Recreational prawn drag netting in Far North Queensland

Transcription

Recreational
prawn drag netting
in Far North Queensland:
a destructive fishing
method when used in
fish nursery grounds
FIRST DRAFT ONLY
(a)
David C. Cook
Coastal Fisheries Specialist (Indo-pacific)
Member, Network for Sustainable Fishing
Douglas Region
Wonga Beach
Queensland, 4873
[email protected]
23 February, 2014
Recreational prawn drag netting in Far North Queensland: a destructive fishing method
when used in fish nursery grounds FIRST DRAFT(a) ONLY
The Network for Sustainable Fishing, Douglas Shire
The Network for Sustainable Fishing, Douglas Shire (NSF DS) is a network of individuals and
organisations promoting sustainable fishing practices in Far North Queensland for the benefit of local
communities. We see our role as assisting identify non-sustainable fishing practices in FNQ, bringing
them to the attention of the authorities and where action is deemed necessary, suggesting and
assisting create awareness of possible solutions.
Reports produced by NSF DR are available on the website of Fishers for Conservation at
www.ffc.org.au/Grey_Mackerel.html#latest. We have also started a Facebook page
http://www.facebook.com/SustainableFishing.
The background of NSF DS, with links to the science and management principles upon which NSF
conclusions and recommendations are reached, the content of relevant press items and our NSF
reports are summarised in our flagship documents: „A community campaign for sustainable
inshore fishing’ (2012) and „A review of concerns relating to the offshore gillnet fishery in the
inshore waters of the Great Barrier Reef Marine Park’ (2010). Both are available on the FFC
website.
Cover Photographs
(Top) Daintree Estuary:
 the river is just 120 km in length with a small, mostly rainforest catchment and small but
diverse areas of mangroves, suggesting:
 small nursery grounds for localised fish populations (of philopatric1 fish species) and
 ability to support only relatively small populations of large fish species in comparison to the
much larger rivers further south.
(Top left) Fatally meshed juvenile giant threadfins in prawn/bait drag net are a common occurrence.
(Mid. left) Section of a prawn drag net (bait net), red arrows indicate positions of fatally meshed
juvenile king threadfins, fairly representative of the remainder of the net.
(Bottom left) Sample of juvenile king threadfins which had been fatally meshed in a drag net
DISCLAIMER
This report is not part of any formal scientific study and is unfunded. It is prepared on a pro-bono basis for NSF
DS. Qualitative observations are presented to record personal observations and photographs taken during the
author‟s free time. The author has no vested interests in recording the observations contained in this report
other than furthering the cause of sustainable fishing and helping halt the observed and much reported decline
of important, iconic large inshore fish species in the area.
Being in possession of undersized regulated fish, whether dead or alive is an offence under the law. This greatly
reduces the opportunity for photography which must be undertaken when wet and dripping immediately after
hauling a net.
The intention of the report is to build awareness of the issue, to encourage formal investigation by the
authorities and to support any appropriate action which may be required.
It appears the stretch of beach where the observations were made may be a nursery ground hotspot for juvenile
fish of important regulated species.
It is recognized that insufficient research on the GBRMP‟s inshore fisheries has been undertaken by any party
into the effects of recreational prawn netting on our inshore fish stocks.
1
Species having non-mixing regional or local populations, in this case populations based only in and around connected
estuary systems. These are unlikely to be replaced by immigration from other distant and separate estuary systems if the
local stock is fished out.
THE NETWORK FOR SUSTAINABLE FISHING DOUGLAS SHIRE
23 February 2014
2
A 103 cm king threadfin caught by gillnet shortly after the opening of the 2014 barramundi season. Although it
has the potential to attain 1.7 m and 45 kg, the species is now rare at the above size in Douglas Shire, This fish
had developing roe when caught, indicating it was due to spawn probably in March or April. Traditional
spawning sites are located in or near estuaries in easily netted locations before and after the barramundi
closure (apparently depending upon region). They are philopatric (see footnote p. 2) and found either mostly or
exclusively in inshore waters. The species become females after eight years of age at 80 to 110 cm total length,
well above the minimum legal size of 60 cm. Although almost certainly required, there is no maximum legal size.
The biology of their juvenile stage is poorly known. There are insufficient checks and balances in place to
ensure capture rates do not exceed the production potentials of different local populations risking the extinction
of local stocks. The king threadfin is one of the species most likely to be vulnerable to growth overfishing by
