pingers - HELCOM Meeting Portal

Dnr: 12-16-2006
2006-03-07
Trials with fishing nets equipped with 'pingers'
By-catch in fishing gear has been identified as the most serious current threat to the populations
of several cetacean species. The EU has introduced regulations designed to reduce the by-catch
of small cetaceans, using acoustic deterrent devices known as 'pingers'. Fishermen have
expressed concern about being required to use these devices as they are thought to involve extra
time and labour costs for the fishermen as well as additional capital outlay. Here we present the
results of sea trials carried out in January 2006, with the purpose of investigating how the use of
pingers will impinge in practice on the handling of nets on board Swedish fishing boats.
In anticipation of the coming into force of EU regulation 812/2004 on the 2004-06-01, the county
administration in Skåne commissioned the Swedish Board of Fisheries (Fiskeriverket) to carry out
a study into facilitating the introduction of the new requirements for the local fishing industry. The
main goal of the study was to collaborate with fishermen to identify what problems the use of
pingers was likely to give rise to, at the same time as experimenting with possible technical
solutions to suit the various fishing methods of the affected fisheries.
The new regulations, in brief, require that:
1. Pingers must be used on all boats of 12m length or more, when fishing with bottom-set gill
nets, tangle nets or drift nets in certain defined areas of the southern Baltic from 2005-0601 (Fig. 1).
2. In the Skagerrak and Kattegat sea areas (eastern North Sea), all boats of 12m length or
more must use pingers on bottom-set gill nets and tangle nets when the mesh size is
220mm or greater, or when the nets are shorter than 400m in length (between the 1st August
and the 31st October).
3. From 2006-01-01, five percent of the total fishing effort by boats of 15m length or more
using pelagic trawls in ICES areas IV, IIIa, IIIb, IIIc and IIId (only from June to September
in the latter case) shall be monitored by independent observers in order to estimate bycatches of small cetaceans.
4. From 2006-01-01, five percent of the total fishing effort by boats of 15m length or more
using bottom-set gill nets or tangle nets with a mesh size of 80mm or greater, in ICES sea
areas IIIb, IIIc and IIId, shall be monitored by independent observers in order to estimate
by-catches of small cetaceans.
5. The use of drift nets is to be progressively phased out and will be banned from the 1st
January 2008.
Acoustic deterrent devices for porpoises
There are today two basic types of pingers, digital and analogue, which differ both in the sound
frequency used and the signal strength. Two of each type are commercially available. According to
the EU-regulation, pingers are to be attached along the head rope with one at each end of the net
and at maximum spacings of 200m for digital and 100m for analogue devices. The types of pingers
currently on the market also differ greatly in characteristics such as ease of handling, life
expectancy, running costs and durability (see below).
Figure 1. Areas where boats ≥12m are required to use pingers on certain specified gear. ICES areas marked
with Roman figures.
Stake holder meeting
On the 30th September 2005, a meeting was held in which all the fishermen affected by the new
regulations were invited to meet with representatives of the relevant authorities. The purpose and
the significance of the EU regulations were explained and the implications for the fishing
community were discussed.
A number of practical problems which could possibly arise with the handling of pinger-equipped
gear were identified. These were to serve as a starting point for the present study and are listed
below.
1. In the Skåne and Blekinge net fisheries, nets are often set by means of a tube which guides
them from the pound and out over the stern of the boat. This tube is often angled as it
comes down to the net pound and may be provided with some form of funnel at the forward
end (Fig. 2). Fishing vessels would generally be travelling at about 6 knots while shooting
the nets. If a pinger was caught on the edge of the funnel or mouth of the tube and should
be torn off, this could constitute a serious safety hazard to any crew member standing
nearby.
2. The weight of a pinger can be between 230g and 410g. When using nets with large mesh
sizes, one could imagine a pinger slipping through the mesh of the underlying layer of net,
so that when the net was paid out, the pinger could drag with it a whole section of extra net
which would then get stuck in the net tube.
