By-Catch Reduction/ Trawling

[blaze]

If thats the case Derek, maybe the pro's are fudging there figures to show increase catch. I believe in Tassie there is going to be some changes in the pro squid catch quota, I know a pro who is recording squid as catch even though he doesnt catch many and logging it as bait so he has "PAST HISTORY" if the changes happen.
The data can be written to an extent to show what they want
cheers
blaze
ps
great effort Kev

[bidkev]

[quote author=Reel Nauti link=1143797596/45#58 date=1144482635]The catches seem to have increased right across the board Kev.

Both the total trawl stats and the otter trawl stats clearly show a reduced number of boats working, a reduced amount of nights fished, yet very significant increases in harvest tonnage. How can this be??

It's got me buggered.

Cheers and good work Kev

Dave

Dave

Maybe, just maybe those stats are saying that there IS a sustainable pro fishing industry out there.


Derek
[/quote]

That may well be Derek but it needs more looking into. Is it the prawn catch that's bumped the figures or the "incidentals" such as squid, pinkies etc? I know that I see a lot more pinkies around nowadays than I used to, although a lot less squid. Also, the beam trawl fishery can be pretty mobile. Are they simply fishing previously unfished areas (well stocked) waters or simply working more effectively? Or, as you say, the fishery is proving sustainable due to the measures in place?

Lacking a full breakdown of the catch, if we assume that the catch consists in the main of the target species (prawn) then that's a lot more prawn taken out of the food chain than previously.

kev


You are absolutely unique. Just like everyone else.

[Derek_Bullock]

[quote author=Derek Bullock link=1143797596/45#59 date=1144484555][quote author=Reel Nauti link=1143797596/45#58 date=1144482635]The catches seem to have increased right across the board Kev.

Both the total trawl stats and the otter trawl stats clearly show a reduced number of boats working, a reduced amount of nights fished, yet very significant increases in harvest tonnage. How can this be?? #

It's got me buggered.

Cheers and good work Kev

Dave

Dave

Maybe, just maybe those stats are saying that there IS a sustainable pro fishing industry out there.


Derek
[/quote]

That may well be Derek but it needs more looking into. Is it the prawn catch that's bumped the figures or the "incidentals" such as squid, pinkies etc? I know that I see a lot more pinkies around nowadays than I used to, although a lot less squid. Also, the beam trawl fishery can be pretty mobile. Are they simply fishing previously unfished areas (well stocked) waters or simply working more effectively? Or, as you say, the fishery is proving sustainable due to the measures in place?

Lacking a full breakdown of the catch, if we assume that the catch consists in the main of the target species (prawn) then that's #a lot more prawn taken out of the food chain than previously.

kev


You are absolutely unique. Just like everyone else.
[/quote]

I hope it is right Kev but from my years of experience working in Government I am very much aware as to how statistics can be used for whatever purpose you want.


Derek

[bidkev]

[quote author=kingtin link=1143797596/60#61 date=1144489849][quote author=Derek Bullock link=1143797596/45#59 date=1144484555][quote author=Reel Nauti link=1143797596/45#58 date=1144482635]The catches seem to have increased right across the board Kev.

Both the total trawl stats and the otter trawl stats clearly show a reduced number of boats working, a reduced amount of nights fished, yet very significant increases in harvest tonnage. How can this be??

It's got me buggered.

Cheers and good work Kev

Dave

Dave

Maybe, just maybe those stats are saying that there IS a sustainable pro fishing industry out there.


Derek
[/quote]

That may well be Derek but it needs more looking into. Is it the prawn catch that's bumped the figures or the "incidentals" such as squid, pinkies etc? I know that I see a lot more pinkies around nowadays than I used to, although a lot less squid. Also, the beam trawl fishery can be pretty mobile. Are they simply fishing previously unfished areas (well stocked) waters or simply working more effectively? Or, as you say, the fishery is proving sustainable due to the measures in place?

Lacking a full breakdown of the catch, if we assume that the catch consists in the main of the target species (prawn) then that's a lot more prawn taken out of the food chain than previously.

kev


You are absolutely unique. Just like everyone else.
[/quote]

I hope it is right Kev but from my years of experience working in Government I am very much aware as to how statistics can be used for whatever purpose you want.


