By-Catch Reduction/ Trawling

[bidkev]

The Environment Likely to be affected by the Fishery

There are approximately 267km2 of seagrass in inshore and estuarine waters of southern Queensland (Hyland, Courtney & Butler 1989) and about 5000km2 of seagrass between Cape York and Hervey Bay (Lee Long & Coles 1997). There is currently limited data on Queensland’s river and estuary environment, however, the Department of Primary Industries and Fisheries’ Marine Habitat unit is conducting an ongoing program of studying and documenting fisheries resources in Queensland’s river systems providing baseline data from which informed management decisions
can be made.

Fishing and associated practices that disturb the substrate such as beam trawling may remove benthic habitat and cause changes to the abundance of some species (Zeller 1998). Beam trawling has been shown to remove dead timber and other snags from estuaries (Dredge 1983). Snags support higher fish diversity and are important to a range of estuarine fish of economic importance (e.g. flathead, bream, and moses perch) (Zeller 1998). Snags in estuaries provide habitat values similar to reefs, acting as refugia from predators and cover to ambush prey (Sheaves 1996
cited in Zeller 1998, Robins & Courtney 1998).

However, several studies (Hyland 1988, Coles and Greenwood 1986, Dredge 1983, Gibbs et al 1980) found that the environmental disturbance caused by beam trawling is minor compared to other natural and human induced impacts (e.g. floods, tidal action, dredging, urban and agricultural runoff) (Milward, Morton, Tilbury 1994).

Previous studies by DPI&F (Dredge 1983, Hyland 1988) found beam trawling to have little impact on finfish stocks. Incidental catches of commercially or recreationally valuable finfish comprise less than 10% of beam trawl catches. With the possible exclusion of river perch stocks in Moreton Bay, there is no evidence that beam trawling has affected stocks of species important to other fisheries (Dredge 1983,Hyland 1988)

Comment from me:
Note here that the last para research was done in 1988. I haven't been able to find any later studies. I would also argue that even if the figure is only 10%, data sources back then were totally unreliable by todays standards and I don't think that 10% of the total catch is insignificant

They are also missing the point that degredation of a fishery doesn't simply rely on decimation of stocks due to by-catch. The actual targetted species are invariably part of the food chain that would deprive finfish of some, if not most, their staple diet. How many times has it been stated on this site that prawn is the favoured bait in areas such as the Pine, Logan and Broadwater/Pin? remove the prawns and the fish move on or at the least lose the condition that affects breeding.

kev

[bidkev]

‘Bycatch’ as defined in the Guidelines are:
*discards of commercially valuable species;
*species that are discarded from the catch;
*fish that are retained for scientific purposes;
*that part of the catch that is not landed but is killed as a result of interaction with fishing gear.

Non-target, commercially valuable species taken and retained as by-product arerequired to be recorded in logbooks under the Trawl Plan. Other non-target bycatch species (excluding sea turtles and other megafauna) are usually brought on board, sorted from the targeted product and discarded without being recorded.

Logbook amendments introduced in 2002 include the requirement to report all species that are of conservation concern listed under the EPBC Act 1999 that are taken as bycatch. There is no requirement however to report discarded bycatch species unless the species is of conservation concern listed under the EPBC Act 1999.

There are limited data available on bycatch taken in the River and Inshore (beam) Trawl Fishery (RITF). Hyland (1985, 1988) documented commercial prawn catch details from four estuaries that run into Moreton Bay (T5 area) and undertook a detailed (monthly, weekly peak fishing season) experimental sampling program of beam trawl bycatch in and adjacent to the Logan River estuary. Hylandalso documented bycatch from the commercial fishery in three of the four estuaries through an intermittent sampling program and gave an estimate for total take of certain bycatch species. Hyland states “ The rivers in the Moreton Bay region have been exploited by beam trawlers continuously since the 1940’s. There has, during the same period been similarly continual fisheries for bream, perch and whiting. Simultaneously there has been an increase in recreational effort, increased alternative uses of the aquatic resources and a reduction in available nursery areas
through coastal development. To highlight the effects of beam trawling on the river substrate as being the cause of reported reduced angler success ignores all of the likely contributing effects” (Milward, Morton & Tilbury 1994).

A Synopsis of RITF Bycatch Research Findings
Hyland (1985: T5 Fishery Area);
*93 species from 51 families were sampled, with more than 50% of the wet weight discarded by commercial fisherman;
*eight species accounted for 92% of the total catch by abundance and 12 species made up 90% by weight;
*the direct mortality on these species is unknown, though Acanthopagrus australis (yellowfin bream) is caught in considerable quantities but appears to survive trawling and catch statistics do not indicate a decline of the species;
*johnieops vogleri (river perch) is of most concern as it was caught in relatively large numbers and does not appear to survive trawling.

