Blue crab population said to fall again

[BILL H]

NOAA report (http://www.baltimoresun.com/news/local/bay_environment/bal-md.briefs293jul29,0,939690.story)presented in today's Baltimore Sun gives more bad news, or at least confirms the bad news that we already knew. Notes that winter dredge survey is reported to be 90% accurate (whatever that means statistically).:smartisme2:

[paxfish]

It means a whole lot. The WDS has accurately predicted the harvest for nearly 20 years.

When they made the new regs in May, they used the preliminary findings. Now they are published, and it was as bad as they thought. 120 million crabs. Something like 220 million is considered to be the minimum for a healthy stock. And there were over 400 million in the 1990 survey. A fairly steady decline since then (with a few good years and lots of bad years.)

Hopefully, this winter's WDS shows improvement with the new regs.

[BILL H]

It means a whole lot. The WDS has accurately predicted the harvest for nearly 20 years.

When they made the new regs in May, they used the preliminary findings. Now they are published, and it was as bad as they thought. 120 million crabs. Something like 220 million is considered to be the minimum for a healthy stock. And there were over 400 million in the 1990 survey. A fairly steady decline since then (with a few good years and lots of bad years.)

Hopefully, this winter's WDS shows improvement with the new regs.

Pax, although I believe the WDS is an excellent tool, and uses a robust statistical approach, a statement like "90% accurate" means nothing in statistical terms. There is more information that is needed. Something like "the methodology should estimate the population within plus or minus 5%, 90% of the time (substitute correct number for the 5%)". If the number is 50% instead of 5%, then it is not a very good methodology.

Newspapers, and newspaper reporters, are not generally renowned for their statistical sophistication, so I am 90% (plus or minus 3%) sure that the fault is in the reporting, not in the WDS.:D

[Scott McGuire]

BillH,

The winter dredge survey has been used as a tool to predict the following years harvest. I don't think it was intended to be used as a predictor, but since it has matured it has gotten within 10% of the harvest of the following year's harvest. I think this is what they mean by 90% accurate. I'm not defending their choice of words, but I'm sure it was just an effort to make it easier to understand for the average fisherman/crabber.

[BILL H]

Thanks Crow,
Just feeling a bit "crabby" this morning.

[Scott McGuire]

slough it off man...

[paxfish]

Gotcha Bill. I concur.

I read too much into your "whatever that means" statement.

[crabby and son]

I'm sure that with the new restrictions that this winter's survey will be better. How much?....not too much I'm afraid. They waited too long to do something and what they did isn't much. but it is a step in the right direction. It didn't get bad in one year and it won't get better in one year. Gary

[paxfish]

They are pretty resilient - I am hopeful (hope is not a plan, I know). Remember, at 200 million total population, the wise men claim we can take 46% and stay at that level. Remarkably prolific, them crabs. So they are cutting to something like 37% with the new regs.

And, the harvest in October and November has been millions of migrating females. All pregnant. They will be protected in most of October and all of November. And no dredging of females down in Virginny.

We shall see. We must remain vigilant that the new regs don't get overturned. I know there's at least one lawsuit in Virginia disputing the new regs....

We shall see.

[ohbeone]

Like Lynn said during one of the meetings and I'll quote her, "They're like cockroaches."

[Ez2cy]

Here is another video i found today about the state of the blue crabs.

bluecrabs (http://www.youtube.com/watch?v=JCJvnmaPauI)

[JimRockfish]

I trust the report and the science. Just glad that common sense prevailed, hopefully before it's too late. Once the level hits critical (low) mass, just like many other now extinct Bay species, they aint coming back....

[Nummer1]

The WDS cannot be accurate, same areas? different? it is a sampling not a census. As far as predicting the harvest that can be done just as easy without dredging and as we all know there are a lot of unreported catches both comm and recs. From what i've seen so far this year the plan is a success many more littles and females than i've seen in years also lots of nettles, but that could be the water salinity seems like we've had more rain this year. As well the price for #3s has doubled that should help the watermen. N1

[BILL H]

The WDS cannot be accurate, same areas? different? it is a sampling not a census. As far as predicting the harvest that can be done just as easy without dredging and as we all know there are a lot of unreported catches both comm and recs. From what i've seen so far this year the plan is a success many more littles and females than i've seen in years also lots of nettles, but that could be the water salinity seems like we've had more rain this year. As well the price for #3s has doubled that should help the watermen. N1
Stratified random samples (1500). Different areas, randomly selected, distributed across numerous strata (geographic areas), weighted by the area for each strata.

[paxfish]

The WDS cannot be accurate, same areas? different? it is a sampling not a census. N1

Not sure what you're saying here. The WDS is widely regarded as one of the most reliable tools in the fisheries management game. 1500 sampling sites, all over the bay, taken every year, when the crabs are not moving around.

[flattyfrank]

From what i've seen so far this year the plan is a success many more littles and females than i've seen in years

Interesting that you should say that the new management plan has been a success so far, because other than the prohibition of females by recreational crabbers, and many say they never took females anyway, the new restrictions on the comms don't take effect till Sept. The new regs have not had a chance to work yet. And yet, there is a l;arge number of small crabs all over the bay. I'd venture to say that anyone who has crabbed from the patapsco south has been amazed at the number of little crabs. We were told that the juveniles were at the lowest ever according to the winter dredge survey. I'm thinking the survey is not as accurate as DNR proports it to be.