Derek
[/quote]

Well Dave and Derek, now we digress

On the one hand, you've got the pro fishers who know that they've got to show a sustainable fishery or they get chopped, on the other hand, you've got a bunch of pollies who know that they've got to show sound economic sense. Chop the fishery too much, and there's less going into the economy, don't chop it, and you get every pressure group from greenies to rec fishers jumping down your throat.

Howzabout, we (the pollies) just *look* like we're chopping it, and let the pro fishers look after it themselves? *They* can log the catches and we'll trust to *their* sound economic sense to ptotect themselves. While we're at it, let's import some of that cheap Viet seafood and let the pros export their more valuable catch.........that'll help the balance of trade deficit. Makes sound political sense?

Now where was it in this thread that cynicism was mentioned?

Seriously, I've found nothing yet to convince me that all catches are adequately policed (verifiable).

kev

An election year is the time politicians want to help us out of all the trouble they got us into in the first place.

[bidkev]

Partitioning of material discarded from Prawn Trawlers in Morton Bay

TJ Wassenberg and BJ Hill

Abstract

Prawn trawlers in Moreton Bay, Queensland, discard about 3000 t of material each year. About 3% floats, and the rest sinks. The floating component is almost entirely fish. At night, floating discards are eaten by silver gulls (Larus novaehollandiae), crested terns (Sterna bergii) and, to a lesser extent, dolphins (Tursiops truncatus). There is little trawling during the day but the last discards are dumped overboard around dawn. At this time cormorants (Phalacrocorax varius) join the scavengers. Birds and dolphins scavenged only fish and cephalopods, and not crustaceans nor echinoderms. Birds are selective as to the size of fish they will eat, but most of the whole fish in the discards are below 50 g, and the largest fish that crested terns ate was 100 g. Dolphins are capable of taking the largest of the discarded fish.

Most of the material that sinks is crustaceans (54%) and echinoderms (18%); the rest is elasmo- branchs and rubble. At night, about half of the fish that sink are eaten by diving birds and by dolphins. There was no indication of mid-water scavenging of sinking discards, except for cormorants and dolphins in the upper water column. Approximately 11% of the discards that reach the bottom comprise fish and crustaceans, which are eaten by crabs (Portunus pelagicus) and fish. The remainder- chiefly crabs, echinoderms and elasmobranchs-reach the bottom alive. Altogether, about 20% of discards are eaten by surface and bottom scavengers.

That's 6000tons of by-catch estimated scavenged in Moreton bay alone

[bidkev]

This may be dated but may be of interest to guage socio-economic impact of closure

CRC Reef Research. 2000 Social Profiles of Qld's Fishers

Groups of towns and communities that depend on each other are called Town Resource Clusters (TRCs). Based on the homeports used by fishing businesses, 22 TRCs were described along the Queensland coast. Many TRCs included a major regional centre (where most fishing businesses were based) and smaller nearby communities. The researchers used Town Resource Cluster Analysis (TRC-analysis) to look at the links between the fisheries and the communities that depend on them. For each fishery, information about fishing location that was given during the interviews was plotted on a 15-minute grid so that areas of high, moderate and low use for each homeport could be identified.

Most Queensland fishing businesses were based in Queensland, with 2% based in New South Wales. Brisbane TRC had the highest number of fishing businesses (17% of the total), closely followed by Bundaberg (13%), Mooloolaba (9%), Cairns (8%) and Townsville (7%) TRCs. Many fishing businesses (44%) were based adjacent to the boundaries of the Great Barrier Reef Marine Park – between Cooktown and Gladstone.

FISHING ACTIVITY
Most fishers said that they went trawling (47%) and line fishing (42%) with fewer fishers saying they were involved in netting (31%) and crabbing (24%). Brisbane (18%), Bundaberg (13%), Cairns (12%), Mooloolaba (10%) and Townsville (9%) TRCs were the homeports where most trawl fishers lived. These TRCs together accounted for 62% of the trawl fishing businesses in
Queensland. Most fishers who went line fishing were based in homeports in Bundaberg (15%) and Mooloolaba (11%) TRCs, while those who went crabbing were most often based in Bundaberg (13%) and Brisbane (23%) TRCs. Net fishers were most commonly from Brisbane TRC (21%), but were also often based in Bundaberg (9%) and Innisfail (7%) TRCs. Most fishers said they engaged in more than one fishery. For example, in the 12-month period, 32% of line fishers also engaged in netting, 28% in crabbing and 24% in trawling. Likewise, 67% of those conducting crabbing also engaged in netting and 46% of those fishing for spanner crabs also engaged in line fishing.