Hyland (1988: T5 Fishery Area)
*the most abundant fish species in the standardised samples was the blue catfish, Arius australis.
*three of the more abundant species are important recreational or commercial species: yellowfin bream (Acanthopagrus australis), river perch (Johnieops vogleri) and the winter whiting (Sillago maculata).
*any declines in finfish or any other environmental damage cannot be attributed to beam trawling without considering all other impacts such as pollution and urban and agricultural runoff.

Dredge (1983: T7 Fishery Area)
*108 species identified with only 9 being of significance to recreational or commercial fisheries.
*the only fish species of economic value taken in sufficient numbers to warrant concern were mud flathead (Platycephalus fuscus), the grunters (Pomadasys spp.) and bream (Acanthopagrus australis).
*only bream were caught at all sites throughout the entire year of sampling.
*juvenile bream and flathead were found to be vulnerable to trawl mortality.
*beam trawling, with the exception of removal of snags.results in negligible disturbance compared with disturbances caused by construction, siltation and pollution.

Reid and Campbell (1998: T5 Fishery Area)
*found no evidence to suggest that beam trawling had a severe and continuing effect on finfish stocks as there is no noticeable consistent decline in recreational catch rates over the last 75years.
*bycatch survey results consistent with previous studies.
*significant species caught were yellowfin bream, winter whiting, flathead andriver perch.

I find this last one to sound far from credulous. How were they recording rec fishers' catches 75 yrs ago and how reliable was it? No decline in recreational catch rates? does this take into account the increased population of today? If not, then this statement is seriously flawed. I shall have to try and find Reid and Campbell's research and see how they arrived at this conclusion. I think it is clear to all rec fishers that we don't catch fish like grandpa did, despite the the technological aids at our fingertips.

[bidkev]

A risk assessment approach developed for the NPF (Stobutzki et al 2001) can be applied to the QECTF. This approach offers a useful method of classifying bycatch information. The first step in managing bycatch is to identify bycatch species and determine any temporal and spatial variations in distribution. Based on the IUCN system of classification for endangered species, Stobutzki et al, developed a matrixfor the classification of bycatch in the NPF.

Approximately 400 species were examined in relation to their “susceptibility to capture” and their “ability to recover” from the effects of trawling. A species’ susceptibility was determined using factors including position in the water column, preferred habitat, survival, range, day/night
catchability, diet and depth range. Capacity to recover was determined using factors including probability of breeding, maximum size, removal rate, reproductive strategy, hermaphroditism and mortality index. An overall score was given to each species according to these two main sets of criteria and the outcome was presented in the form of a two dimensional graph (Huber 2003).

This classification is a useful first stage in identifying species that are most at risk, however it contains several limitations. Other studies are being developed to address these limitations building on Stobutzki’s work (Huber 2003). DPI&F is actively liaising

Ecological Assessment of the River and Inshore (Beam) Trawl Fishery with Project Teams developing Ecological Risk Assessment processes for use in the QECTF. The process of risk assessment is being developed quickly – the current CSIRO model splits impacted species into three categories (low, medium, high risk) in the basis of biological characteristics (longevity, distribution, fecundity etc). It then effectively dismisses the low risk species, and undertakes a semi-quantitativeanalysis to the medium risk species. High risk species should be the subject of more detailed analysis. Applying such an analysis to the 200 plus species taken as bycatch in the RITF given the scale of the fishery and lack of any evidence of significant impacts is not a high priority for the DPI&F

By it's own admission there has been little research into the beam trawl industry with regards to by-catch mortality on escape/discard. I would have thought that in light of this, there would be even more pressing need for research, and not as it implies here, to low prioritise it simply bacause there is little evidence

[rando]

Well Done Kev, and thanks again
rando

[rando]

[quote author=kingtin link=1143797596/30#30 date=1144130145]The Environment Likely to be affected by the Fishery

There are approximately 267km2 of seagrass in inshore and estuarine waters of southern Queensland (Hyland, Courtney & Butler 1989) #

Blue green algal blooms have destroyed much of this recently especially in the Deception bay area
rando

Fishing and associated practices that disturb the substrate such as beam trawling may remove benthic habitat and cause changes to the abundance of some species (Zeller 1998). Beam trawling has been shown to remove dead timber and other snags from estuaries (Dredge 1983). Snags support higher fish diversity and are important to a range of estuarine fish of economic importance (e.g. flathead, bream, and moses perch) (Zeller 1998). Snags in estuaries provide habitat values similar to reefs, acting as refugia from predators and cover to ambush prey (Sheaves 1996
cited in Zeller 1998, Robins & Courtney 1998).

