Winners and losers under fishery pressure: a biological traits approach
Usually habitats are classified according to their species composition: burying shrimps in combination with brittle stars in deep muddy waters, shellfish beds in the coastal zone, etc. BENTHIS scientist Andrew Kenny has a different approach: seafloor animals can be described according to their traits, they effectively represent “little packages of traits” which interact with their surroundings in different ways. Some species live a short time, others a long time, some are weak, others strong, some small, others large, some like to scavenge, or filterfeed. By using the traits, he explores the effects that fisheries have on different habitats.
Kenny: “For example, we see an increase in scavengers, predators, free living swimmers, short lived and smaller sized animals with an increase in fishing pressure. But not all habitats appear to respond in the same way. The average size of animals appears to be most reduced when fishing occurs in coarse sediment.” His statements are not just based on a handful of samples. The samples data collated by the project partners amounts to more than 800 grab samples and 1000 trawls collected from the North Sea, Bay of Biscay, Norwegian Sea, Black Sea and Mediterranean. “For certain EUNIS habitat types bottom fisheries appear to cause an overall decline in the proportion of suspension feeders, such as the sand mason worm Lanice conchilega and changes are likely to have implications for the functioning of marine ecosystems.”
To perform the analyses, the scientists reclassified the macrobenthic data according to a set of 10 biological trait categories. In addition, they collated environmental data describing the physical attributes of the seafloor, such as sediment particle size, depth, nearbed shear stress. These data in combination with the traits and fishing pressure data allow different combinations of habitat type, fishing pressure and biological traits to be explored and assessed using multivariate statistical analyses.
“We are now working on defining more realistic habitat categories based upon observed environmental data rather than using the EUNIS habitat classes,” Kenny explains. “ We also intend to assess the impacts of different gear types in terms of swept area, and investigate the relationship between the traits and ecosystem functioning.”
