The effects of fishing on non-target species and habitats:
biological, conservation and socio-economic issues
M.J. Kaiser
School of Ocean Sciences, University of Wales-Bangor, United Kingdom
S.J. de Groot
Netherlands Institute for Fisheries Research (RIVO-DLO), IJmuiden, The Netherlands
The effects of fishing on non-target species and habitats: biological, conservation and socio-economic issues
Available from Blackwell Science in late 1999.
Introduction
Distribution of fishing effort and physical interaction with the seabed
1. Spatial and temporal patterns in North Sea fishing effort
S. JENNINGS, K.J. WARR, S.P.R. GREENSTREET and A.J.R. COTTER
2. Physical impact of beam trawls on seabed sediments
R. FONTEYNE
3. Is bottom trawling partly responsible for the regression of Posidonia oceanica meadows in the Mediterranean Sea?
G.D. ARDIZZONE, P. TUCCI, A. SOMASCHINI and A. BELLUSCIO
Effects of fishing on benthic fauna and habitats
4. Fishing mortality of populations of megafauna in sandy sediments
M.J.N. BERGMAN and J.W. van SANTBRINK
5. Short to medium term effects of otter trawling on the benthos and environment in muddy sediments
B. BALL, B. MUNDAY and I. TUCK
6. The effects of scallop dredging on gravely seabed communities
C. BRADSHAW, L.O. VEALE, A.S. HILL and A.R. BRAND
7. Impacts of scallop dredging on maerl grounds
J.M. Hall-Spencer and P.G. Moore
Fishing as a source of energy subsidies
8. The behavioural response of benthic scavengers to otter trawling disturbance in the Mediterranean
M. DEMESTRE, P. SÁNCHEZ and M.J. KAISER
9. Food subsidies generated by the beam trawl fishery in the southern North Sea
M. FONDS and S. GROENEWOLD
10. Impact of trawling on populations of the invertebrate scavenger Asterias rubens
K. RAMSAY, M.J. KAISER, A.D. RIJNSDORP, J. CRAEYMEERSCH and J. ELLIS
11. Seabirds and commercial fisheries: population trends of piscivorous seabirds explained?
C.J. CAMPHUYSEN and S. GARTHE
Long-term changes associated with fishing
12. Distribution of macrofauna in relation to the micro-distribution of trawling effort
J.A. CRAEYMEERSCH, G.J. PIET, A.D. RIJNSDORP & J. BUIJS
13. Long-term changes in North Sea benthos: discerning the role of fisheries
C.L.J. FRID and R.A. CLARK
14. Effects of fishing on non-target fish species
S.P.R. GREENSTREET and S.I. ROGERS
15. Impacts of fishing on diversity: from pattern to process
S. JENNINGS and J.D. REYNOLDS
Conservation methods, issues and implications for biodiversity
16. Technical modifications to reduce the bycatches and impacts of bottom-fishing gears
B. VAN MARLEN
17. Fishing and cetacean bycatch
N.J.C. TREGENZA
18. Effects of fishing on non-target species and habitats: identifying key nature conservation issues
M.L. TASKER, P.A. KNAPMAN and D. LAFFOLEY
19. The need for closed areas as conservation tools
H.J. LINDEBOOM
20. No-take zones: a management context
J.W. HORWOOD
Socio-economic implications and mechanisms for reducing fisheries impacts
21. Economic incentives to discard bycatch in unregulated and ITQ fisheries
S. PASCOE
22. Options for the reduction of bycatches of harbour porpoises (Phocoena phocoena) in the North Sea
J.M. McGLADE and K. METUZALS
23. Economic and socio-cultural priorities for marine conservation
P.J.S. JONES
24. Integrated management: the implications of an ecosystem approach to fisheries management
D. SYMES
Workshop conclusions
25. The implications of the effects of fishing on non-target species and habitats
M.J. KAISER
26. Glossary
Introduction
The impacts of human harvesting of marine organisms are manifested throughout the world and are most clearly seen in the resultant decreases in the population sizes of target species. Not surprisingly, this has led to concerted attempts to manage or sustain populations of commercially valuable species on which many local economies depend. Until recently, this preoccupation has deflected the majority of fisheries related research towards improving management of the stocks of target species. The wider effects of fishing activities on marine ecosystems were eluded to prior to this century (de Groot 1984), but it wasn’t until 1955 that Michael Graham undertook the first scientific assessment of the likely effects of fishing on non-target species. Graham’s paper summarily dismissed the possibility that fishing could adversely affect seabed communities and probably precluded any further research in this area for a further 15 years (Graham 1955). Preliminary studies of the effects of bottom trawls on the seabed and its fauna were published in a number of International Council