Soniferous Fish of SEQ

[Matt_Campbell]

Unless area avoidance and suitable stock assessment technologies involving hydrophones is built into every fishery management strategy, then every fishery isn't being managed properly and it is to be expected that there is only one direction for the world's fish stocks to result.

And I can understand that nobody likes being told that they're not doing their jobs properly by individuals that don't have the appropriate university degrees. I would argue however, that it's not appropriate that our fisheries be managed by people who have university degrees, but that don't have the experience in the field to apply the outdated and flawed marine sciences that they have been taught.

Lindsay
I am one of these people you say are applying outdated and flawed marine sciences because of my lack of field experience. I'd be interested to know how stock assessment scientists could include results from hydrophone experiements into a stock assessment?

Also with regard to this statement:

The combination of harvesting fish when in spawning aggregations with that of area avoidance causes fish populations to collapse.

Doesn't area avoidance, initiated by netters, prevent the harvesting of some spawning fish because they avoid the areas in which the netters are operating?

[Lovey80]

Doesn't area avoidance, initiated by netters, prevent the harvesting of some spawning fish because they avoid the areas in which the netters are operating?

I know it was directed at Lindsay but in the mean time I think that Lindsay has covered this before. In effect, although they are prevented from capture because of area avoidance, it also prevents them from being able to spawn at all. Occurrences of fish taking much wider births when entering the sea from the river keeping them from being able to spawn in the shallow gutters. Thats how I understood it anyway.

[Slider]

Lovey, thank you - I think you are absolutely correct in your belief that this area can be a major international hit in drawing fishing related tourists. We have, permit, golden and giant trevs, bonefish, tailor, the tunas and mackerels, billfish and reefies, World Heritage Listed Fraser Island with humpbacks in Hervey Bay and W.H. nominated Cooloola with Noosa at its southern boundary. The recipe is a voluptuous one to say the least.

It does affect you Greg unless you don't want to catch bream in the Passage into the future.

Matt, please don't take my comments as a personal attack on individuals at FQ - if there was better funding for these things then we'd be up with other countries in this regard - experience in the field or not. And there are certainly better people to tell you about this than I. Miles Parsons from Curtain Uni would be the best I know of in Aus. Rodney Rountree is one that I can think of off the top of my head from Canada.
But, to start with, each of our commercial species needs to be recorded on a hydrophone by people who know what they're doing - Ian Tibbets at UQ for instance - and these vocalisations databased so that the vocalisations are recognised when heard during stock/spawning assessments. Fortunately for us, many of these species have already been recorded elsewhere in the world and thus the listing of these species at the beginning of the thread. Hydrophones can be placed in static positions - let's say in Moreton Bay near reef structure and specifically seeking snapper vocalisations over a period of weeks or months. Or they can be mobile and be dropped over the side of the research vessel at any location or point in time that is deemed to achieve a result for a given species being researched - or multiple species. Assessing the success or otherwise of green zones would be an excellent application for static hydrophones. Hydrophones are particularly useful in ascertaining spawning locations and numbers associated with an aggregation. To be able to literally count the fish in a spawning aggregation (in essence) without tagging or sampling is far removed from our current methods of assessment. If you like, I can send you research papers into stock and spawning assessments from mainly the U.S. and Canada that would be able to provide you with much better info than I possibly could. Ping me an email if you're interested - ldines@bigpond.net.au
With regards to how the pros are able to still catch fish when populations are in decline or avoidance mode - I did spell this out in post number 55 of this thread under the title of 'hyperstability'. In essence, the pros realised they were spooking the fish and worked out how to get around the problem by teaming up and shooting nets together in the same location, or at the same time in locations separated by just a few kilomtres then moving on and working the full extent of their license parameters on a cyclic basis over a week or so period (avoidance length of time before fish begin to return to the surf). Then there was the mullet which exit the river oblivious of previous nettings and don't have the opportunity to avoid nets that their conspecifics and heterospecifics had emitted alarm warnings about. I didn't mention in that post, but did so earlier in the thread (post 27) about 'risk assessment' by the fish - they have to feed and breed and can't be in avoidance mode all of the time and is why they return to the surf around 1 week after a successful haul depending on food availability, ocean conditions, location (flushing effect) spawning readiness, haul size/species, avoiding species and age.
However, I also mentioned in post 27, that fish that have arrived at a point of population decline that is very low, will alter their migrations to stay away entirely from nets. This is what tailor have started to do by migrating offshore, which is well documented and is a prelude to population collapse due to spawning in non - conducive locations, but doesn't seem to be worrying anyone. Also indicative of a population that is dangerously low is the smaller size per age of tailor that is also well documented, but doesn't seem to be ringing any alarm bells either. I do find it rather concerning that in 2004, research conducted into tailor found that these things were the case and that pops were at 40% of virgin with recommendations that size limits be increased to 40cm. It was warned in this paper, that if recruitment levels did not improve quickly, that a collapse could well occur and that a total ban on the species would be required with no guarantee that the species would recover at all. Fisheries increased the size limit to 35cm a few years later with no further restrictions on the commercial sector, no further research and no idea about area avoidance and migratory alterations. If it wasn't for NSW banning the commercial take of tailor other than bycatch, I am firmly of the belief that a collapse would have occurred by now. The fact that Qld and NSW have not coordinated their approach to this species which migrates along both our coastlines, is a matter that should raise many an eyebrow.