regular drag netting for prawns in the Douglas Shire. It is also vulnerable to recruitment overfishing especially
where „out-of-town‟ offshore gillnetters and part-time gillnetters pulse-target spawning aggregations. When
2
reviewing catch data, the risk of hyperstability must be taken into account.
Contents
[Ctrl-click] to go direct to section or Plate required
Summary ............................................................................................................................................. 4
Background ......................................................................................................................................... 4
Aim & Methods .................................................................................................................................... 5
Results ................................................................................................................................................ 6
Discussion ........................................................................................................................................... 7
Conclusions......................................................................................................................................... 9
Plate 2: Wonga Beach prawn drag netting......................................................................................... 11
Plate 3: Examples of prawn drag net bycatch left on the beach, 11 January 2008............................. 12
Plate 4: More prawn drag net bycatch, 11 January 2008 ................................................................... 13
Plate 5: Crabs found in prawn drag net bycatch, 11 January 2008, at Wonga Beach ........................ 14
Plate 6: Juvenile barramundi are caught in prawn drag nets, also king threadfin. .............................. 14
Plate 7: Other species caught in 2014 by the author using a drag net ............................................... 15
Plate 8. “Gilling” “meshing” and entrapment in prawn drag nets ........................................................ 16
Appendix 1: The NSF DS recreational drag net poster ...................................................................... 17
2
„hyperstability’ is where catch rates stay high for some years whilst populations decline because very effective gear is
targeting schools or aggregations. The outcome is often a sudden population crash where local stocks may never recover.
This phenomenon often lulls fisheries managers, the industry and politicians into a false sense of confidence until the
unexpected crash, or in a multi-species fishery, just the disappearance of that particular species from the catch.
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Summary
In calm weather during the wet season fingerlings of large iconic inshore fish species such as king
threadfin and giant queenfish congregate in shallow water along beaches near estuaries in the
Douglas Shire of Far North Queensland. They feed on juvenile prawns which school in these shallow
waters at this time of year.
Every wet season recreational drag netting of these beaches by members of the public inevitably
causes the death of large quantities of juveniles fish, regardless of how much care is taken. This is
because the juvenile fish at this time are of sizes allowing them to become fatally meshed in the small
meshes of the drag nets. The majority of meshed juveniles die whilst restrained in this way or whilst
attempts are made to release them.
The Queensland fisheries regulations regarding the recreational use of drag nets are often flouted by
members of the public at such times who, in order not to risk losing prawns, often pull the net right out
of the water and attend to the prawns first. By this time the majority of juvenile fish in the haul are
already dead, even when not meshed.
This report presents observations on the species caught during a few short drags in the area over four
brief visits in early 2014. The composition of the juvenile commercial fish in the NSF poster,
photographed from discarded bycatch on Wonga Beach in 2008, is similar to those caught in 2014.
No attempt has been made to do a quantitative assessment of numbers of fish killed by dragnets.
Juveniles of one species said to have once featured commonly in drag net catches in the area, the
tripletail (Lobotes surinamensis) or jumping cod, is now very rare in the area. The author is not aware
of any being caught in drag nets in recent years.
The implications of the observed levels of mortality of juvenile fish and the need for appropriate action
are discussed. These observations and considerations may also be relevant to the use of commercial
bait nets and N11 nets in the Conservation Zones of the GBRMP, about which the author has heard
worrying reports but has no experience.
Background
The regulations regarding the use of recreational seine nets (commonly called drag nets) in tidal
waters are available from the Fisheries Queensland web site. The following are taken from this
source:
“Seine nets