LOCATION OF FISHING
Fis
In general, most fishing activity was reported to take place to the north of the homeport. Areas of high and moderate use were mapped on a 15-minute grid for each fishery. Fishers said that the most common areas for trawl fishing were in Moreton Bay, Princess Charlotte Bay, coastal areas between Port Douglas and Cairns, Innisfail and Bowen, and between Yeppoon and Hervey Bay.
Line fishing was reported to be concentrated on the Swain Reefs and reefs to the east of Mackay, coastal areas between Moreton Bay and Yeppoon, and numerous coastal areas between Airlie Beach and Port Douglas.

Net fishing often occurred with other fishing activities in Queensland. The most common areas reported for net fishing activity were Moreton Bay, areas surrounding Fraser Island, Hervey Bay and Tin Can Bay, and coastal areas between Yeppoon and Gladstone. Fishers reported crabbing in similar places to net fishing: in Moreton Bay; areas surrounding Fraser Island and; coastal areas between Yeppoon and Gladstone.

SIZE OF BUSINESS
Fishers said that most fishing businesses in Queensland (64%) operated one fishing boat during the 12-month period. The average number of boats was highest for operations in Maryborough (3.0), Ayr (2.6) and Weipa (2.0). Most of the boats (61%) operated by businesses were 3–10 metres long. Only 6% of boats were over 19 metres. Smaller boats were operated from Lucinda, Ayr, Airlie Beach and Maryborough TRCs, with larger boats operating from Cairns, Townsville, Gladstone, Harvey Bay, Tin Can Bay and Southport TRCs.

BUSINESS INCOME

Gross Value of Production (GVP) is the price received by the fisher for the product at landing. Based on figures for the 12 months prior to the survey, it was estimated that the 2,444 commercial fishing businesses in Queensland had a GVP of approximately $314 million. Cairns ($53 million),
Bundaberg ($37 million), Townsville ($35 million) and Brisbane ($33 million) TRCs together accounted for about half of the commercial fishing GVP for Queensland that year.

EMPLOYMENT
Most businesses said they had 2–3 full-time employees (including the owner or operator). In total, it was estimated that there were 6,110–7,088 full-time equivalent employees. There was little part-time or casual employment by these businesses. I would think this is suspect.

BUSINESS OWNERSHIP

The average number of years all fishing businesses in Queensland had been operating was 18.2 years. Nearly half of all businesses had operated for less than 10 years, and about one-third of all businesses had operated for less than 5 years. Fishing businesses in Queensland had been owned by the same operator for an average of 14.6 years. The average length of ownership by a current
business was longest in Southport (21 years), Thursday Island (20 years), and Airlie Beach, Maryborough and Yeppoon (18 years). About half of the fishing businesses had been owned for less than 10 years, with 28% being owned for less than 5 years.

OWNER/ OPERATOR AND EMPLOYEE INCOME

Queensland fishing business owners/ operators said they earned an average annual income of $39,420, and employees an average income of $20,653. In some cases, these figures are based on the responses to the survey of as few as 5 fishers. See profiles for each TRC to check the
sample size. The average income of owners/ operators in Cairns, Tin Can Bay, Hervey Bay and Ayr TRCs were reported to be much higher than the Queensland average. In contrast, the income of owners/ operators in Cooktown, Weipa and Port Douglas TRCs was much lower than the Queensland average. The highest earning employees were in Karumba, Tin Can Bay, Thursday Island, Cairns, Airlie Beach and Hervey Bay TRCs, with salaries much higher than the
Queensland average. The lowest average employee incomes were recorded in Yeppoon, Bowen, Brisbane and Mackay TRCs. These figures do not take into account seasonality of different fishing activities