[Black Irish]

The amazing number of little crabs moving into MD very likely had something to do with the new commercial regulations in Virginia that went into effect back in April:

- Add (2) larger cull rings on pots and all rings must be kept open.
- Minimum peeler size went from 3 to 3.25" until 7/15/08 and then 3.5" for the rest of the season.

[josepepper]

It took years to produce this situation, it will take years to improve it although I agree that crabs could rebound quicker than other species in the right circumstances. Also regardless of regulations there will be a drop in the commercial harvest due to fuel, and other increasing cost to the waterman. It's time to focus on runoff, farming and industrial waste. Removing the 10's of thousands of abandoned pots would help as well. In a high tax progressive state like MD the Bay should not be this polluted

[paxfish]

Interesting that you should say that the new management plan has been a success so far, because other than the prohibition of females by recreational crabbers, and many say they never took females anyway, the new restrictions on the comms don't take effect till Sept. The new regs have not had a chance to work yet. And yet, there is a l;arge number of small crabs all over the bay. I'd venture to say that anyone who has crabbed from the patapsco south has been amazed at the number of little crabs. We were told that the juveniles were at the lowest ever according to the winter dredge survey. I'm thinking the survey is not as accurate as DNR proports it to be.

Since recs only take 8 to 10% of the total catch anyway, I agree that the regs have not had a chance to work yet.

The number of little crabs seems unchanged down here on the Pax. There's always a lot of little ones around in June, and perhaps fewer this year.

btw - The WDS is focused on mature females. Mature females have been the best predictor of the coming year's harvest. That survey has predicted the harvest very closely for the last 20 years.

[Scott McGuire]

Folks,

The WDS produces a bay wide picture. The stratified random design mutes the effect of patchy abundance - to achieve a very reliable account of the overall population.

This means that certain locations may have higher abundance, and others may have lower abundance... but overall, you can bet the bay wide total is very close to what the WDS has found.

[flattyfrank]

The amazing number of little crabs moving into MD very likely had something to do with the new commercial regulations in Virginia that went into effect back in April:

- Add (2) larger cull rings on pots and all rings must be kept open.
- Minimum peeler size went from 3 to 3.25" until 7/15/08 and then 3.5" for the rest of the season.

Well, now that's a good point, but it doesn't explain the large number of 4 3/4 -5 inch crabs. Crabs that big weren't hatched this spring. They are crabs that wintered over in the bay, and apparently were missed by the WDS. Now, the huge numbers of 2-4 inch crabs that appear to be everywhere, may be the result of the changes in Virginia, but certainly have nothing to do with new regs in MD. I'm sure that the new regs in MD, when they take effect, and begin to work in conjunction with the changes in VA, will serve to bolster the cyclical crab population in the bay, especially if the environmental conditions at the mouth of the bay when the spawns occur remain favorable for the return of the juveniles to the bay. there could be 500 million in the spawning population, but if conditions are unfavorable for the return of the juveniles to the bay, ie. currents which carry them north or south, recruitment will be low. Conversely, should conditions allow the larvae to flow out and then return to the bay, a relatively small number of spawning females will create a large recruitment. All in all, the number of crabs seen by commercials and recreational crabbers can not be credited to the changes in regulations, so lets not give credit where it is not due

[doublermaster]

thats the dumbest video that ive ever seen and it has nothing to do with crabs other than that its on the chesapeake

good job RETARD

[Black Irish]

Well, now that's a good point, but it doesn't explain the large number of 4 3/4 -5 inch crabs.

A peeler increases approximately 33% in size after shedding. So a 3.25" peeler becomes a 4.3" crab and a 3.5" peeler becomes a 4.7" crab. Add to that the legal crabs that avoided the pots and I think it becomes a pretty good explanation of why there are so many little crabs in MD.

After a second shed (like now), you end up with a bunch of 5.75"-6.25" white crabs. Maybe by the end of August, there will be something worth putting together a trotline to go after. Three weeks ago it was mostly smalls and whites up my way, north of the BB. Reports from the Gunpowder lately still show a bunch of whites. Not worth my effort, culling a lot of junk to catch a half dozen decent fat crabs.

[C-Hawk18]

The WDS has accurately predicted the harvest for nearly 20 years.




Since recs only take 8 to 10% of the total catch anyway,

I always wondered how they come up with harvest numbers for recreational crabbers,
and how the WDS is always so "accurate".

Let's see:

WDS - "Commercial Harvest" (a figure which is tracked) = "Recreational Harvest" (unknown fiqure)

[paxfish]

I always wondered how they come up with harvest numbers for recreational crabbers,
and how the WDS is always so "accurate".

Let's see:

WDS - "Commercial Harvest" (a figure which is tracked) = "Recreational Harvest" (unknown fiqure)

Yes - Fisheries Managers deal with estimates a lot. They try to estimate based on studies. Who know how many crabs are sold unreported? Comm or Rec? Is the rec harvest 8% or 12%? It doesn't matter too much though. The data tells us when to act. The dismal harvest last year was confirmed by the WDS.

The beauty of the WDS is not so much that is says there are 120 million crabs. There might be 140 million. But it doesn't matter. It's utility lies in it's ability to predict the harvest. The WDS has accurately predicted the harvest for nearly 20 years.

It also shows trends. It showed roughly 400 million crabs of spawning age in 1990. It's showing 120 million now. Was the number really 440 million? Maybe. But one thing we know for sure - we're at less than 30% of where we were then. And only half of what is considered to be a sustainable population.

No - I'm not an expert on all things fisheries. But I watch them closely and trying to learn the tools and see how they mesh with my personal experience.