3. A lot of fishing now takes place using so-called floating line without floats. If pingers are
attached to this kind of net, instead of blending in with the floats, they will stand out from
the fabric of the net. The problem with this is that these types of nets are often handled with
specialized equipment which is not designed to tolerate the presence of floats or float-like
pingers. For example, in Öresund and down as far as Trelleborg there is a problem with
excessive seaweed getting caught in the nets. Fishermen have to clean the nets periodically
and for this they use a special grid of heavy wires suspended in a frame; the net is passed
between the wires while being shoot at a speed of 5-6 knots, which shakes and scrapes the
weed from the net.
4. A similar misgiving was suggested in regard to another type of net cleaner which is used in
a number of harbors. With this machine, the nets are drawn through metal loops attached to
arms which move up and down, thus shaking off any weed. The expectation was that
pingers would not pass easily through these loops.
5. The question also arose as to whether nets equipped with pingers could pass through net
flaking machines (normally Bebbnik). These are used to over-end the nets when the headrope and the bottom-rope has got twisted. They are also used by many fishermen to clean
the nets of seaweed.
Previous studies and trials
Two recently released reports present the results of comprehensive sea trials of four commercially
available porpoise pingers now on the market, one from Ireland (Cosgrove et al., 2005) and one
from the UK (Anon, 2005). The trials investigated the ease of handling of the pingers as well as to
some extent their battery life and general durability in actual fishing operations. Both studies
focused mainly on bottom-set gill nets, although smaller-scale trials were also carried out using
tangle netting and trammel nets. A summary of their conclusions is given below.
Four types of pingers
Fumunda (Fig. 3d)
Fumunda pingers were seen as the easiest to attach to the nets (Cosgrove et al., 2005; Anon, 2005).
This was because they taper sharply at both ends and also have an eyelet right at the tips, which
allows them to be lashed very tightly to the head-rope. This prevents them from getting caught on
anything and reduces the risk of them slipping through the weave of the net itself. These pingers
also worked smoothly in the haulers, net flaking machines and other deck equipment. Nets
equipped with Fumunda pingers were also no harder to set than normal nets; this was due to their
small size, low weight (230g) and tapered profiles.
These pingers were also resistant to wear and tear and to physical damage. An unpublished Danish
trial (Krog, pers. com.) found that they had the greatest tensile strength of the four pingers tested.
Cosgrove et al. (2005) found however that the battery springs were too weak, with the result that
after the trial nets had been set 28 times, 3 out of 15 pingers were no longer working. The
manufacturer has since taken care of this and stronger springs are now being used. Anon (2005),
meanwhile, found that the battery life was less than 6 months. The high power consumption was
shown to be due to an amplifier which had been incorporated into the pingers to give a greater
effective range. The manufacturer has removed the amplifier from the latest model in order to
prolong battery life. Preliminary tests of this model indicate a battery life of 19 months assuming
that the pingers are permanently switched on.
Figure 2. Example of a net tube on a fishing boat with a wheelhouse at the stern.
The net is paid out from the net pound in front of the wheelhouse, through the tube over the
wheelhouse and out over the stern.
Fumunda is equipped with a salt water sensor to switch off the pingers when not submersed but
since it is damp enough in the stored nets many pingers continue to transmit. Batteries can be
replaced, but this has to be carried out under dry conditions as the electronics inside must not get
wet, which in turn involves extra work.
The Fumunda pinger operates at 10 KHz and is thus within the normal range of human hearing.
This means that when the boat is at the quayside and the engines are not running, the noise can be
disturbing. On the other hand, it also means that it is easy to check whether the pingers are
working or not without any extra equipment. However, older people may still find it hard to hear
10 KHz pingers.
AQUAmark 100 (Fig. 3c)
The AQUAmark pinger is significantly heavier (410g) and somewhat bulkier than the Fumunda,
which makes it harder to pass through the net flaking machine. It was also considered to be harder
to attach to the net, due to its extra girth making it harder to lash snugly to the head-rope. Thus
when the head-rope is tightened, the knots holding the pingers tend to work loose. Also the eyelets
for attaching ropes are not right at the tips (as on the Fumunda), which means that the ends can get
caught in the net mesh, depending on how the pingers are tied on (see below under Swedish trials).
