Seabirds, marine mammals, seabed animals and other fish actually love human fishermen - because they throw back unwanted fish and that means free food with less work.

New rules have been put in place by the European Union's Common Fisheries Policy (CFP) bans throwing unwanted fish caught at sea back into the sea –  it forces vessels to haul fish to land anyway, which is a waste of time and money. The new CFP took effect on 1 January 2014 and will phase out the discarding of fish entirely by 2019. 

The goal is less waste. It's not a new issue. UK Parliamentary debates in the 1890s condemned the quantities of plaice thrown away by fishing fleets in the North Sea because they were too small to be sold.  The new policy adds this landing obligation and then gives an increase in quotas. It not only negates any conservation benefits, it hurts the environment, since the fuel to haul more fish adds to emissions.

A science approach would have been to change practices so that unwanted fish are no longer captured. But what about the scenario if the rules stay as is? It's hurting fishermen, and it isn't improving fish stocks, a University of Strathclyde report has found, but it will also hurt other marine life. It's simply a societal placebo for people who don't understand the food web.

So the paper already advocates reforms of a brand new policy. 

Professor Mike Heath
from the University of Strathclyde
 Department of Mathematics and Statistics said, "Wildlife everywhere capitalizes on waste from human activity, and discarded fish are food for a wide range of seabirds, marine mammals, seabed animals and other fish. Therefore, banning discards of fish could have unintended effects on the ecosystem."

Their computer simulation of the North Sea marine ecosystem investigated the effects of changes in the fishing pressure and the proportion of fishery catch which is discarded at sea. Forcing vessels to land fish which are currently discarded leads to adverse effects on seabirds and marine mammals – and on seabed animals – but without any improvements in fish stocks, the study found.

In contrast, changing fishing practices – so that unwanted fish are no longer captured – had dramatic effects in the model which affected the entire food web, with major benefits for birds, mammals, and fish stocks. This could be achieved by "improved selectivity", through the use of fishing gear designed to avoid unwanted catches and judicious timing and location of fishing.

Although both approaches to eliminating discarding satisfy the societal demand for reductions in waste of natural resources, the conservation benefits are quite different, the study authors found.

Dr. Robin Cook, who also worked on the research, said, "Our results highlight the importance of considering the broader ecosystem consequences of fishery management. Policy changes to reduce discards affect the food web and, without careful consideration, may dissipate or negate intended benefits.

"Inflating landing quotas to accommodate the entire catch is an inadequate solution with few conservation benefits. On the other hand, the effective reductions in harvest rates resulting from changes in fishing practices to eliminate the capture of unwanted fish can deliver conservation benefits, especially in heavily exploited systems.

"These ecological effects need to be considered alongside the practical, societal and economic issues in developing a sustainable policy."

Forcing improvements in the selectivity of fisheries by offering no compensation - which means being smarter about catching fish - keeps European newspapers from writing about wasted fished and has dramatic conservation benefits.

Published in Nature Communications