Examination of Witness (Questions 60-79)
3 NOVEMBER 2003
MR NICHOLAS
TREGENZA
Q60 Alan Simpson: In terms of cost-effectiveness
on this, and given there is a great deal of uncertainty as to
what it is that causes cetaceans to be able to swim comfortably
without getting caught and other cetaceans to get caught, if we
do not know the answer to that, are you confident in your own
mind at this stage, in terms of what we need to do, that there
is a compelling case for pingers, as opposed to different types
of break netting?
Mr Tregenza: That idea of lower-strength
net has not really been researched yet. You might find it worked
for the animals but the fish catch went down or the nets had to
be replaced every six months, so really it has to go through the
whole cycle of build them and put them into fishery trials, which
is quite a slow process. I think at the moment pingers are the
only thing we can see that can reduce the by-catch.
Q61 Mr Wiggin: We have talked all
about netting, and I buy dolphin-friendly tuna, which is hook-caught,
as I understand it. We do not have any of that in the UK, do we,
and are there any casualties that come from hook-caught fish,
particularly tuna, of cetaceans?
Mr Tregenza: Very few. Line-catching
methods generally are much more cetacean-friendly. It is not true
the other way round. In different parts of the world, dolphins
are stealing off lines, and that is becoming a major problem and
then fishermen start shooting them, and so on.
Q62 Mr Mitchell: Did I hear you say
that the cetacean switches off its own sonar?
Mr Tregenza: Yes.
Q63 Mr Mitchell: What is it doing,
is it just having a nap?
Mr Tregenza: No, it is going around
just listening to all the sounds, instead of listening to the
echoes.
Q64 Mr Mitchell: It is receiving,
not transmitting?
Mr Tregenza: Yes.
Q65 Mr Mitchell: Is this for long
periods?
Mr Tregenza: We do not know, because
the sound is in a very narrow beam. You put something in the water,
if you cannot hear them you think, "This beam is probably
shining just past my equipment." We have very little idea
about how much time they have their own sonar off.
Q66 Mr Mitchell: It is not running
down its own internal batteries, or wasting them?
Mr Tregenza: Yes, it is energy-costly
for the animal to use its sonar, so it has got an incentive to
go silent at times.
Q67 Mr Lazarowicz: In your written
evidence, you emphasise that, to quote you: "The current
generalisation, from a small data set, that it is only the bass
fishery [that is responsible for dolphin by-catch] is unreliable."
I think you are of the view that the cause of cetacean by-catch
will differ from year to year, depending upon a number of circumstances.
Am I correct in thinking that is your view?
Mr Tregenza: Yes.
Q68 Mr Lazarowicz: The information
from the observers that Defra put on the UK vessels, from a total
of 190 days at sea, covering a large range of fisheries, came
up with the conclusion that it was only the bass fishery that
had a problem with the cetacean by-catch. How is it that you have
a different view of the cause of the problem?
Mr Tregenza: I do not think they
have got it wrong. I think they are right in those few years,
but this by-catch in the mid-water trawl fisheries varies a lot
from year to year, and [referring to a graph] that is the sort
of annual dolphin strandings, and this big peak in 1991-92 a lot
of those had autopsies and they had mackerel in their stomachs.
I think, at that time, they were feeding mainly on mackerel. In
the study that I ran with French, Dutch and Irish colleagues on
mid-water trawls, we had by-catch in trawls that were catching
mackerel, they were set for horse mackerel, actually they were
catching mackerel. In fact, those Dutch boats, whenever they were
seeing dolphins and catching mackerel they were also catching
dolphins. One of the things I have learned, studying this, is
one year is not the same as the next, and in the pelagic trawl
fishery is particularly true. I think it is essential that observers
go on more than just the bass fishery, because they will find
a different pattern in some years.
Q69 Mr Lazarowicz: Do you think we
have the evidence to suggest which particular range of fisheries
might be responsible for by-catch on a more longer-term basis
than on the evidence of recent years?
Mr Tregenza: We have got some.
In the study that I referred to, the bio-eco study, there were
quite a lot of mid-water trawl fisheries west of Brittany that
were catching dolphins, and they have had huge strandings there,
600 or 700 animals coming in, in two or three weeks, twice since
1989, and these do seem to be mid-water trawl strandings. Really,
this problem exists all the way up the west coast of Europe, it
is not just the bass fishery here.
Q70 Mr Lazarowicz: I was going to
ask on that point, because some of the other evidence we have
had certainly points to historic problems in the North Sea fishery,
off the Western Isles of Scotland, for example. Within the UK's
waters, which particular areas do you think should be regarded
as the main source of the problem at the moment?
Mr Tregenza: The bass fishery
definitely has got to be top of the list.
Q71 Mr Lazarowicz: It is right to
focus on the South West of England fishery, as the main source
of the problem at the moment?
Mr Tregenza: For common dolphins,
yes. For porpoises, it is both really, the Celtic and North Seas.
Q72 Mr Lazarowicz: You were suggesting,
if I heard you correctly, earlier on, that the use of pingers
will be compulsory on all UK inshore and midshore fisheries, is
that correct?
Mr Tregenza: Yes. That is to deal
with the porpoise by-catch, that is a much more widespread problem.
It produces far fewer animals on the beaches and does not attract
so much media attention, but it is probably rather more serious
than the common dolphin by-catch in mid-water trawls.
Q73 Mr Lazarowicz: Which fishery
would you consider to be responsible for the by-catch when it
comes to the porpoise species?
Mr Tregenza: Really, all the fisheries
that use nylon, whether it is hake nets or tangle nets, they do
catch them. Mr Muirhead's idea of a net that the animal bounces
off does not actually work terribly well in practice, and really
they all do seem to catch them.
Q74 Mr Lazarowicz: From a policy
point of view, do you want to concentrate on the dolphin, that
we should be looking at the by-catch much more widely?
Mr Tregenza: Yes, but the measures
required are so different. Pingers do not work on the trawl fisheries,
they work only for the porpoise by-catch in nets, so I think separate
measures have to be introduced to deal with those problems.
Q75 Mr Mitchell: Just a final word
about separator grids, in the Defra strategy document; can you
explain briefly how it works? Is there a kind of hole in the net
that they can escape from, or is it not a powerful net?
Mr Tregenza: This is in the mid-water
trawl fishery, so they are towing an enormous cone of net to concentrate
the fish, then they have a cylindrical net in which the fish are
finally captured. In the front of that cylinder they put this
sloping grid, with a flap over the top, so the dolphin can go
up the grid and out through the top of the net.
Q76 Mr Mitchell: Right; so can the
fish, of course?
Mr Tregenza: They can, but they
do not.
Q77 Diana Organ: How does the dolphin
know that is the flap that lets him out? I am looking at this
diagram, and I could not work out why all the fish could not escape,
and who had taught the dolphin that you have to go in and then
you come up and you go out that way?
Mr Tregenza: It is searching.
The flap actually is weighted down slightly, so it does stay closed
and the fish cannot really push it open, but the presumption is
that the dolphin does push it open. I was very sceptical that
this would work.
Q78 Mr Wiggin: Is this not to do
with the fact that the dolphin has to breathe air, and therefore
the dolphin needs to go up whereas other fish do not need to escape?
Mr Tregenza: Yes, that is a good
point. The dolphin has a bias towards going up because that is
where the air is. Thank you.
Q79 Mr Mitchell: You are not enthusiastic
about them?
Mr Tregenza: I think the initial
results are very encouraging, but every gambler is encouraged
by the first break in a run of bad luck.
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