The weight of the pingers was also perceived as a safety risk on certain boats.
Figure 3. Four types of pingers: (a) Savewave; (b) Airmar; (c) AQUAmark 100; (d) Fumunda. Cosgrove et
al. (2005).
AQUAmark pingers seem to be equally sturdy overall as the Fumunda ones. In the Irish trials, 1
out of 15 pingers failed to work after 14 fishing trials with bottom-set gills nets, while 6 out of 13
were out of action after shooting tangle nets 17 times (Cosgrove et al., 2005). This was due to a
faulty casting which allowed water to leak into the casings. This has now been rectified by the
manufacturers.
The battery life on the AQUAmark is said to be 1½ to 2 years. The batteries cannot be changed on
this pinger; the whole pinger has to be replaced, which naturally increases the running costs. All
trials so far suggest that the batteries' lifespan is significantly more than 12 months, but so far no
trials have gone on long enough to verify the manufacturer's claims of 1½ to 2 years. One costsaving advantage of this model is that they are powerful enough to be placed at 200m spacings.
Airmar (Fig. 3b)
This pinger suffers from the same problems with mounting and safety as the AQUAmark pinger as
it is relatively heavy (410g) and more blunt-ended than the Fumunda and the AQUAmark.
Similarly it had the same tendency as the AQUAmark to work loose. An advantage is that the
batteries can be changed, but just like the Fumunda it has to be placed at 100m intervals so it takes
twice as many pingers as the AQUAmark according to the current EU-regulation.
All 15 Airmar pingers in the trials were still working after 14 fishing cycles. The batteries had
however been damaged from the impacts when the gear was shoot and after further use they
stopped working. As of the time of writing, this problem had not been solved. Unpublished tensile
strength tests from Denmark also showed that this pinger was the weakest and that it easily broke
apart at the attachment points (Krog, pers. com.).
Savewave (Fig. 3a)
This pinger was very hard to use in the trials because of its bulky and awkward shape. It easily got
stuck both in the hauler and the net flaking machine. It also broke easily. Every single Savewave
pinger failed during the trials.
Trials with trammel nets
Because of the large mesh sizes in trammel nets, the risk of pingers falling through the mesh and
getting themselves entangled in the net is increased. In Cosgrove et al. (2005) the results of fishing
trials of trammel nets equipped with pingers were presented. In the first trial, pingers were attached
without floats. Trammel nets have no floats on the head-rope, relying rather on their own
buoyancy and on the lift created by water movements. Pingers with no inherent buoyancy (i.e. all
the pingers tested) will therefore tend to fall to the bottom and get caught in the gear. Without
distinguishing between different types of pingers, or between shooting and hauling the nets, it was
observed that 34% of pingers became entangled at some point. This figure was reduced to 17% in
a second trial by attaching the pingers with a float either side and a net stocking around the whole
unit, as in Figure 4 below. This technique is incidentally very similar to that used in the Swedish
trials (see below).
Summary of results from other trials
The trials showed that overall the Fumunda was the pinger which most smoothly fitted into the
structure of the gear and which worked best in the deck machinery. This was because it was small,
light and fusiform. Another advantage is that one can change the batteries oneself.
Figure 4. Fumunda pinger mounted with a float either side and a net stocking around the
whole ensemble in order to reduce the risk of it falling through the net meshes. Cosgrove et al. (2005).
AQUAmark is on the whole a very robust pinger with a good service life. Its drawbacks are that it
is heavy, that it can't be fastened at the tips which makes it harder to fit snugly to the head-rope
and that the batteries cannot be changed. The other two types of pinger, Airmar and Savewave, still
have defects which have not been remedied and they cannot be recommended at the present time.
