Epsilon Open Archive

This report is intended to throw light on the impact which the cormorant is having
on commercial fisheries, angling and fish farming in Swedish lakes and rivers, and
on small-scale inshore fisheries along the coast. Data for inland watercourses are
based on interviews with people active in each sector, while the marine fisheries
material is drawn from voluntary log-books kept by professional fishermen.
The Swedish cormorant population has increased in recent years, and with it concern
amongst commercial fishermen especially about a negative impact on the sector’s
profitability. Gillnets and fish traps have proved vulnerable to both catch losses and
gear damage. Fish pecked at by cormorants are usually unsalable. A complicating
factor which it is important to consider is that of hidden losses, due to either whole
fish being taken from the gear with no traces left behind, or fish (mainly eel) escaping
from the nets where cormorants have ripped the mesh.
In order to get a better idea of the impact of cormorants on the Swedish fishing industry,
we reviewed catch and gear data from the daily logs kept by professional inshore
fishermen as part of a voluntary co-operation with the Swedish Board of Fisheries,
using a sample of 44 log books for the year 2005 and 58 for 2006. In addition we
carried out telephone interviews with 40 professional lake fishermen in 2009. The
majority (85%) of lake fishermen reported catch damage due to cormorants, primarily
involving whitefish (Coregonus lavaretus) and vendace (Coregonus albula). Most
also claimed financial losses, though the extent of these were unclear. Generally
however, lake fishermen were more concerned (62,5%) about competition for the
resource, i.e. that the cormorants were reducing the stocks available to the industry.
One quarter of inshore fishermen reported cormorant damage, mainly in eel fyke
nets on the west coast and in the Baltic Sea bottom-set gill net fishery. The greatest
damage was experienced by the Baltic herring and whitefish fisheries. For a few
individual fishermen the losses were significant, but generally speaking they were
small compared with losses attributed to seal predation.
Lake fishermen estimated annual bycatches of on average just fewer than 20 cormorants
per fisherman, with a maximum of 30 birds. The voluntary log-books recorded
on average less than four bycaught cormorants annually per fisherman. However,
these figures are very much lower than those reported in a 2002 telephone survey of
inshore fishermen. To get more reliable bycatch data, we would need proper field
studies using onboard observers or camera systems.
Most of the fish farmers we interviewed saw cormorants regularly around their pens
but only one in four considered them to be a problem. More of them were concerned
about herons causing damage or taking fish.
Anglers fishing with rod and line in lakes and inland watercourses saw cormorants
as competitors, and they were also concerned about future stocks. However, many
felt that environmental degradation was more to blame than the cormorants for
weakened fish stocks.
As a general conclusion, most of the people interviewed considered that cormorants
are indeed responsible for direct damage to fishing gear and catches. The inshore
fishermen’s’ log-books show that at times there can be large catch losses due to cormorants,
but generally these are much smaller than losses due to seals. The interviews
revealed more concern overall about competition for resources than about direct
damage and losses. Demands for action from the authorities in the shape of culling or
egg pricking were a recurrent theme both in the interviews and in general contacts
with professional fishermen up and down the Swedish coast. At the moment we
have no clear data confirming that cormorants have a serious negative impact on
fishing stocks or on the ecosystem as a whole, but nor do we have any evidence to
the contrary. The fact that so many fishermen consider cormorants to be a threat to
their industry should in itself be a sufficient reason to take their concerns seriously,
until such time as clear evidence is produced that cormorants are in fact harmless.