And Then There Were None

[Slider]

No we can't blame the pros for the very large rec catches that used to happen, I agree Warti. I remember reading the club results in the paper when bag limits had still to be introduced. Some of the figures were staggering - like - 25 members caught 2600 fish at Jumpinpin or Caloundra. Joe Blogs won the day with 146 bream ..... mind boggling stuff. There was the Recliffe club trip to Moreton not that many years ago where members of a club were caught having left big licks of tailor on the beach and gone home. Fraser was just a slaughterthon at times in the 70s and 80s - blokes taking home hundreds of tailor each and freezing them. Black jew in the Gulf is another good example. But then I've also seen the tonnes of mullet, or dart on the beach here that the pros couldn't find a market for and buried on the beach. Only last year our industrial bins - we don't have rubbish services at Teewah - were filled with dart.

But those days of huge rec catches are gone and the fishery is what it is now. We have bag and size limits and we have the knowledge of how to repair the damage that was done by pros and recs. And we do know that the impact of nets is greater than that of the recs when bag and size limits are in place and which is clearly evidenced by the research done on Lakes Macquarie and Tuross, as well as that in the Southern California Bight.

[choppa]

I can recall the "media" report tho' as well

when the Sunshine Coast (Caloundra) beaches were covered in dead fish,,, (Bycatch)

roughly ,,, 5 years ago

just saying

[Slider]

See the bycatch washed in here generally once per year around Christmas Choppa. Only from Noosa River to Double Island though - nothing serious.

[hooknose]

Bit of a sideline but in reference to the Gladstone pro,s still selling plenty of Barra etc, they arent necessarily catching their fish at Gladstone. I know of one who travelled up to Stanage bay during the Easter break and flogged one of the most productive Barra creeks I have ever seen with no less than 4 nets completely cutting off the creek,he did it on the Sunday(as far as I know highly illegal) he took 200 Barra and hit the creek 3 days in a row, the recs who went up there specifically to fish the spot ran over one of his nets before they realised. The same pro went back to the same creek one week later to repeat the process, the writing is on the wall i,m afraid, apparently he was informed of the location of the spot when one of the locals(after a few too many beers) was boasting that Barra could be caught with any lure at the right times just about every cast. The boys still managed a few Barra on lines and that night the pro came over and gave them a Barra as a peace offering. The local pro,s had never flogged the spot but began to get in on the act soon after, guess we were lucky to have fished it in the old days as I cant see it ever fishing the same in future.

[Slider]

Revisiting the huge recreational hauls and the comparitive impacts of recs vs pros.

There's a fundamental principle of fishery management that has been adopted world-wide. That is, when a stock is reduced by harvesting, their prey species are able to increase their population due to the released predatory pressure, and the remaining fish in the target species have more food and less competition from conspecifics, and are thus able to feed up, grow larger and more fecund, and which maintains the target species population.

No question that the theory is sound and all things being equal, that is the way it should work.

However, it doesn't work that way at all as we are only recently starting to find out. This is because the target species don't just do their normal day to day thing when they have a predator that is so voracious that it can take tens of tonnes at a time. All animals respond to predation pressure with avoidance responses and the avoidance response matches the intensity of the predation threat (threat-sensitive predator avoidance hypothesis).

What fish do, and what all animals do when under heavy predation pressure, is that they avoid the locations where they are most likely to be killed. When nets are shot and tonnes of fish killed, the alarm signals (audible, chemical, visual) alert fish to the presence of the predator and they avoid that location for a while. Over time, when the predator consistently makes appearances in the same location, in this case from the beach at Teewah, the fish begin to avoid the area for longer periods as the costs involved with going there are too great. This takes the fish away from the locations that have sustained their species for millions of years, away from the prey that have sustained their species and away from suitable spawning grounds that have sustained their species. Reduced feeding abilities leads to reduced growth rates which causes reduced fecundity and inappropriate spawning location leads to higher larval mortality.