When it comes to trials with trammel nets, there were much greater problems with pingers getting
entangled. One problem that was apparent in all these trials was that the heavier the pinger was, the
more often it caused the net flaking machine to fail. The reason was that the weight of the pinger
prevented the flaking machine to over-end the net.
Operating costs
Operating costs for the various pingers were evaluated by Cosgrove et al. (2005). Table 1 shows a
re-worked version of the running costs calculated by Cosgrove et al. (2005) for the two most
promising pingers. The adjustments made were to update the prices to current prices and to update
the battery lifetimes. The table makes clear that operating costs between pingers differ appreciably.
There are no great differences between the frequency of servicing required (either replacing
batteries or replacing whole pingers), but since changing the batteries has to take place in a dry
space, this requires a lot of extra work with the Fumunda pingers. We have also assumed that 10%
of pingers will cease functioning after one year. Our estimates based on these assumptions, as
shown in the table, result in higher initial costs for the Fumunda, but it still comes out as the
cheaper option in total over the five year period. The high-frequency AQUAmark requires special
(and costly) instruments to check whether the pinger is still working, while the Fumunda does not.
So the labour costs for servicing also vary between the different pingers. For an account of labour
costs, see Cosgrove et al. (2005) och Anon (2005).
Table 1. Operating costs for pingers for 20km net for 5 years, for two types of pingers. Revised after
Cosgrove et al. (2005).
Battery life (months)
Battery replaceable
No. pingers required
Unit cost (€)
Estimated battery cost
(€)
AQUAmark 100
24*
No
100
76**
Not relevant
Fumunda
19*
Yes
200
43** (inkl battery)
4
No. of
Cost for
Cost
No. of
Cost for
Cost
fittings
replacements
fittings
replacements
(€)
(€)
End of year
Initial fitting (0)
7650
1
8740
1
1
0
0.1
765
0
0.1
860
2
6120
1
800
1
1660
3
0
0.1
765
800
1
1660
4
6120
1
800
1
1660
5
0
0.1
0
0
Total cost(€) & No.
19890
3.3
1530
11140
4.1
5840
fittings
Average annual cost (€)
4284
3396
* Life time according to manufacturer. (preliminary results presented in April 2006 suggest that the latest version
(January 2006) has a lifetime of at least 40 months continuous pinging which would substantially change the outcome
of these calculations )
** Prize cheapest possible
Swedish trials
Our trials mainly investigated the possible practical problems which were raised at the stake holder
meeting in September 2005. Due to lack of available time, we were limited to discussions with
fishermen and to very simple tests in which we examined the practical handling characteristics of
nets equipped with pingers. That is, we have not considered pinger robustness and lifetime. The
conclusions of the British and Irish studies led us to exclude the Airmar and Savewave models
from the Swedish trials. The present studies were therefore undertaken with the AQUAmark and
Fumunda pingers. Four different fishing boats tested the pingers in operation. One used an older
version of the AQUAmark over a period of several years, two tested the latest AQUAmark pingers
and one boat tested the Fumunda pingers. Three of the boats were around 12m length while the
fourth was 20m.
Mounting
AQUAmark pingers were mounted in several different ways. One method was to splice the pingers
into the head-rope so that they became an integral part of it (Fig. 5a-c). A second was to tie them to
the original head-rope (Fig. 5d and 6). Since the AQUAmark weighs 410g, it has to be mounted
with extra floats. These will act as buffers and will presumably reduce wear and tear on the
pingers. By mounting the floats either side of the pingers, one is also reducing the risk of the
pingers falling through the mesh when the net is in the net pound, as the floats and pingers together
form a more rigid unit (Fig. 5b-d).
Figure 5. Different ways of mounting the pingers which we tested. (a) AQUAmark without float . (b)
AQUAmark with a float on either side. By mounting floats next to the pingers, the pingers are protected and
the risk of them getting caught in the net mesh is reduced. (c) Pinger protected by floats and also with a
fine-mesh net stocking around the whole ensemble to further reduce the risk of it catching in the net. (d) A
variation with a pinger and one float, wrapped in fine-meshed net, which has been used for several years in
the Kattegatt.
