Download Plankton and Fisheries in Devon

Plankton and Fisheries in Devon
J. A. Lindley
Sir Alister Hardy Foundation for Ocean Science, Tha Laboratory, Citadel Hill, Plymouth PL1 2PB
Extended Abstract
Plankton, consisting of mostly microscopic plants (phytoplankton, Figure 1) and
animals (zooplankton, Figure 2) ranging in size from microscopic single celled
animals to jellyfish, which may be very large, but including the larval stages of fish
and shellfish as well as other bottom living and sea shore animals. The smaller
plankton is the base of the food chain in the open sea on which fish, marine mammals,
sea birds and the fishing industry all depend. Although the phytoplankton are the basis
of nearly all life in the sea they include species that can be toxic to animal life and
others that can clog nets or produce unsightly slime or foam that is unwelcome to
recreational use of coastal waters. The composition and quantity of the plankton
varies seasonally and from year to year and the success of fish stocks can depend on
the plankton being in the right place at the right time.
Figure 1. Phytoplankton (diatoms and dinoflagellates) and tinitinids (ciliate protozoans with bell
shaped cases).
Figure 2. Zooplankton, including copepod and cladoceran crustaceans, coelenterates and larvae of
several types of bottom living animals.
The fishing industry in Devon has experienced the consequences of environmental
variation in the past. A fishery for herring declined in the 1930s and from 1935
pilchard seemed to take the place of herring but after 1965 there was a return to the
conditions of the early 1920s (Figure 3). These changes were accompanied by
changes in the plankton indicating that the cause was climatic. Some recent results
from the Continuous Plankton Recorder survey (Figure 4) show that climate driven
changes are altering the plankton of the seas off Devon. Since the late 1970s to early
1980s there has been a steady warming of the seas around Britain (Figure 5) and the
species typical of warm temperate seas have increased in abundance and spead
northward while cold water species have declined. Many of our traditionally
important fish will decline if the present conditions persist and may disappear from
our waters if the warming trend continues. In contrast some commercially exploited
species, such as the red mullet and the spider crab are increasing.
Figure 3. Changes to the fishery off Plymouth from Russell et al. 1971.
Figure 4. Sampling by the Continuous Plankton Recorder Survey, 1946-2002.
Northern Hemisphere Temperatures
0.8
Deviation (°C)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
1850
1870
1890
1910
1930
1950
1970
1990
2010
Figure 5. Northern Hemisphere Temperature 1856-2003 (from CRU, University of East Anglia). The
arrows indicate the period covered by the “Russell cycle”.
References and further reading.
Beaugrand, G., Reid, P.C., Ibanez, F., Lindley, J.A. & Edwards, M. 2002.
Reorganisation of North Atlantic marine copepod biodiversity and climate. Science,
296, 1692-1694.
Beaugrand, G., Brander, K.M., Lindley, J.A., Sami Souissi & Reid, P.C. 2003.
Plankton effect on cod recruitment in North Sea. Nature, 426, 661-664.
Edwards, M.; John, A.W.G.; Johns, D.G.; Reid, P.C. 2001. Case history and
persistance of the non-indigenous diatom Coscinodiscus wailesii in the north-east
Atlantic. Journal of the Marine Biological Association of the United Kingdom, 81,
207-211, 2001
Edwards, M. & Richardson, A.J. 2004. Impacts of climate change on marine trophic
phenology and trophic mismatch. Nature, 430, 881-884.
Reid, P.C., Colebrook, J.M., Matthews, J.B.L. & Aiken,J. 2003. The Continuous
Plankton Recorder: concepts and history, from Plankton Indicator to undulating
recorders. Progess in Oceanography, 58, 117-173.
Hardy, A.C. 1956. The open sea, its natural history. Part I: The world of plankton.
London: Collins pp 335.
Hardy, A.C. 1959. The open sea, its natural history. Part I: Fish and Fisheries with
chapters on whales, turtles and animals of the sea floor. London: Collins pp 322.
Newell, G.E.; Newell, R.C. Marine plankton: a practical guide. 5th edition. 244p.
London: Hutchinson, 1977.
Russell, F.S.; Southward, A.J.; Boalch, G.T.; Butler, E.I. 1971. Changes in biological
conditions in the English Channel off Plymouth during the last half century. Nature,
234, 468-470, 1971
Richardson, A.J. & Schoeman, D.S. 2004. Climate impact on plankton ecosystems in
the northeast Atlantic. Science, 305, 1609-1612.
Southward, A. J. 1961. The distribution of some plankton animals in the English
Channel and western approaches. I. Samples taken with stramin nets in 1955 and
1967. Journal of the Marine Biological Association of the United Kingdom, 41, 17-35
Southward, A. J. 1962. The distribution of some plankton animals in the English
Channel and western approaches. II. Surveys with the Gulf III high-speed sampler,
1958-60. Journal of the Marine Biological Association of the United Kingdom, 42,
275-375.
Southward, A. J. 1963. The distribution of some plankton animals in the English
Channel and western approaches. III Theories about long-term biological changes,
including fish. Journal of the Marine Biological Association of the United Kingdom,
43, 1-29.
Useful web sites
DEFRA, Sea Fisheries Inspectorate and Coastal Fisheries Office
http://www.defra.gov.uk/corporate/contacts/sfi.htm
Hadley Centre for Climate Prediction and Research
http://www.met-office.gov.uk/research/hadleycentre/index.html
International Council for the Exploration of the Sea (ICES)
http://www.ices.dk/
Marine Biological Association of the United Kingdom.
http://www.mba.ac.uk/
Plymouth Marine Laboratory
http://www.pml.ac.uk/ (see http://www.pml.ac.uk/L4/ for plankton data off Plymouth.
Sir Alister Hardy Foundation for Ocean Science
http://www.sahfos.org/
University of East Angia, Climatic Research Unit.
http://www.cru.uea.ac.uk/
University of Exeter
http://www.ex.ac.uk/biology/research/groups/
University of Plymouth
http://www.plymouth.ac.uk/ particularly the Department of Biological Sciences