Seine nets are commonly known as bait nets or drag nets in tidal waters.
A seine net must not exceed 16 m in length, 3 m in drop and must have a mesh size no greater
than 28 mm. The net must not contain a bag, pocket or similar device. The use of the net is
subject to the following conditions:
It must not be anchored, staked or fixed.
No part of the net containing fish must be out of the water other than to immediately remove fish
for release.
All regulated fish, and fish not intended to be taken, must be released into water deep enough
to allow the fish to escape.”
“... The possession or catch limits when netting for prawns is 10 litres per person.”
Prawn drag netting is conducted along the beaches of Pinnacle, Wonga, Newell, Cooya and Four Mile
in the Douglas Shire, mostly in the wet season after heavy rains. These are all beaches influenced by
nearby small estuaries. For years unrecorded numbers of people have targeted prawns along these
beaches during the wet season using what are commonly referred to as dragnets, (see Plate 2)
corresponding to the seine nets described above.
There are claims that some people illegally use double the legal length of drag net for greater
efficiency and some have been encountered using drag nets to intentionally capture and retain
undersized regulated fish for consumption. When challenged they have claimed to be unaware of the
law.
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More recently it appears that most prawn drag netting is done by day visitors from the Tablelands and
patrons of two local caravan parks that back onto Wonga and Pinnacle Beach. Opinion amongst most
beach residents appears to have swung against drag netting as a responsible fishing practice.
The best times for catching prawns are usually after the rivers have been in flood, when the inshore
waters are heavily discoloured, full of flood debris and the waves are small or the sea calm. This is
when juvenile fish of large species also congregate in the same shallows as the prawns.
Because prawns can escape if the net is left in the water whilst removing the catch, especially if there
are any waves, it is common practice to pull the net out of the water before removing the catch, thus
breaking the law. People often sort through the debris collected by the net to remove the prawns first
before attending to the fish. This is also illegal and the small fish trapped by the net, even if not
meshed, are often dead by the time the prawns are collected.
In nursery area hotspots such as some of these beaches would appear to be, large numbers of
juvenile fish of regulated fish species often become fatally meshed during the net dragging process,
having forced themselves so far through the mesh that they cannot be removed without fatally injuring
them (see Cover and Plates 2.3, 2.4, 7.1 and 8.1).
Fatal meshing occurs when the juvenile fish try to push head first through the mesh which slides over
the fins or gills which readily fold back flat along the body, before being unable to go any further and
becoming jammed in the mesh. When people try to remove the fish, the fins and gill covers open and
the mesh inevitably slips under them, as neither the fins nor the gills can fold backwards. The result is
that the small delicate fish can rarely be removed without serious injury. Sometimes people simply
pull the head off with a quick tug or break gill covers (see the juvenile grey mackerel with broken
operculum, Plate 3.4) as the quickest method of removing a tightly gilled small fish.
Some local residents, although still very concerned over the needless waste of young fish, no longer
bother to phone the Fisheries patrol office as they consider nothing will be, or can be done to
apprehend those breaking the law. They state that they have, over the years, complained to the local
Boating and Fishing Officers over what many people consider as excessive quantities of small dead
fish left on the beach by drag netters. Fisheries Officers have made patrols to follow up complaints but
offenders can observe the approach of fisheries officers from a distance and can dump undersized
fish and amend their behaviour prior to the arrival of the officers on the scene.
At the Douglas Shire community meeting of the First East Coast Inshore Finfish Consultation
Process, on 23 October 2006, the issue of unacceptable levels of prawn drag net bycatch being left at
all of the above beaches was brought to the attention of DPI fisheries representatives from Brisbane.
Some people attending recommended that prawn drag netting should be banned.
The writer‟s family initially used a drag net following their move to Wonga Beach in 2000 but ceased
in 2001 following the fatal meshing of around 200 juvenile queenfish in one haul. All these juveniles
died. Since then and up until January 2014, the family has never used a drag net because of this risk.
Following commencing as co-ordinator of the Network for Sustainable Fishing, Douglas Shire, when it
was formed at a community meeting at Wonga Beach in 2007, this writer received a number of
complaints from community members about the amount of drag net bycatch waste left dead on local
beaches.
These complaints prompted articles in two local papers, and articles in two monthly fishing
magazines, the Port Douglas Lineburner (February 2008) and the Mackay published NQ Fish &
Boat (July 2012). No challenges were ever received regarding the material published in these articles
but supportive feedback was.
Following support from the Douglas LMAC, NSF produced a drag net poster (see Appendix 1) to
create awareness of the composition of drag net bycatch and to encourage the use of cast nets rather
than drag nets for bait collection. Lineburner magazine circulated the poster as a flier in a 2011 issue