One boat tested the different pinger mounting methods in Figures 5a-c. The trials with Method 5c,
where the pinger and float were wrapped in a fine-meshed net stocking, did not work very well, as
the material of the stocking was of heavier gauge and stiffer than the material of the net, so it
tended to catch in the net when it was in the net pound. However, method 5b, with a float either
side of the pinger and no stocking, worked without any problems.
Mounting the pingers as in 5a-c by splicing them into the head-rope has the advantage that the
ends of the pingers are in line with the head-rope, thus minimizing the risk of them catching on
something. One disadvantage, however, is that the whole drag on the net comes to act on the
pingers. On boats with powerful haulers, there is a risk of tearing the pingers apart. Cosgrove et al.
(2005) report two instances where this did in fact happen during their trials (once with a Fumunda
and once with a Savewave). The tests carried out by Krogs (pers. com) showed however that the
Fumunda was the strongest of the four types of pingers and the AQUAmark the second strongest.
The pingers in Figure 5a-c were spliced into the head-rope at the net joins (where the individual
nets meet) along with the floats.
The crews on two of the boats tried instead mounting the pingers (AQUAmark and Fumunda)
along the head-rope (but still in the joins) as in Figure 6, and a third boat mounted the variant in
Figure 5d along the head-rope, as close to the head-rope as possible to reduce the risk of them
catching on something.
Shooting the nets
At the stake holder meeting, Swedish fishermen expressed unease over the possibility of pingers
catching on the edge of the net tube during the shooting operation, flying off and hitting a crew
member. Three boats have now been shooting nets with pingers attached, while traveling at speeds
between 4 and 6.5 knots. The nets were set either through a tube leading over the wheelhouse
(wheelhouse astern) (Fig. 2), or through a tube hanging over the net pounds (wheelhouse forward)
(Fig. 7) and out over the stern. The crews did not observe any tendency for the pingers either to get
stuck or to come loose and their judgment was that this is not a likely problem. Attempts were
even made to provoke an 'accident' by flicking the pingers to the side as they went into the tubes,
without success. On a fourth boat with a different deck setup (Fig. 8), the weight of the
AQUAmark pingers did lead to a safety risk. In this system the net is led to the stern via a net tube
along the side of the boat. Then the net comes out of the tube for a couple of metres until it passes
through another tube mounted in the middle of the stern railings, and so into the water.
Between the two tubes, a crew member stands and tries to straighten out the net when it comes
doubled out of the first tube. This person is therefore in the firing line if the net should get stuck
just when a heavy pinger is coming through the tube in front of him. This potential problem was
however solved by replacing the AQUAmark pingers with Fumunda ones, which only weigh half
as much. This crew has now fished with the Fumunda pingers attached and did not run into any
problems with net handling.
Another question mentioned above was whether pingers could slip through the net mesh when the
net was in the pounds and then drag a big bundle of net with them when the net was set. So far we
have been fixing pingers to cod nets and turbot nets (mesh sizes up to 260mm). The pingers have
been mounted as in Figures 5 and 6, in the joins between nets. With the turbot nets the pingers
were mounted as in Figure 5d.
Figure 6. Fumunda pinger mounted directly on the head-rope in a net splice. Photo Richard Caslake.
No tendency has been observed for the pingers to slip through the mesh or to drag extra net with
them during shooting operations. In some cases the net has been deliberately thrown into the
pound any old way without paying attention to the pingers, and still they did not get caught in the
net.
One type of gear which still gives cause for concern is trammel nets. These are presently used very
little in that part of the Swedish fisheries which is affected by the pinger regulations. However, it is
likely that entanglement problems would be more pronounced with trammel nets and it would
therefore be especially important to mount pingers in combination with floats to prevent them from
slipping though the mesh and to reduce hitching.
Hauling the nets
In the trials we used a Netop hauler with the AQUAmark pingers and a deep-water hauler with the
Fumunda pingers. In neither case did the pingers cause any problems.