for the Exploration of the Sea papers in the early 1970s (see de Groot 1984 for review). However, these studies did not progress much further beyond quantifying by-catch organisms in trawl catches and the depth to which trawl gears penetrated the seabed. Once again, this issue did not attract sufficient attention to maintain its research momentum. Finally, in the 1980s, reports of the disappearance of once common structural biogenic reefs began to cause concern that fishing might have caused widespread alteration of the seabed and the wider marine ecosystem (Riesen & Reise 1982). Towards the end of the 1980s, it became clear that large-scale changes had occurred in the distribution and abundance of scavenging seabirds in the North Sea. Furthermore, it was suggested that discarding activities associated with trawling were the source of these population changes (Hudson & Furness 1988; Furness et al. 1988, 1992). Since these findings were reported, research interest in the ecosystem effects of fishing activities has increased substantially worldwide and now encompasses effects on benthic biota, non-target fish species, marine reptiles, marine mammals and seabirds (Jennings & Kaiser 1998).
Europe has been a concentrated source of research initiatives that have addressed the ecosystem effects of fishing on the marine environment for the last two decades. Hence we considered it appropriate and timely to hold a workshop that gathered representatives of European research groups working on different aspects of this topic to update and review progress and future research needs. The structure of our meeting was biologically dominated. This was intentional as the biology of the ecological processes that result from fishing form the baseline of facts against which additional concerns, such as methods to reduce fishing impacts, socio-economic and legalistic issues, can be assessed. In addition, while those from the social sciences have had to dip into the world of biology to understand the rationale behind conservation issues and their implications, biologists often are unaware of the feasibility or ramifications of the recommendations that emanate from their research.
The book is divided into distinct themes. The first theme describes the distribution of bottom fishing disturbance and the direct physical process of sediment modification and the possible biological consequences of increased sediment resuspension (Jennings et al.; Fonteyne; Ardizzonne et al.). The second theme focuses on the direct effects of fishing on benthic fauna and a variety of habitats that vary in their stability and sensitivity to disturbance (Bergman & van Santbrink; Ball et al.; Bradshaw et al.; Hall-Spencer & Moore). The next theme considers the ecological consequences of redirecting energy in the marine ecosystem either by discarding material at the surface of the sea or through the animals and plants killed directly on the seabed (Demestre et al.; Fonds & Groenwold; Ramsay et al.; Camphuysen & Garthe). The long-term consequences of the quantifiable short-term effects of fishing (Themes 1,2, and 3) are investigated in the fourth theme (Craeymeersch et al.; Frid & Clark; Greenstreet & Rogers; Jennings & Reynolds). Then, consideration is given to important conservation issues (Theme 5) such as those species vulnerable to the effects of fishing outwith the target species and the importance of adopting an ecosystem approach to management of the marine environment. Methods for reducing the impacts of fishing for target, non-target species and habitats are also investigated (van Marlen; Tregenza; Tasker et al.; Lindeboom; Horwood). Finally, the economic incentives for improving fishing practice, the priorities that society attaches to conservation of the marine habitat and the reality of trying to implement ecosystem approaches to fisheries management are explored (Pascoe; McGlade & Metuzals; Jones; Symes).
These themes are brought together in a final concluding chapter that distills and integrates the major points that emerge from each study. Throughout the text, the reader will find reports of similar research findings and conclusions expressed by authors from a wide range of institutes with different professional backgrounds. This is a source of great encouragement, as it gives one confidence in the reported results and trends and that the opinions expressed are not merely emotive outbursts, rather that they are founded on well conducted science that addresses an increasingly important ecological issue.
Michel J. Kaiser
Bas de Groot