whilst FFC have it available for download on their website. The poster is also available free from this
writer for anyone requiring multiple copies.
Aim & Methods
The aim of this short study was simply to formally record which species of regulated fish species and
any others of interest that were being commonly caught in beach drag nets over the early part of the
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wet season of 2014 at Wonga Beach. We planned to compare this with the species composition of
those juveniles discarded by prawn netters at Wonga Beach on 10 January 2008 and collected for the
NSF drag net poster.
Since it is illegal to be in possession of undersized regulated fish and they have to be returned
immediately to the water (presumably even if dead) conditions for photographing fish caught when
drag netting are difficult. If the photographer is also dragging the net he is wearing stinger protection
gear, is dripping wet from hauling the net in chest deep water and must work rapidly to “immediately
remove the fish for release” as is required by law.
A total of seven short drags of around 40 metres each were made on 25 January, 1, 2 and 12
February 2014 at three locations between Wonga and the Daintree Estuary. Total time spent dragging
on each day varied from about four minutes on 2 February to about 30 minutes on 25 January. The
net is 14 m x 3 m with 14 mm stretched mesh so is only 2/3rd the depth of the maximum size allowed
and is therefore less effective than the maximum permitted legal size.
The reason for such a short drag period on 2 February was that whilst conditions for dragging were
perfect, an unacceptably high number of juvenile king threadfin were killed during the first and only
haul. We had seen enough and could not justify continuing at such a high casualty rate.
On 12 February we returned to the site we dragged on 2 February because the quality of the close-up
photographs of meshed king threadfins was poor and some had been lost in downloading the files.
However conditions were very different on that day. Three short drags were made with an onshore
wind of over 15 knots. On this day wave height was causing large amounts of flood debris to be
suspended in the water and to build up in the net which was difficult both to drag and to sort through
without taking the entire net out of the water or losing much of the contents. The heavy wave action in
the shallows was probably also encouraging most juvenile fish to remain in deeper water. Catches per
haul were small on that day.
Results
Species selected from discarded bycatch left by prawn draggers on Wonga Beach, 11 January 2008
Those regulated species selected from the bycatch north of Wonga Beach on 11 January, 2008, for
the NSF Drag Net Poster (Appendix 1) and shown here in Plates 1, 3 and 4 include juveniles of
barramundi, grey mackerel, one species of trevally, snub-nosed dart, king threadfin, scaly jewfish and
tongue sole. All of these species are recorded in the literature as occurring in a number of the small
nearby estuaries.
Non-regulated species in the photographs above include sicklefish, silver jewfish, ponyfish, tripodfish,
anchovy and gizzard shad. These were not intended to comprise a comprehensive list of all fish likely
to become prawn bycatch in the area. It is simply a list of fish the writer selected to photograph on that
one day. They were selected from what were clearly prawn bycatch discards left by prawn draggers
on an outgoing tide. There were other species present in the discards that the writer did not record.
A suggestion from SE QLD was widely circulated that a fish kill may have caused the death of the fish
photographed for the NSF drag net poster and that they could not have been caught by beach drag
nets. This statement indicates the lack of awareness of conditions along the beaches of Douglas
Shire. The writer replied to these and other suggestions in detail in a 21 page report dated 13 July
2013. There was however a perceived need for the writer to become directly involved in drag netting
to demonstrate that the findings could easily be replicated during the appropriate season, fish stocks
and annual fluctuations in species population numbers permitting.
Species caught by trial drag netting, Wonga Beach, 25 January – 12 February, 2014
All the regulated species or species groups shown in the NSF poster were caught by the recent drags
described here, with the qualification that two species of juvenile trevally were caught, both different to
the single species collected in 2008. Additional regulated species caught were high numbers of
juvenile giant queenfish (several to many individuals of this species becoming fatally meshed in five
out of the seven drags) undersize swallowtail dart, juvenile and adult whiting and in two drags, many
juvenile snubnose garfish were fatally meshed, and a single juvenile brown sweetlip was released
unharmed. The latter is so well camouflaged amongst the flood debris that many more may have
been missed.
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Most of these species are illustrated either on the Cover or in Plates 1.2, 2.3, 2.4, 2.5, 6.1 - 6.3, 7.1 –
7.10, and 8.1 – 8.3. All the non-regulated species shown in the NSF poster, including sicklefish and
silver jewfish were also caught but little attention was paid to these as the focus was to record the
regulated species, return them to the water and clear the net as quickly as possible.
Discussion
A number of important considerations arise from the observations that every wet season considerable
and unrecorded numbers of juveniles of certain large iconic inshore fish of regulated species perish in
drag nets used on beaches near estuaries in Douglas Shire. Anyone wishing to dispute this should