Net flaking machine
Nets equipped with AQUAmark pingers were also put through a Bebbnik net flaking machine,
without any real difficulties arising. Occasionally the pingers were helped through by a crew
member giving a little extra tug on the net but this wasn't seen as a problem.
Figure 7. Net tube on a fishing boat with the wheelhouse forward.
Cleaning the nets
Net cleaning machines, such as the type with metal loops which shake the net as it is drawn
through the eyes, were not tested with pinger-equipped nets. However, the fishermen who
undertook the pinger trials did not think there should be any great problems with these.
There is however another type of net cleaner, which consists of about 5 very heavy wires
suspended horizontally in a frame (Fig. 9). The net to be cleaned is threaded through the wires
before shooting and which then proceeds at the normal speed of about 6 knots, pulling the nets
through the wires as it goes. It is not possible to pull a pinger through this type of net cleaner as
they are currently constructed. This type of net cleaner is used in Öresund and Trelleborg, where
there is a big problem with seaweed getting caught in the nets. It is at present used by only a few
boats (3 to 5 according to the information to hand), but they need to clean the nets several times a
week.
One solution to this problem might be to have the pingers with their float on a short line roughly as
in Figure 5b, attached with a karabiner. When shooting the nets one would hook the pingers on to
the head-rope after the net had passed through the cleaner. However this would mean stopping the
boat every time a pinger needed attaching and would be dangerous to do with a one-man crew.
Forthcoming Swedish trials
Fiskeriverket (Swedish Board of Fisheries) plans to carry out three further research projects in
connection with the new regulations. One is to investigate the propagation of sound waves from
pingers. The second is to study the distribution of porpoises along the coastlines of Blekinge and
southern Skåne, using hydrophones. The third is to investigate whether seals can learn to use
pingers to locate fishing gear. This could thereby increase by-catches of seals as well as damages
on catch and gear by seals.
Figure 8. Net tube with a gap on a 20m fishing boat. The net is lead astern through the net tube, emerging
from the PVC sleeve. From here it runs to the short metal tube on the stern railings and thence into the
water (right of picture).
Summary
The skippers who have now tried nets fitted with pingers are agreed that in practical terms it works
fine to have pingers on the gear. One exception is with those boats which use the wire net
cleaners, and on those boats the use of pingers will certainly require changes in the way the nets
are set. Since every fishing boat is slightly different in its deck layout, the practical implications of
introducing pingers will vary from boat to boat. However, we have now used pinger-equipped gear
with all the most common types of deck layout and have found that it mostly works well, without
causing any additional work as regards the actual fishing operations. Of course it remains the case
that in other regards, such as fitting the pingers in the first place, checking they are working and
replacing defective ones, they do cause extra work.
Figure 9. Wire net cleaner. The net is first threaded up and down between the wires and then is set at a
speed of 6 knots, passing through the cleaner as it is paid out. In this way it is scraped and shaken clean of
seaweed.
Cosgrove et al. (2005) and Anon (2005) both reported entanglement problems when using pingers
on trammel nets. This should not be a major problem in the Swedish fisheries, however, as most
trammel nets here are used on boats under 12m length, which are not covered by the regulations.
References
Cosgrove R, D. Browne and S. Robson. 2005. Assessment of Acoustic Deterrent Devices in Irish
Gill Net and Tangle Net Fisheries. Bord Iascaigh Mhara (BIM), Irish Sea Fisheries Board,
Marine Technical Report : Project 05MT07. rfccastletownbere@bim.ie
Krog, C., ck@krogconsult.dk
Anon, 2005. Trial of acoustic deterrents ('porpoise pingers') for prevention of porpoise (Phocoena
phocoena) bycatch. Phase 2 and 3 Endurance and Tangle net Trial. Seafish Technology
Implementation Department. B. Lart, Sea fish Industry Authority, St Andrews Dock, Hull,
HU3 4QE. +44 1482 327837. W_Lart@Seafish.co.uk