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low at the present time, a low which has brought the fishery to its present
grave crisis.
b) This secular fluctuation corresponds to that which has occurred
in the same period in Portugal And from the general indications which we
have it would appear that the fishery in Spain has also had in the last
century an analogous progress down to the present low pointj from which
it has begun to recover only in the past two yearso

This fact is quite important for us because it can be interpreted
in the sense that the Mediterranean tuna fisheries are subject to the same
general influences which determine analogous fluctuations of great ampli-
tude in the Atlantic fisheries, and that therefore the Mediterranean
fisheries are subject to the oceanographic influence of the Atlantic,
which can only be manifested in the influx of water from the Atlantic
through the Strait of Gibraltaro

It is in fact not very probable, although still riot precluded, that
it is a question of influences of a meteorological or other nature,
operating synchronously but separately in the two regionso

This is one of the many cases which show how useful would be an
oceanographic observatory at the Strait of Gibraltar j, the idea of which
was suggested by Steuer, which would gather data for the study of the
relations between the two seas and of the seasonal and annual variations.

c) The secular fluctuation of the Lusitano-Mediterranean tuna
fisheries corresponds with the last secular fluctuation of the herring
fisheiy at BohuslSn , ^described by Pettersson and Johansen, except for a
lag of several years.

And I note that the existence of these fluctuations has been
recognized for many centuries now (Ljungman). Pettersson relates it
to secular variations in the tides (ill years). Storrow has also occupied
himself with the question, placing in evidence analogous fluctuations for
other fishes. It is admitted, in any case, that these phenomena are
provoked by changes which take place successively and alternately in the
physical conditions of the waters.

The analogy between the fluctuations of the Mediterranean tuna
fisheries and the herring fishery in the Skagerrak appears to conform very
well to the concept expressed above that our tuna fisheries reflect
Atlantic influences. And the proven antiquity of the phenomenon which
occurs in Scandinavia augments the probability that that of the tuna
fisheries has had a periodic character^

d) There are specific zones in which the overall effect of the
secondary fluctuationa of the tuna fisheries , at least those of a^ certain
Eimplitude , present a_ marked analogy. One of these zones embraces all of
Sardinia and Tunisia (Sicily with Favignana is separate from it although
very near).

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