remain silent until they come to the sites mentioned and try for themselves. It will not take long for
them to be convinced of the truth of the above statement. Meanwhile the Douglas Shire community
and NSF DR have been complaining about falling numbers of large inshore fish species whilst
tripletails (jumping cod), juveniles of which were once common in drag net catches, are now rarely
encountered.
Although mature female fish may each lay millions of eggs annually, mortality during the egg and
larval phases is huge but apparently unmeasured and unknown for local species in the wild. In
unfavourable conditions mortality may even reach 100%. We are advised that climate change, ocean
acidification, pollution from runoff and loss of nursery habitat (and increased levels of dredging and
dumping where this occurs) are already resulting in significant increased levels of stress on our
marine life and may well be further reducing the survival chances of eggs and juvenile fish.
Those life history stages most vulnerable to certain environmental increases in stress levels may be
the egg and larval stages. Individual commercial fish of the „fingerling‟ sizes found in prawn drag net
bycatch may therefore have already survived extremely high mortality rates to reach this stage.
We have little recorded information of the extent or location of nursery areas of species such as king
threadfin and giant queenfish and no attempts have been made to estimate the effect recreational and
commercial drag netting has on their chances of surviving to maturity.
There are no checks and balances in place to limit the impact of drag netting our nursery areas, nor
indeed the amount of gillnetting of their adult populations in spawning aggregations which occur
outside of the barramundi season. If significant numbers of dragnets operate over a significant
proportion of their nursery areas, this may well reduce the numbers of breeding fish.
Since adverse population and environmental pressures are increasing by the year we need to reduce
unnecessary mortality on all stages of the life history of fish to attempt to increase the resilience of our
stocks in every way practical.
In the waters off the Douglas Shire, nursery areas for some inshore philopatric fish estuary species
appear to be limited and, as elsewhere, are under-recorded. We have no means of measuring the
total size and resilience of local resources, or of measuring mortality at different life stages, or of
assessing by how much they have declined from their original abundance.
The commercial fish stocks of the Douglas Shire are also at risk from under-restricted gillnetting, such
that roving or “out-of-town” netters may visit the area at any time and in any number, thus risking
overfishing of small spawning aggregations of iconic species outside barramundi netting closure.
Questions arising:
i) What proportion of nursery areas of our large iconic inshore fish species are swept by drag
nets and what proportion of total numbers of fingerlings in the population perish in drag nets?
ii) How significant is the dragnet mortality of fish that have reached at least fingerling size in
relation to numbers of individuals that recruit to the fishery?
iii) What is the estimated mortality rate of key species prior to fingerling size?
iv) Bycatch exclusion devices used on the offshore prawn trawl grounds in the region apparently
still fail to prevent bycatches of over one tonne of small fish per vessel per night (personal
communication with informed source) and have changed little in volume over the last 20
years, so the question is whether relatively far smaller volumes of drag net bycatch may have
any impact on stocks?
v) Which species are likely to be most vulnerable to this form of growth overfishing?
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Attempted answers
As far as the writer is aware there is no information available to provide answers the questions (i) to
(iii) above.
The answer to (iv) is more straightforward. It is well known that trawl bycatch tonnage can remain high
whilst trawlers, without appropriate bycatch exclusion devices, may in fisheries jargon. „fish down the
ecosystem’. (The writer has not checked for the latest references but does have firsthand experience
of this through working on the Hong Kong inshore pair trawl fishery in the 1990‟s) This occurs where
the most vulnerable species of fish, usually those large top predators with slow maturing rates, are
progressively fished out and the volume replaced by fast maturing, fast reproducing species. The
implication is that just because the volume has not changed this does not mean that the species
composition of the bycatch remains constant or that trawlers are not adversely affecting numbers of
certain species whilst other species flourish.
A contributor to the NSF Facebook recently posted a picture of a threadfin he said was common in
east coast trawl catches and claimed that this was a king threadfin. While it is not possible to be
certain from the photograph (identification to species level in the hand can be confirmed by counting
the number of feelers), the fish appeared to be the puttynose threadfin which is a much smaller, much
faster maturing species commonly recorded in trawl bycatch. It comprised around 1% of the trawl
bycatch in one major NT study.
In response to Qu. (v) above from the limited amount of analysis of bycatch from the recreational
prawn bycatch fishery done so far, the most obvious candidates for growth overfishing by dragnets in
the region are the king threadfin and giant queenfish.
The king threadfin (see Frontispiece) is a species at risk of being overfished in the Douglas Shire (and
apparently already is) because of concerning aspects of both its life history and fishery including:

