Snapper Stocks - Another View

[Jono_SS]

G'day BigE.

Just like everyone else, you are entitled to your opinion. As usual, it is at one extreme of the range, just like when you lamented the missed opportunity to punch every researcher you'd ever encountered.

I'm not quite sure if you're directing your post at me, because I've never fully understood your posts other than realising you feel very strongly you have been shafted in the past and now imagine conspiracy theories in everything the Government tries to do. Maybe the Universities too, I suppose. I'm sorry you (and others) feel that way.

I'm not a fishery manager and can't predict the future so I have no idea what the tipping point would be for snapper. Maybe you could ask the managers yourself at a port meeting near you next month. Or maybe you could have asked the stock assessment scientists at the last lot of meetings at Mooloolaba and Cleveland.

In the meantime, I can think of a couple of examples where TAC for Queensland fisheries have gone up in the past - stout whiting (i.e. trawl whiting) and spanner crabs. I realise the fisheries for these species are primarily commercial, but they still demonstrate that there are opportunities where objective data (rather than subjective opinions) can be used to assess fish stocks and show restrictions can be relaxed.

Is that close to the favour you were asking for?

Jonathan.

[Jono_SS]

I should have also said that the graph I pasted into the earlier post was from the report on the following web page...

http://www.dpi.qld.gov.au/28_15961.htm

[Lovey80]

Big E, your on the money mate. I have said from the start that we have to have a pre-stated Goal/Performance indicator and in your words tipping point. No one can give us this. No one certainly not Jim Groves the grand poohbah has been able to tell us what the performance indicators will be to decide that we have hit our goals and what the response to those "tipping points" will be.

They can't even tell us what measures they intend to enforce on us to "maintain" the biomass once they get to where they want.

I certainly hope they don't think they can just keep banging these models at us to give evidence of improvement or decline.

At the end of the day after all of this is said and done 10-20-30 years time there will still be a large number of people crying foul because there aren't enough fish in the ocean and something must be done about it. When reality is they just need to learn to be a better fisho. They are playing into the hands of the enemy and will certainly regret it when the whole fishery is closed not because of a collapse but because of idealogical reasons. You spend 10-20-30 years crying to the public that the oceans are in danger from Fisho's, feed them the same BS from other countries that actually HAVE raped their waters and just on heresay we will be shut out.

Johno, thanks for the input but you missed my question.

If regardless of how they get their rubbery data or not. Any statistics gurus out there that can bang this into a model and tell us the amount of fish caught between 35-40cm on the below assumptions.

Minimum Size fish taken =1.2kg

Largest fish taken 10kg

AVERAGE fish taken = 1.6kg

total fish taken =400ton

what percentage of fish must be in the 1.2 to 2kg bracket???

[Big Deez]

Any statistics gurus out there that can bang this into a model and tell us the amount of fish caught between 35-40cm

I am not a stats guru but based on the link jono posted:

35cm - 3% (i.e. 34-35 was 6% so say half that)
36-37cm - 12%
38-39cm - 6%
40 - 5.25 (i.e. 40-41cm was 10.5%)

So about 26.25%?

[dayoo]

I am not a stats guru but based on the link jono posted:

35cm - 3% (i.e. 34-35 was 6% so say half that)
36-37cm - 12%
38-39cm - 6%
40 - 5.25 (i.e. 40-41cm was 10.5%)

So about 26.25%?

It may be 26% by numbers but it is less than 14% by weight which is what Fisheries are working with.

Total TAC of 400 tonnes = 250,000 snapper at average weight of 1.6kg.
26% of 250,000 snapper = 65,000 snapper between 35 and 40cm at average weight of about 800 grams or about 52 tonnes.

Remember Fisheries want the estimated tonnage of all three sectors reduced from about 650 tonnes down to 400 tonnes. A total reduction of about 250 tonnes or approx 156,000 snapper at average weight of 1.6kg.
26% of 156,000 snapper between 35 and 40 cm at average weight of 800grams or about 32 tonnes.

So increasing the minimum size from 35cm to 40 cm only accounts for 32 tonnes of the total reduction of 250 tonnes that Fisheries want to achieve.

Just some stats pulled from my notes from the RRFF working group meetings.

Cheers
Barry

[honda900]

This was posted in another thread, and is a direct quote from the 2009 snapper assesment document.. Which subsequently relies on the phone poll result documents, all of these documents form the basis of the RIS, there are references to all in the document or from one document to the next.

It is important to understand how DEEDI / Fisheries, manipulated the results to their own end.. then published it.. Apparantly it's ok to fudge the figures when the numbers dont add up.. Just add variables to the formula..

· This stock assessment used a series of statistical analyses (generalised linear modelling, SALSA and SSRA population Models) to investigate to what extent, if any, the stock is overfished.
· Catch rates from the commercial sector were stable over time, appearing to indicate a low impact of fishing.
· Howerver, there are concerns that the commercial data were hyperstable (catch rates can remain stable while abundance is declining), and this concern is supported by charter data and two recreational data sources, which all showed consistent significant declines.
· Model uncertainties
· Although the best available data were used to determine the status of the stock, there was an inherent level of uncertainty associated with the data and model assumptions. Major levels of uncertainty exist in the key biological parameters of natural mortality and stock–recruitment, as well as in the fisheries data of the historical and recreational catches;

This one is brilliant..

