Fish consumption by seabird

Fish consumption by seabird

Marine Pollution Bulletin Marine Pollution Bulletin, Vol. 15, No. 8, p. 312, 1984. Printed in Great Britain. Fish Consumption by Seabirds S/r, Animal...

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Marine Pollution Bulletin Marine Pollution Bulletin, Vol. 15, No. 8, p. 312, 1984. Printed in Great Britain.

Fish Consumption by Seabirds S/r, Animals may resort to a variety of devices to distract opponents. Thus cephalopods try to escape behind a cloud of ink, and their predators the fulmars expectorate a disgusting spray of half-digested material. Dr R. W. Furness resorts to a combination of these techniques when his calculations of the amount of fish birds eat are questioned (Mar. Pollut. Bull., 14, 2 9 4 - 2 9 6 ; 15, 2 4 4 248), and has put up a smoke-screen of dubious composition. It would be tedious to discuss it at length when I originally brought up many of the points covered and dealt with them again in my previous contribution, and he has become long-winded. May I merely point out that in fact he appears to accept that we still know far too little about such important factors as the range of the birds, what they eat, who their competitors are, and the movements of their prey, to come to any precise conclusions, and that these factors which have been glossed over introduce far laro'~r margins of error into his calculations than those which he discusses at such length? Without wishing to make any particular claims for my calculations, I should like to suggest that they must be at least equally reliable. Perhaps after considering this your readers may care to wonder whether they would be prepared to stake their reputations with such confidence on a statement that birds eat even 20% of the fish in an area where there has already been a confrontation over seals as established fact in such a place as Advances in Marine Biology (20,

Stabilizing Oily Waste Stabilisation of Oiled Beach Material. B. Waldie, C. S. Johnston and D. Haldane. Institute of Offshore Engineering, Heriot-Watt University, Edinburgh, 1984. 55 pp. Price £12.00. ISBN 0904046-11-7. This is the report of a research study carried out by the Institute of Offshore Engineering on behalf of the Department of the Environment as part of the government contribution to dealing with waste from major oil pollution incidents. The primary objectives were to assess the scope for using quicklime to stabilize oily waste so as to produce a material suitable for landfill or road construction purposes. To this end the permeability of stabilized material to water was tested, together with their mechanical strength. The idea of quicklime stabilization is hardly new and a good quarter of the report is devoted to reviewing French experience after the two main tanker incidents of Amoco Cadiz and Tanio. Efficient and controlled mixing of beach material and lime in correct proportions is not the 312

0025-326X/84 $3.00+0.00 Pergamon Press Ltd.

2 2 5 - 3 0 7 ) . Yet he originally made it 29%, and does not appear to dispute that if he had not downgraded his own census results without saying so, the figure would have been larger. As Admiral Beatty remarked about the battle-cruisers that blew up at Jutland, something appears to be wrong.

3 Countlaw Place, Milltimber, Aberdeen AB10DS, UK

W.R.P. BOURNE

Sir, I totally agree with Dr W. R. P. Bourne that we need more information on foraging by seabirds and on their food stocks, but he will see that I stated this in my 1978 paper (J. Anim. Ecol.). It is not a problem which he alone understands, but one which my paper specifically addressed by sensitivity and Monte Carlo analyses and discussion. H e should also appreciate that I was careful to point out the implication of this. I stated clearly that the estimated population energy requirement had a 95% confidence interval of + 50% of the mean. Those with an elementary understanding of statistics will appreciate this to show that the true value lies within a broad range centered on the mean estimate, which was 29%. I have never stated, as Dr Bourne suggests, that consumption by Foula seabirds is exactly 29%, but rather that it is of that order, and certainly greater than the one or two percent he seems, for no clear reasons, to expect.

Zoology Department, Glasgow University, Glasgow G12 8QQ, UK

R. W. FURNESS

least of the problems and dust generation can be serious in layering and pit mixing techniques. The authors suggest that the coarser grades of quicklime may therefore be preferable but it is perhaps worth remembering that a material comprised of very fine particles can be remarkably stable due to the cohesion between particles. Those who have prepared concrete mixtures of cement and sand in blustery weather can testify to this. With a cost of about £37.00 per tonne, alternatives to quicklime were also evaluated. Cement, pulverized fuel ash (P.F.A.), clay, micaceous waste and limestone powder were looked at but none of these offer an easier option: the cheaper materials are less effective in binding oil and in virtually all cases the transportation of materials will loom large in the cost equation. It is not easy to make the subject of oily waste disposal come to life but the authors would have had an easier task had they introduced the main 'players' somewhat earlier. The reader is well advised to look first at Section 7 which describes the vital statistics of the stabilizing materials.

T. H. MOLLER