[bidkev]

where waldo... mm back again.... it seems odd top me that an industry that [recco fishing] that operates in an unregulated and unlicensed manner vieing for the use of the same resources as we pay for should have the gall to drag up facts and figures on bycatch to try and prove ur point. what it proves to me is that we are very aware of these issues and have been working for 15 yrs now to address these issues. recently i trialled a new type of bycatch redustion device which showed an initial result of 66% exclusion of bycatch . to point fingewrs and say this should be legilslated or that shud be legislated is a moot point it already has. im not getting on this site dragging out research on how much harvest is being done by ur industry in an uncontrolled/unregulated/unlicensed manner. until the recco industry can quantify what ur actual harvest per yr is empirically thru log books [ not phone survey estimates] until the recreational industry can account for effort creep thru gps,plotters sounders and all the electronic equipment that allows u to target specific areas [ in ur 10s of thousands] until u guys can account for the effort creep resulting from 50 thou people a yr moving to s e qld for the 'seachange' i dont think u guys have a leg to stand on. we know what our problems are and with cooperation from gov we are working to minimise our impact. ur industry is a chicken little bloating andrunning out of control every yr placing more and more pressure on the same resource. sumone made the comment bout pointing fingers and dirty hands well back at u.

Hi Waldo,

Mate, see the thread on general page entitled By-catch/ trawling. I'm attempting to "not point the finger" but illustrate what is being done, and ascertain as to whether more should be done, to protect the fishery. There was considerable concern voiced on this site and in the media regarding the kill on the Sunny. Also the trawling effort in the Pine and Logan is of great concern to reccos and the general public alike.

There is considerable anecdotal evidence regarding many dead herring, mullet and whiting in the Pine and also issues regarding the disturbal of the bed when trawling is underway. We all know that herring, once handled, are as good as dead, these being a considerable constituent of the food chain. Concern was also voiced as to the number of licences operating in such a small fishing area as the Pine.

I am re-assured through this research, that Fisheries are doing as much possible at this time (via budgetary constraints) to eliminate by-catch and arrive at a consensus on what is "sustainable fishing practice".

I am also aware of your concerns regarding logging of rec fisher's catches and the legislation regarding pros logging. In reality, neither is of much use unless it is verifiable and proven to be honest, and my current research leads me to believe that neither are a reliable indicator of the state of the fishery.

This from the WWF dated 2003. I am not aware that anything has changed since then, but would welcome any current info:

"The QFS report acknowledges that there are currently no processes in place to validate catch
and effort information provided through the logbook program; therefore, the degree of
reliability of commercial catch and effort data through the logbook program is unknown.

Individual species need to be dealt with separately when developing estimates of removals
from commercial, recreational and indigenous fishing, and when undertaking stock
assessments and identifying species catch levels. It is unfortunate therefore that the report
tends to lump together groups of species. For example, references are made to tiger prawns
when in fact there are three species of tiger prawns caught and landed by the ECOTF: the
brown tiger (Penaeus esculentus), the grooved tiger (Penaeus semisulcatus) and the relatively
rare giant tiger (or leader) prawn (Penaeus monodon). Further, references are made to
endeavour prawns when there are two species of endeavour prawns landed by the fishery: the
true or blue endeavour (Metapenaeus endeavouri) and the false or red endeavour"
(Metapenaeus ensis)

And this from the same source which I am quite happy to publish if even to show that I am not operating from a one-sided viewpoint:

"In addition, the lack of a recreational fishing licensing regime in Queensland seriously
hampers the capacity of the QFS to monitor recreational fishing catch and effort."

I haven't really got time to handle two thread on this Waldo, so I am going to move this response over to the By-Catch/trawling thread. Your input is valued and you may have a better chance at putting your point across over there. Hope this sits well with you

kev

[fisher28]

[DaveSue_Fishos_Two]

Waldo

I'm not trying to stir the pot here but we rec fisho's are quite well controlled with bag limits, size limits etc.

I don't feel that we are trying to 'compete' with you. Most of us have much respect for you pros and what you are doing to put food on your table and feed the masses. We can surely learn from one another and surely we can 'share'.

Certainly you guys pay a hell of a lot of money to do what you do, fuel, maintenance, licence fees and the like. You blokes are making a living from the sea, the recs are not. There is no competition, but there has to be tolerance, understanding, and respect from both sides. Surely??