However, several studies (Hyland 1988, Coles and Greenwood 1986, Dredge 1983, Gibbs et al 1980) found that the environmental disturbance caused by beam trawling is minor compared to other natural and human induced impacts (e.g. floods, tidal action, dredging, urban and agricultural runoff) (Milward, Morton, Tilbury 1994).

How did they arrive at this conclsion?? what was the comparison used??
studies from as far back as twenty five years (1980) I think might not have relevance to todays fihery

#

[nulla]

Hi kingtin

Great work so far. Keep it up.

[bidkev]

[quote author=kingtin link=1143797596/30#30 date=1144130145]The Environment Likely to be affected by the Fishery

There are approximately 267km2 of seagrass in inshore and estuarine waters of southern Queensland (Hyland, Courtney & Butler 1989)

Blue green algal blooms have destroyed much of this recently especially in the Deception bay area
rando

Fishing and associated practices that disturb the substrate such as beam trawling may remove benthic habitat and cause changes to the abundance of some species (Zeller 1998). Beam trawling has been shown to remove dead timber and other snags from estuaries (Dredge 1983). Snags support higher fish diversity and are important to a range of estuarine fish of economic importance (e.g. flathead, bream, and moses perch) (Zeller 1998). Snags in estuaries provide habitat values similar to reefs, acting as refugia from predators and cover to ambush prey (Sheaves 1996
cited in Zeller 1998, Robins & Courtney 1998).

However, several studies (Hyland 1988, Coles and Greenwood 1986, Dredge 1983, Gibbs et al 1980) found that the environmental disturbance caused by beam trawling is minor compared to other natural and human induced impacts (e.g. floods, tidal action, dredging, urban and agricultural runoff) (Milward, Morton, Tilbury 1994).

How did they arrive at this conclsion?? what was the comparison used??
studies from as far back as twenty five years (1980) I think might not have relevance to todays fihery

Agreed rando and I have no idea with regards to their methodology. Research tends to build on previous research. If a researcher doesn't question the previous research (as you are doing here) then it's likely that any "imperfections" are perpetuated. The older the research, the more it tends to rely on anecdotal evidence due to the lack of legislation requiring statutory logging back then.

Even evidence gathered from log books is suspect ie. It could be argued that skippers, just like everyone else I know, like to put one over on the tax man and will underlog their catch. Some overseas evidence suggests that despite this seeming obvious, it is not likely the case. In order to protect their source of income pros may actually overstate their catch. They have to prove that their catch is sustainable and to show reduced (true?) catches may well lead to further legislation requiring closures, removal of licences etc. They may therefore inflate their figures to protect their jobs.

So it is with the rec sector. Evidence can only be anecdotal here and reccos are the notorious tellers of porky pies

Take this 1997 research of the Pine: Not the Pine River that I have experience of and just how did they arrive at this? No mention of methodology in the research at all

2.71% of Queensland harvest? from I.31% of total Qld trips? That means that the Pine had a 100% more better catch rate than the average rest of Qld. That beggars belief No mention of flathead catch or prawn in the rankings catch despite the fact that some old timers have told me that flathead used to be in abundance 10 to 15 yrs ago and that they used to catch the "odd" snapper Snapper are in the rankings and flathead aren't. So I reieve anecdotal evidence that flathead should be in the rankings but not snapper> The researchers have collected anecdotal evidence that snapper should be in the ratings and flathead shouldn't?

In the 1997 RFISH diary program (not a comprehensive
geographical survey), ranked recreational catch for Pine River
included Whiting, Bream, Winter Whiting, Diver Whiting,
Snapper (Squire), Sand Crab, Catfish Unspecified, Toad Fish,
Flathead, Summer Whiting; Fisheries values (Hays Inlet FHA):
Australian bass, bream, blue salmon, estuary cod, flathead,
garfish, jewfish, luderick, mangrove jack, sea mullet, tailor,
whiting, mud crabs, sand crabs, banana prawns, eastern king
prawns

Total estimated recreational catch (harvest & released) for Pine
River in 1997 was 1,509,755 fish (2.71% of Qld total) from
141,092 trips (1.31% of Qld total). Estimated catch (top 5
species by no.) Whiting 351,799, Bream 230,598, Winter
Whiting 203,028, Diver Whiting 190,131, Snapper (Squire)
127,298

[fisher28]

wow,you must have sore fingers by now kingtin.just some things that ive thought of to add to the discussion.we do remove things from our trawlable areas.some things being disused crab pots,approx half of which still have starving crabs in them which are released,lots of plastics eg chip packets,drink containers,we get a lot of these after rain and balls of disused fishing line.other things that we MOVE are broken off piles,pieces of concrete,wire cable,car parts how they get there im buggered if i know.we move these things to areas that we dont trawl.so hey maybe the removal of these things may actually help the river?disturbing the substrate,have you ever been behind the dredge?and if thats true bout the pine,mate i know where im movin to!!!!