Any animal under heavy predation pressure, or threat of predation, suffers stress. The stress reduces feeding efficiency which reduces fecundity, and also on its own reduces fecundity which then reduces egg and larval size and strength and thus increased larval mortality. Any animal subjected to prolonged stress associated with predation threat, has reduced fecundity that lasts for the lifetime of that animal and which is passed on to their offspring.

Only nets cause the area avoidance. Only nets cause the inappropriate feeding/breeding locations. Only nets cause migrations to be altered. Only nets cause reduced fecundity. Only nets cause reduced size-at-age.

Recs, on their own do not cause these things. In fact, recs on their own would cause the situation referred to at the top of the page of increased feeding ability due to prey release which leads to bigger fish.

Tailor for instance are known to be taking a more offshore migratory path since the 1970s. Tailor are known to be attaining a smaller size-at-age which is a classic symptom of overfishing in heaps of species around the world. This is an evolutionary change that is in response to fishing pressure. These evolutionary changes do not reverse at the same rate as that which they occurred and cause recovery of overfished stocks, once the fishing pressure has been released, to be very lengthy, and in some situations and species, to not occur at all.

So, it is not just the number of fish killed directly by recs or pros that is a factor in the overall equasion of maintenance of a population. The behavioural responses by the fish to predation threat are critical to the survival of species and this factor is now being recognised. You have to have a fecund stock to maintain populations and nets are reducing fecundity at the same time as they are reducing the stock through excessive harvesting. Recs of course contribute to the harvesting aspect and this of course has to be built into the management of the fishery. But unfortunately, there are a number of things that are not currently being built into the management of fish populations.

All of these factors underscore the success of RFHs in NSW. It is all logical stuff and it is all scientifically documented.

Now that is an extraordinarily brief description of how things do work in fisheries. The entire situation is quite complex as far as all the variables that can occur, the reasons for evolutionary change, the alarm signals and the avoidance responses. I am currently mid way through preparing a document that does deal with all the intricacies of commercial fishing pressure on fish stocks. I can't imagine the document being less than 30000 words and that is just dealing with the pure science and without even touching on any other aspect of fishery management, which are relevent, but were dealt with in the "Proposal for the Creation of Recreational Fishing Havens - Cooloola and Fraser Island", that I released last year and which may still be on the Sunfish Fraser Coast website.

[nigelr]

I wondering Slider, these Commercial fishers must have an incredibly powerful and efficient Lobby group, and not just at a State level.

[Slider]

There's more - a hell of a lot more. I've only scratched the surface.

'Prey release' is the removal of predatory pressure that enables the prey species to build up in numbers - as mentioned. When fishing pressure of the larger, more marketable or more flavoursome species is removed entirely, this enables bait fish populations to climb. Bait fish larvae and adult baitfish feed on plankton and excessive baitfish populations can dent plankton populations and especially in conjunction with a soaring whale population which can be considered to have a similar effect to a commercial fishery. Not to mention the commercial fishery of plankton that supplies the omega 3 tablets that are now mass produced.

To allow baitfish populations to climb too high is counterproductive to marine biodiversity as a result. As spelt out in, I think Shmitz et al (2008), the benefits of fishing pressure release, can only be maximised if some fishing pressure remains to control predator fish populations. This allows baitfish numbers to be controlled and plankton populations to increase which ensures a healthy baitfish population - as alluded to in the first paragraph of the last post re fishery management theory. The balance in the ecosystem is maintained.

If marine parks are designated instead of net free regions that recs can still fish to provide some fishing pressure, then the benefit of the marine park are undone by excessive predator numbers which impact on baitfish numbers which in turn leads to a fall in the predator fish numbers. A cycle like the lynx and snowshoe hare begines to occur with cyclic imbalances that are detrimental to commercial and recreational fisheries on a cyclic basis. There'll be good catches for a few years then the fishery will collapse. There are other aspects to be considered here, such as 'predator release' and subsequent antipredator responses, and they are covered in the Double Island Lagoon netting thread in Saltwater Reports on the last or 2nd last page - I think.