Cheers
Dave

[rando]

Waldo
I made the comment about not pointing the finger and I made it in relation to the fact that you are continually shifting blame for loss of fish stock.
In your eyes its developement or pollution or loss of habitat or anyone elses fault but not yours , you are quite happy to consider any cause except you own activity.
When from my perspective the single most damaging thing that happens is trawling, and it is far and away more damaging than all the other causes combined.
rando

[CHRIS_aka_GWH]

#recently i trialled a new type of bycatch reduction device which showed an initial result of 66% exclusion of bycatch

waldo,

I am genuinely interested in how the figure is derived ?
Do you compare previous bycatch figures to post fitting of the excluder bycatch figures?



66% exclusion ....

for every one I take by accident two are excluded.
I take a third of what I don't want, but pass thru .... by accident.

This figure incidently doesn't reflect bycatch as a proportion of catch.

chris

[bidkev]

Square Mesh Panels

One of the most successful modifications has been square-mesh panels in codends. Put simply, square-mesh panels in codends work by exploiting the behavioural differences between prawns and fish.

Fish, unlike prawns, show 'herding' behaviour when they detect a trawl net approaching. The fish try to keep a position with the moving net until they tire and fall back towards the codend. As the fish are herded together, the balance of the school is upset, and the fish try to escape by heading towards the top and sides of the codend. In the process the fish often escape through the open square-shaped meshes.

By contrast, prawns have a limited reaction to the trawl. The flow of water generated by the trawl quickly forces them against the meshes, and they eventually tumble along the bottom of the net into the codend.

The size of square-mesh used in the panel directly determines the size of fish that are allowed to escape. Preliminary studies in the oceanic prawn trawl fishery have shown that codends with relatively small panels of square-mesh were effective in removing up to 40% of the total unwanted bycatch. For some species, the reduction of juveniles was 70%.

Square-mesh panels have been used in estuaries to exclude species such as mulloway and catfish. In the Hawkesbury River, square-mesh panels were effective in reducing the numbers of these fish by up to 40% and 50% respectively.

[bidkev]

From research done in an overseas fishery but just as likely to be an indicator in our fisheries.

The Fate of Escapees

Due to pressure on fisheries to reduce bycatch and discarding, trawl fishers have responded
by utilizing a mixture of bycatch reduction devices, such as bird’s eye escape holes, Nordmore grates, escape panels, and larger or square mesh codends.

These devices have been moderatelysuccessful in some fisheries at reducing the number of unwanted and under-sized fish that reach the deck. How-ever, as the observed bycatch and rate of discard decline, the question remains: Do fish escaping trawls via bycatch reduction devices actually survive?

Studies in Europe have utilized cages that surround the codend and retain escaping fish, thereby allowing monitoring of their survival over time. These studies have indicated that survival can be highly variable among species, with direct mortalities of 10% -30% being common for escaping fish. For fragile species such as herring, mortality can be as high as 70%. Arguably, these fish should be considered part of an unobserved bycatch. Studies of walleye pollock, conducted in conjunction with the RACE Division, indicate that mortality of walleye pollock escaping through a 93-mm square mesh overhead escape panel ranged from 40% to 80%, depending on whether fish exited the net in the codend or in the intermediate (the section of net in front of the codend).

As in the European studies, fish escaping the trawl were retained in a cage which was detached and moored after the tow, then monitored for mortality over 14 days. An unintentional consequence of this methodology is that the caged fish are protected from the natural rigors of life in the sea, most notably predation. As such, these numbers likely underestimate true unobserved bycatch, as they do not include fish which become behaviorally impaired and succumb to predation in hours or days after escape. Because field studies of the effect of trawl-passage upon vulnerability to predation are logistically impossible, we addressed this issue in a series of laboratory experiments.

Age-0 walleye pollock (17.1 -21.6 cm total length) were sequentially subjected to stressors simulating those experienced during trawl passage; sustained swimming, crowding, and escape through codend meshes. The fish escaped into a tank containing a larger sablefish(48-53cm),where the pollock anti-predator behavior could be quantified. Having undergone simulated trawl passage, the pollock exhibited significant impairment in anti-predator behavior compared to control fish; they swam slower, shoaled less cohesively, and allowed the predator to get closer. Importantly, behavioral impairment was correlated to the magnitude of the stress, as fish exposed to swimming, followed by escape, were less impaired than fish that also experience crowding. Behavioral impairment lasted at least 2 hours, with fish recovering within 24 hours. In subsequent experiments, when trawl-stressed walleye pollock, along with control fish, were exposed to predation by a lingcod (48 -60 cm), the trawl-stressed fish were consumed in greater numbers.