[bidkev]

wow,you must have sore fingers by now kingtin.just some things that ive thought of to add to the discussion.we do remove things from our trawlable areas.some things being disused crab pots,approx half of which still have starving crabs in them which are released,lots of plastics eg chip packets,drink containers,we get a lot of these after rain and balls of disused fishing line.other things that we MOVE are broken off piles,pieces of concrete,wire cable,car parts how they get there im buggered if i know.we move these things to areas that we dont trawl.so hey maybe the removal of these things may actually help the river?disturbing the substrate,have you ever been behind the dredge?and if thats true bout the pine,mate i know where im movin to!!!!

It's mostly cut and paste mate although it does require a fair bit of editing and formatting due to most docs being published in Adobe pdf.

Mate, I can well imagine the crap that you encounter The greenies would love you for it, but the reccos would probably say that you'e moving habitat .....you can't win 'em all mate

Glad to see that you're inputting here as we need to hear both sides of the story.
I've never been behind a dredge and only have to hand what I am researching. To be honest, my own experience of how a trawl looks and works is the otter trawl. I think we're all familiar with those boards hanging on the side of trawlers and up until now, that is how I visualised a trawl. My eyes have been opened

kev

Every truth has two sides; it is well to look at both, before we commit ourselves to either.

[bidkev]

"At present, no specific bycatch monitoring is undertaken in the RITF. Given that there
are no indicator groups or individuals, there is no capacity to detect changes in the
indicator species groups, or to develop appropriate decision rules associated with
bycatch species, beyond the general requirement to reduce bycatch levels in the
entire fishery by 40%."

IOW, There is a general requirement to reduce by-catch by 40% but no (verified) awareness of the composition of the by-catch.

"QB&FP surveillance and scrutiny by recreational fishers and the community living
adjacent to estuaries and inshore sheltered waters where the RITF is located are
considered effective in ensuring a high rate of compliance with those fisheries
regulations enacted to enhance the sustainability of bycatch species (e.g.
observance of closed areas, use of BRDs, etc)."

IOW, there is a high reliance on us (the public) to report (thereby enforce compliance) anything we consider to be an infringement of fisheries legislation.

Impacts on Food Chains

It is generally accepted that a number of estuarine fish are dependent on the macrobenthos (bottom dwelling organisms) as a food source (Hyland 1988). Gibbs, Collins and Collett (1980) conducted a study of the effect of otter trawling in a New South Wales estuary heavily used by both recreational and seasonal, commercial, prawn trawling fishers. The study concluded that otter trawling (without tickler chains) did not cause any observable changes to the macrobenthos.

Tickler chains are usually not fitted to beam trawlers in Moreton Bay, which have either a drop chain hung from the lead (bottom) line or a very thick rope-wrapped 'mud–rope’ as the lead line, so as not to get ‘bogged’

The removal of target and by-product species from the environment through commercial fishing is likely to have an effect on local food chains. Halliday et al (2001) concluded commercial net fishing reduced target fish species relative to areas with no fishing activity, but the abundance of prey and competing predator species did not change significantly in Queensland’s tropical estuaries. Whether these results can be applied to the RITF has not been determined.

[fisher28]

heres something to consider,every day the majority of us drive cars,we all wear tyres out,where in the world do all those microscopic rubber filings go?i guess that they stay on the road or beside the road and get washed down the drain,eventually going to creeks rivers bays then oceans.i wonder if our chain helps move stuff like that on?sounds pretty out there i know,but if you think about it.

[bidkev]

BRD'd and TED.

The angle of the TED is crucial to enable the Turtles, Monsters, Sponges and general large crap to be directed towards the "escape hatch". If it was set perpendicular, it would simply collect unwanted objects at the mouth of the cod end.

The fisheye brd. Commonly favoured because there is hardly any prawn loss and maintenance free. Simply stitch into a hole cut in net.

To date, I don't have figures for the effectiveness of any brd in the beam trawl industry. I'm convinced they don't exist or else my search technigue isn't up to scratch.

[bidkev]

The Bigeye brd

[bidkev]

The radial escape section brd

[bidkev]

Squaremesh codend