trawlers, and the gannets were almost always accompanied by other scavenging birds. All the birds  exhibited an area-restricted search during foraging, but only 42 per cent of such searches were associated with the fishing vessels, indicating that the birds were still foraging naturally.

The research illustrates the fact that those vessels discarding fish provide an important source of food for foraging gannets, but that they will be able to adapt well if discards were to disappear altogether -- if there is sufficient food to meet their nutritional needs.

While Dr. Votier's research has provided a fascinating insight into the foraging habits of seabirds, his technique of equipping birds with cameras and GPS systems might also be used in the future to fight in the battle against illegal, unreported and unregulated fishing activity, which may still result in a significant amount of discards.

References:

1. A Bird’s Eye View of Discard Reforms: Bird-Borne Cameras Reveal Seabird/Fishery Interactions

2. Historic day as Fisheries Ministers agree a date for discards ban

Related articles from Vision Systems Design that you might also find of interest.

1. Cameras and computers count fish

Researchers at the University of Western Australia (Perth, Australia) led by associate professor Euan Harvey have been awarded a three-year, $450,000 Australian Research Council Linkage grant to develop a vision-based computer algorithm to count and measure fish.

2. Fish processed by vision system

Engineers at the Icelandic firm Valka (Kópavogur, Iceland) have designed a vision-based cutting machine that can cut out pin bones from red fish, as well as trim and portion the fish into fish fillets.

3. A fish tale

To maximize profits, fish farmers are using a machine-vision system and smart software to sort good fish eggs from bad.