· However, if there is a significant level of stochastic variation on top of a presumed deterministic stock-recruitment relationship (one level of stock size gives rise to a range of recruitment levels (then this interpretation is not the only one possible. A high proportion of smaller animals relative to larger ones could also be due to the appearance of numerous strong recruitment years. This confounding is particularly vexing because the possible interpretations are quite divergent – one of high fishing mortality and the other low fishing mortality and strong recruitment.

In order to remove this confounding it would be necessary to incorporate recruitment variation into the estimation process for the stock mode. One way to do this would be to estimate a recruitment ‘anomaly’ for each year of the fishery (for a concise summary of this topic and other approaches see Walters & Martell (2004, p. 96)). Preliminary runs of the model using this estimation approach ended up with very large recruitment anomalies estimated for the years 1993/94. The estimation process clearly preferred the strong recruitment interpretation to the high fishing mortality interpretation. The problem with this estimation is that we only had ‘snapshots’ of composition information (one in 1994/95 and one in 2006/07) to inform the model, not a time series. Time constraints prevented a detailed investigation of this issue; however, the following points are pertinent

Sensitivity to uncertain catch history

· The use of boat registration information and Fish Board records to construct historical changes in harvest has been criticised as a source of model bias. Likewise, there is uncertainty about the accuracy of recreational harvest estimates.


Regards
Honda.

[Lovey80]

It may be 26% by numbers but it is less than 14% by weight which is what Fisheries are working with.

Total TAC of 400 tonnes = 250,000 snapper at average weight of 1.6kg.
26% of 250,000 snapper = 65,000 snapper between 35 and 40cm at average weight of about 800 grams or about 52 tonnes.


Remember Fisheries want the estimated tonnage of all three sectors reduced from about 650 tonnes down to 400 tonnes. A total reduction of about 250 tonnes or approx 156,000 snapper at average weight of 1.6kg.
26% of 156,000 snapper between 35 and 40 cm at average weight of 800grams or about 32 tonnes.

So increasing the minimum size from 35cm to 40 cm only accounts for 32 tonnes of the total reduction of 250 tonnes that Fisheries want to achieve.

Just some stats pulled from my notes from the RRFF working group meetings.

Cheers
Barry

Thanks Barry,

Although it proves their point at 13-14%, raising the size limit to 40cm for all sectors should actually account for 84.5t of the 250t they want to reduce the take by.

Current take: 650t @ 1.6kg average = 406,250 fish

26% of 406,250 Fish is 105,625 Fish

105,625 Fish @ 0.8kg average is 84.5t Say a 85t Reduction.

Even though these figures are all based on Rubbery Science, I would still rather see a 40cm minimum size increase brought in to "stop us hitting our TAC too early" than a one sided lock out.

OK say there is only a 14% reduction by lifting to 40cm, by giving Rec Anglers a 6 week closure that is only reducing potential effort by 11-12% of time and ONLY to 1 sector...... Just in case! That doesn't also take into consideration allowing recs only 1 trophy over 60-70cm in the rebuild period also.

Just my thoughts

[peterbo3]

Maybe we need to peek at this. Most discussion has been about the "science" DPI have used. In SA that "science" is looking a bit shaky. Of course, it could be just a statistical blip in one of the most regulated & studied fisheries in the world.
http://www.abc.net.au/news/stories/2...section=justin

[scifly]

Hi All

I have been reluctant to get too involved with the snapper issue but given the limited options in the RIS, I have no choice. Unfortunately, this is no longer an issue about the science and debating the survey methods and analysis used is wasting time and effort.

Yes, I do know what I am talking about, having been intimately involved in the diary program and the boat ramp survey. It is impossible to convince people that don't trust survey programs so I am not about to try. Yes, there is a failing in communicating about survey methods and how they work and so far, the explanations from FQ have not been great.

The important issue now to consider is the options presented in the RIS and what they mean. If you are opposed to all the options and dont think any will work (Option 4 is unlikely to be supported by FQ), you need to work with your local MPs. Brief them on the issue and raise their awareness.

FQ and the minister have decided to make this a political issue. The independent reviews and for that matter, the original stock assessment reports consider it plausible that Snapper are either overfished or fully fished.

Unfortunately, FQ and the minister have decided to focus on the 1st half of the sentence and will suggest that they are acting according to the Precautionary Principle.

This may be true but it doesnt excuse the inaccuracies and apparently baseless assumptions in the RIS. For this reason alone, fishers should be raising concerns about the quality of the RIS and sending FQ back to the drawing board.

Just my personal opinion
Len

PS - Yes, I have concerns about some of the methods in the assessment and elements of the data and these concerns were passed on to FQ.