Now, one would think that if the tailor, tuna, mackerel (the pelagic predatory species that feed on baitfish such as anchovy and sardine) populations were to fall, then seabirds such as terns, gannets, albatross, boobies etc would climb because they no longer have to compete with the predatory fish for the baitfish.

Well, it doesn't work that way. The seabirds are all reliant on the tailor, tuna, mackerel etc to herd the baitfish to shallow coastal waters and to the ocean surface where the seabirds can access their food resource. Without the predatory species, the seabirds have to either find alternative food resources or they starve. Terns have increased their dietary intake of insects for example, which provide less nutritious sustenance for the terns and energy levels are reduced.

When nets are shot along the beaches, in the estuaries and near shore environment, the targeted fish species - tailor, tuna, mackerel, dart etc which provide the herding for the terns, avoid the inshore region and move offshore. This causes land-based terns and other seabirds to fly further to feed each time and they can't feed multiple times per day as they have for millions of years. With reduced energy reserves and greater flight distances, there is only one result possible and this is particularly the case for migratory seabirds which many of them are.

Reducing the populations of the predatory fish species as we are doing and particularly so with tailor, is radically compounding the effects of the inshore avoidance of nets. The number of dead juvenile gannets on the beach here this year is a symptom of the lack of tailor. Gannets time their breeding to coincide with the migration of tailor who time their migrations to coincide with the migrations of anchovy and sardine who time their migrations to coincide with the migration of plankton.

You can see how interrealated it all is. Throw out the balance in the ecosystem and trophic cascades begin to occur which reach far further than one could imagine. Algal blooms for instance can occur due to overharvesting of algae consuming shellfish such as scallop, and algae eating fish. We are only beginning to see these trophic cascades start to manifest themselves in our marine ecosystems and they will, with certainty, pick up speed until we have an algae infested ocean that can't sustain mankind.

[Slider]

Yes Nigel, I expect they do. I look forward to taking them on.

[warti]

Hooknose, in reference to the gladstone pros selling fish, i said they were still netting the hot water. Dont believe it if you dont want to, but i know it is still happening. They arent doing it in the daytime like they used to. I have been out a eleven oclock during the week when they have been putting in the river. Maybe they are telling people the catch is from somewhere else. . This was not supposed to be happening yet still it continues. Then the other side whinge about how they are F*&^ed up and cant sell them. So what is exactly happening?

[hooknose]

Warti, i believe you mate doesnt surprise me what they get up to.

[phantomphisher]

I say send the pros to areas where recs can't reach. thousands of k's from the nearest inhabited landmass. There are plenty of fish to be caught out there, you just have to find 'em

[Slider]

If only, Phantomphisher, that was feasible. All that would do though is shift fishing pressure to offshore waters and decimate those regions.

Florida banned all inshore netting in the mid/late 90's that put tens of thousands of people associated with the commercial fishery out of work, and now have enormous schools of mullet that can't be netted, are of no 'direct' benefit to rec fishers and are a fantastic resource that are going to waste. They did, in the process create a multi billion dollar recreational fishery, but this could have been achieved without the banning of all inshore netting.

I talk about a strategic network of net free regions, which in essence is talking about a strategic network of netted regions also. For instance, I would propose that mullet should be netted just inside the mouth of the Noosa River. Netting here means that there would be minimal bycatch, minimal weather influence on commercial efficiencies, minimal net avoidance by mullet and thus minimal impact on reproductive success, minimal impact on other migrating species and minimal impact on recreational fishing. Suitable quotas based on mullet populations and a suitable number of licences to enable viability for each licence holder would need to be established for this to work with maximum benefits. I would like to think that if such a circumstance were permitted to go ahead, then the lakes of the Noosa which are vital nursery areas for a variety of fish and prawn species and aren't very productive commercial fishing grounds, would become net free to compensate. I would also like to think that the mullet would predominantly be directed to human consumption rather than pet food, bait and fertiliser.

Vital to the successful establishment a network of net free regions and a network of netted regions, is an understanding of fish behaviour and the alarm cues of netted fish and their predator avoidance responses which are at the core of fish behaviour and thus successful reproduction. This is the field that I have been most focused on in my research.