We have conducted these identical experiments with juvenile sablefish. From prior experiments
we know that sablefish are more “durable”(i.e.,morerobust), being able to survive physical stressors that typically kill walleye pollock. Nonetheless, sablefish still showed the identical behavioral impairments resulting from sublethal stressors simulating entrainment and subsequent trawl escape. This suggests that behavioral impairment from stress may be a ubiquitous effect, influencing the survival of both durable and fragile fish species. Perhaps more importantly, this work suggests that the fact that bycatch does not appear on deck, does not mean that those fish have been released from the gear unimpaired and are capable of surviving. While a laboratory study cannot predict the numberof fish consumed by predators after escaping trawls, it does suggest that reducing the time non-target fish spend in the gear and hence the cumulative stress they incur, will minimize both direct and predation-mediated mortality.

Delayed Mortality

Delayed mortality of discards may be common and can occur over an extended period of time after capture and release. This can result from 1) physical injury and wounding associated
with capture, 2) physiological injury associated with environmental factors, and 3) indirect mortality resulting from predation and disease. Delayed mortality is difficult to measure in the field because of the logistical problems of holding fish for long periods of time in cages, net pens, or tanks. Tag and re-capture studies measure delayed mortality, but give no information about the time course of mortality. To investigate the principle of delayed mortality associated with bycatch, we held fishes in the laboratory under controlled conditions for up to 60 days after exposure to bycatch stressors and found delayed mortality (100%) in Pacific halibut and sablefish after 30 days, walleye pollock after 14 days, and lingcod after 1 day. Delayed discard mortality indicates the presence of sublethal effects of bycatch stressors that may eventually result in indirect mortality from predation, physiological stress, or disease. We also observed behavioral deficits in orientation, startle responses, swimming ability, phototaxis, feeding, schooling, social interactions, and predator evasion in walleye pollock,sablefish, Pacific halibut, and lingcod exposed to bycatch stressors. These behavioral deficits ultimately resulted in increased mortality caused by fish predators in our laboratory. Although laboratory experiments are not necessarily comparable to field conditions, it is intuitively obvious that capture-impaired fish have a reduced ability to avoid predation.

Summary

Past efforts at understanding and reducing bycatch mortality have focused on modifying fishing gear to avoid capture of potential bycatch and to reduce physical injury to fish that are caught in fishing gear. Fish experience stress from physiological injury and behavioral deficits that may not be readily apparent to human observers, but may result in significant direct or indirect mortality in discards and escapees. Bycatch mortality is linked to environmental (light conditions, temperature, air exposure) and biological (behavior, fish size and species) factors and their interactions which have not been previously investigated in any detail. Research in a laboratory setting under controlled conditions allows for a systematic investigation of bycatch stressors and furthers our understanding of key principles of bycatch mortality.

This article is based on “Key principles for understanding fish bycatch discard mortality”
by Michael W. Davis, which appeared in the November 2002 issue of Canadian Journal
of Fisheries and Aquatic Sciences.

[rando]

Great read Kev
Thanks again for your efforts in informing us and your balanced approach.
.
You are a very diligent researcher and I look forward to your next installment .
rando

[bidkev]

Department of Agriculture, Fisheries, Forestry - Australia

Non-target species

Fishing not only harvests species that are sought by fishers, but also significantly affects species that are not sought or wanted. We use the term non-target species for those species (including fish, sharks, crustaceans, mollusks, marine mammals and reptiles) that are unintentionally taken by the fishery or are not routinely assessed for fisheries management. The term usually relates to an entire fishery and its management and not to the targeted fishing activities of individual fishers.

Commonwealth fisheries management requires that fisheries resources are exploited with regard for the effect of fishing on non-target species. What needs to be done in order to satisfy this requirement is becoming clearer but there is little empirical evidence or applicable theory to address the relevant questions.

The 1999 BRS report Non-Target Species in Australia’s Commonwealth Fisheries examines the information available on non-target species in Commonwealth fisheries—the amount and composition of the catch, the fishery-specific issues, previous assessments of fishing effects, and assessments required in the future.