spawning aggregations may be easily netted in inshore locations

it appears they may spawn both before and after the opening of the barramundi season,
depending on area,

they are strongly philopatric, found mostly or exclusively in inshore waters. A recent analysis
by Captag and Infofish Australia records a 6.5% recovery rate for 2,778 tagged king threadfin
in the Fitzroy River area. For 181 tag recoveries, no fish had travelled more than 70 km,

recent research reveals all or most individuals change sex to become females after eight
years of age at 80 to 110 cm total length, (depending on region),

this is well above the minimum legal size of 60 cm,

there is no maximum legal size to protect the most fecund females as there is for barramundi
which has a similar sex reversal,

the biology of their juvenile stage is poorly known,

at least a proportion of young fish congregate along shorelines regularly fished by drag netters
and readily become fatally meshed in small meshed nets and very die quickly,

commercial gillnetters say that even undersized individuals get their jaws caught in the large
mesh of barramundi nets and die quickly in the net,

there are no checks and balances in place to limit the capture of the species to the production
level potential of local stocks or prevent the extinction of such local stocks,

as a table fish they are comparable to barramundi in regard to the quality.
Threadfin over 80 cm are now rarely caught in waters of the Douglas Shire whilst the literature
records this species reaching 1.7 m in length and 45 kg in weight. It seems a travesty to allow prawn
drag netting in the nursery areas of this truly iconic fish in a World Heritage Area.
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Conclusions
While it would be easy to suggest more study of drag netting bycatch is needed, the observations
presented here and community opinions are confronting. A common sense approach needs to prevail.
A good first step would be to build public awareness that recreational prawn drag netting is a
potentially destructive fishing method if done on a sufficiently large scale in fish nursery grounds.
A pro-active practical local approach would be to identify areas matching the description of likely
nursery area hot spots (beaches near estuaries) and close them to prawn and bait drag netting, whilst
allowing use of cast nets for bait collection but not for prawns for human consumption.
Bait collection elsewhere using cast nets could be promoted as a less wasteful, better option than
drag netting. Even though there may still be some bycatch from cast nets, very few users would ever
cover the nearly same area of ground as is usually covered by prawn draggers.
The NSF drag net poster can help with the required public awareness campaign.
The suggestion has been made there are “bigger fish to fry” than this drag net issue. In response, this
writer suggests that if we wish to continue to have good numbers of bigger fish to fry, we should take
at least some heed of the old saying “take care of the pennies and the pounds will take care of
themselves”. This is even more the case in view of the “pounds” being at risk from all quarters.
The observations and considerations presented here may also be relevant to the use of commercial
bait nets and N11 nets in the Conservation Zones of the GBRMP, about which the author has heard
worrying concerns but has no experience.
Plate 1: Examples of local press coverage
1.1. (above) Cairns Post article, published 1 May, 2011.
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1.2. Port Douglas & Mossman Gazette, 6 February 2012. Note the title is somewhat misleading as barra do
not normally die in drag nets, unlike many smaller juvenile fish.
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Plate 2: Wonga Beach prawn drag netting