I'll provide explanations for how this all works in a little while.

[pescados]

Could not agree more with this post and very well written too.
Thank you.

I can remember catching decent tommy roughs 35 - 40 yrs ago, now if one is lucky one might catch a few 75 mm long.

[phantomphisher]

The only way I could see our fishery prevented from becoming what it is now is if commercial fishos never started using nets in the first place. Those huge rec catches you talk of could have easily sustained a commercial fishery. That way we would still have a thriving commercial and recreational fishery today. If only someone invented a time machine

[Slider]

I'll try to keep this to a manageable length - but it won't be easy and it will mean leaving out substantial amounts of relevent detail. Please pose any questions you might have so that I can provide any necessary details so that it all makes sense.

I spoke of nets spooking fish in the rfl thread. Nets spook fish because nets are the single most devastating predator that a fish has. Fish have evolved antipredator responses to predators and predatory fish have evolved methods to overcome to some degree these antipredator responses.

Alarm cues are integral to all antipredator responses and also to predatory fish location of prey. Alarm cues are in the form of vocalisations, chemical releases and vision. Alarm cues and antipredator responses determine the position of fish in space and time in the marine ecosystem.

When fish are trapped in a net, they emit alarm vocalisations. The slimy stuff on the skin of fish which is called schreckstoff, which is a chemical alarm cue, rubs off the fish through contact with the net and other fish. Startled or alarmed fish in the net also release another chemical alarm cue called a disturbance cue, which is a urinary release of ammonia.

The initial alarm vocalisation of the netted fish alerts fish that are within hearing distance, of the presence of a predator. These fish become startled and release a disturbance cue and exhibit a flight reaction to the predator. Fish further afield than these fish to the net, witness the flight reaction (visual alarm) and also exhibit a flight reaction. It is likely that all of these fish outside the net emit alarm vocalisations as well, but this is yet to be proven.

Schreckstoff is a powerful chemical that lets fish know, through olfactory reception (smell) with certainty that a fish, or fishes of the same species, or other species, has definitely been predated upon (netted). Schreckstoff can remain active for quite some time and alerts fish moving into the region of the fact that a conspecific, or heterospecific, has been predated upon, and they also exhibit a flight reaction. Fish have the ability to determine through the concentration and age of schreckstoff, how many fish have been predated upon and how long ago and also what species of fish has been predated upon.

The end result of the alarm cues and the evolved and learned antipredator responses, is that all fish that are of the same species (conspecific) or of another species that has a history of being netted (same prey guild heterospecific) evacuate the region of the netting and stay away for several days to a week - depending on quite a few variables.

After the period of area avoidance, fish begin to return to the region of the netting, because that is where their food resources are and where they may spawn. But the pros know that they come back and are ready with a net and the process repeats over and over for the period of the netting season.

Over time, fish learn to associate the negative stimuli of alarm cues with the location at which they occur, and they begin to actively avoid the region. To actively avoid the region means alterations to migrations and spatial movements and the circumstances described earlier in this thread of reduced fecundity occur.

I have watched this sequence of events play out year after year at Teewah. That is, until the last 2 years. Previous to the last 2 years, I would be waiting for the return of the fish just as the pros are, so that I could get myself a feed before they are spooked again. But the last 2 years, the fish haven't come back. That is either because they have permanently altered their migrations and spatial movements, or because the fish no longer exist. If they have altered their spatial movements, then the fish are somewhere else. But they aren't somewhere else, because they have disappeared from everywhere else also. Otherwise known as a population collapse.

All of these things combined, ensures that recs do not have any prospect of catching fish in the region of active nets. The affected regions can be very large due to the efficiency of social transmission of information in fishes. For instance, through constant angling surveys over the past 25 years, I have consistently (hundreds of times)found that locations that can be as far as 40kms from the netted site, will not produce fish, even if there has been fish in that location each day, and even up to minutes, prior to a net being shot.