Current understanding of the effects of fishing on ‘non-target’ species in Commonwealth fisheries comes from several sources of information: onboard monitoring of commercial vessels by scientists and observers; systematic fishery surveys; commercial and exploratory surveys; catch logbooks and dockets filled out by fishers; information from adjacent fisheries; and anecdotal reports. Logbooks are often an incomplete source of information since they mainly record the retained catch and do not adequately record the non-target species which are often discarded. The most comprehensive and reliable sources have been onboard monitoring and scientific fishery surveys explicitly aimed to record non-target species.


Though it is possible to obtain a qualitative indication of the composition of the catch, there is insufficient quantitative information to be confident of the actual amount and composition of the non-target catch in most fisheries. Exceptions are the main prawn (Northern Prawn Fishery, Torres Strait Fishery) and fish trawl (South East Fishery) fisheries, and the longline tuna fisheries ( Eastern Tuna and Billfish and Southern Bluefin Tuna). Overall, the available information on non-target catch and composition could best be described as snapshots of some fisheries.

Much of the non-target catch is discarded, particularly in trawl fisheries. The proportion discarded is largest in the major prawn and fish trawl fisheries. Fisheries such as the squid jig and purse seine fisheries are highly selective and have little non-target catch and almost no discards. Even within a trawl fishery, however, the level of discarding can vary greatly by region, season and fishing operation. In the tropical prawn fisheries, discards are rapidly eaten by birds, dolphins, sharks and bottom scavenger fishes. We do not know the fate of the discards in other fisheries and it will be different to that observed in tropical prawn fisheries.


In most Commonwealth fisheries there are non-target species caught that are considered vulnerable to fishing or have a favoured status with the public. Species of most concern are albatrosses in southern waters particularly in the Southern Bluefin Tuna and Macquarie Island fisheries and turtles in northern tropical waters particularly in the Northern Prawn and Torres Strait fisheries. There are several other species such as sharks, sawfishes, seabirds, snakes and seahorses that have been nominated as vulnerable or endangered in various national or international forums. Marine mammals tend to have a favoured status. Dolphins and whales are not a catch of any Commonwealth fishery except in the rarest of circumstances. Seals, however, are caught in several southern Commonwealth fisheries.

Generally, there is rarely sufficient information on the catch of species of public concern to quantify the fishery mortality and determine the impact of fishing on their populations. For example, though there are some records of seal catches, the fishing mortality and the effect of discards cannot yet be assessed to reliably determine which fisheries have a detrimental, beneficial or insignificant effect on the seal population. In the main, vulnerable or favoured species have been identified in response to national or international concerns as to the status of their populations. There is now positive action being taken in Commonwealth fisheries to assess the vulnerability of the non-target species taken in their catch, and research projects and observer programs have been put in place to assess and quantify the effect of fishing on species of public concern.

Interactions arise between fisheries when the non-target species of a fishery is the target species of another fishery. They complicate the assessment and management of a fishery and can lead to tension between fishers. Factual information on the catch and an accurate assessment of impact can define the problem, identify solutions and significantly reduce this tension.

Significant fishery interactions occur in about half of the Commonwealth fisheries. They are more pronounced in the more populous Southern and Eastern part of Australia where several Commonwealth fisheries occupy common areas or are adjacent to important State fisheries.


The question is increasingly being asked if a large catch of only one species has a more pronounced ecological effect on a marine animal community than a similar catch spread across many species.

To date, concerns over the ecological effects of fishing have been raised mainly in the larger Commonwealth fisheries using trawl gear such as the Northern Prawn Fishery and the South East Trawl Fishery. However it would be unwise not to consider the possibility of ecological effects in fisheries removing large amounts of prey species such as jack mackerels or moderate amounts of high-level predator species such as tuna.

Discards of large amounts of dead ‘non-target’ catch redistribute food to different trophic levels and can have ecological implications that are not well understood. These may be considered positively or negatively depending on the values we place on different animals. There is a need however for caution even though these discards may seem to benefit populations of desirable species. Subsequent reductions in discards may leave the population more vulnerable than it had previously been if the effect of this increased food source was to also increase populations of competitors and predators.

There are few comprehensive assessments of the effects of fishing in Commonwealth fisheries.