2.1 People often illegally pull the net clear of the water to search for prawns in the flood debris,
removing prawns first whilst small fish die amongst the flood debris in the net.
2.2.The bait drag net used by the author in
2014, length 14 m, depth 2 m mesh 14mm.
2.3. Red arrows show fatally meshed juvenile
king threadfin in this section of the net.
2.4. The overlooked problem: fingerlings of regulated
species are fatally meshed in large numbers
2.5. Samples of hundreds (at least) of king
threadfin juveniles fatally meshed at Wonga
beach, 1 – 2 February 2014.
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Plate 3: Examples of prawn drag net bycatch left on the beach, 11 January 2008
(except 3.1 & 3.2, taken earlier)
3.1 Wonga locals with bycatch from a previous occasion
3.3 Juvenile barramundi (Lates calcarifer)
3.2 Wonga local with pile of scaly jewfish he collected
from dragnet bycatch discarded the previous day
3.4 Juv. grey mackerel (Scomberomorus semifasciatus)
3.6 Juvenile trevally, Family: Carangidae
3.5 Juvenile sicklefish (Drepane punctata)
3.8 Juvenile king threadfin (Polydactylus macrochir)
3.7 Juvenile snubnose dart (Trachinotus blochii)
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Plate 4: More prawn drag net bycatch, 11 January 2008 (except 4.3)
4.1 Scaly jewfish (Nibea squamosa)
4.2 Silver croaker (Nibea soldado)
4.4 Ponyfish (Leiognathus sp.)
4.3 Tideline thick with ponyfish from drag netting
4.5 Juvenile tongue sole (Cynoglossus sp).
4.6 Forktail catfish (Family: Ariidae) and tripodfish
(Triacanthus sp.)
4.8 Gizzard shad (Nematalosa come)
4.7 Anchovy (c.f. Thyrissa hamiltoni)
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Plate 5: Crabs found in prawn drag net
bycatch, 11 January 2008, at Wonga
Beach. The crabs are Three-spotted Swimmer
Crab (Portunus sanguinolentus) and Speckled
sand crab (Ashtoret lunaris)
Plate 6: Juvenile barramundi are caught in prawn drag nets, also king threadfin.
6.1. This juvenile barramundi was quickly released apparently unharmed on 2 February 2014
6.2 Close-up of the fish shown above
6.3 This one was being kept in a bucket illegally
by prawn draggers; after discussion with the
author it was released.
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Plate 7: Other species caught in 2014 by the author using a drag net
7.1. Juvenile whiting
7.2. Juvenile of trevally family
7.3. Juvenile silver jewfish
7.3. Juvenile scaly jewfish
7.5. Juvenile brown sweetlip
7.6. Juvenile mackerel, grey, school or Spanish?
7.7. Juvenile threadfin 4 cm, ? king
7.8. Mature poddy mullet, 20 cm, showing roe
7.9 Tripod fish length about 1 cm
7.10. Juvenile snubnose dart
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15
Plate 8. “Gilling” “meshing” and entrapment in prawn drag nets
8.1. These sardines (or pilchards as the case may be) are mostly “gilled” in the conventional fashion
with the mesh jamming under the gill flap. Smaller individuals might push further through and become
jammed with the mesh catching behind the pectoral or pelvic fins, or in the case of the trevally family,
behind the two anal spines peculiar to that family (which includes queenfish).
8.2. This 29 cm whiting must have found a hole in the
net and attempted to force its way through as it had
become firmly enmeshed behind the gills i.e. “gilled”
even though it is far too big to become gilled in
unbroken 14 mm stretched mesh of the drag net.
8.3.These swallowtail dart were simply surrounded by
net and pulled to the edge without any form of
entanglement; they could not find an escape route in
time, similar to the barramundi caught on 2 February.
23 February 2014
16
Appendix 1: The NSF DS recreational drag net poster
23 February 2014
17

Recreational prawn drag netting in Far North Queensland

Transcription

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