Calcasieu Menhaden Science

[MathGeek]

With all the oyster and weir talk, folks often miss the importance of menhaden forage to the sport fishery in Calcasieu. In many ways, the closure of the pogey plant (Omega Protein) in late 2013 helped mask the effects of overharvesting oysters.

The graph below shows our analysis of LDWF stock assessment data on gulf menhaden in the first six months of the past five years. Note the increase in menhaden available for your favorite species to eat since the plant closure in late 2013.

OK experts, knowing that we have measured the relative condition factor (plumpness) of specs, reds, drum, and gafftops each spring from 2011 to the present, which predator species will have its plumpness most highly correlated with the pogey stock assessments?

[seachaser250]

Yes.

[jpeff31787]

I'd imagine trout eat more menhaden than any of the other species. I'm not expert though.

[MathGeek]

Originally Posted by jpeff31787

I'd imagine trout eat more menhaden than any of the other species. I'm not expert though.

We have a winner!

Just got that analysis done this afternoon.

More interesting results will be when we get things broken down by length classes and can rank order different prey species for each predator. We'll be able to answer questions like

What are the relative importance of different prey species for different length classes of specks?

[seatrout]

I am still confused on what you are trying to prove from such little data that you are providing on croakers and menhaden???? The only conclusion i can make from this chart is Populations of species that you took samples of... Heck some days the whole lake is covered in menhaden and some days you cant find one. So what can you prove about that??? Statistically you can "attempt" to prove things with incomplete data. Maybe you have looked at too many numbers or too long of time... haha

[MathGeek]

Originally Posted by seatrout

I am still confused on what you are trying to prove from such little data that you are providing on croakers and menhaden???? The only conclusion i can make from this chart is Populations of species that you took samples of... Heck some days the whole lake is covered in menhaden and some days you cant find one. So what can you prove about that??? Statistically you can "attempt" to prove things with incomplete data. Maybe you have looked at too many numbers or too long of time... haha

Prove? Not much. Hypotheses can be supported or refuted, but never really proved.

The posted charts are not from our own data, but they are our calculated catch per unit effort from HUNDREDS of LDWF sampling efforts over many months and locations including many thousands of fish caught. Given the effort and volume of the sampling, the calculated CPUE represent reasonable stock assessments.

It is no accidents the stocks of menhaden went up after the pogey plant closed and Omega Protein stopped harvesting millions of pounds of pogeys.

The data in the graphs just represents the best available LDWF stock assessments. The next step is to correlate the stock assessments of different forage species (prey) with accurate measures of plumpness of several predator species (specs, reds, etc.)

The idea is that the higher the correlation between a predator and prey, the more dependent the predator is on that pray. It is a way to determine which forage species are more strongly used by which predators.

[seatrout]

I give up!!!! My point was that the only information that you are supplying is populations of Prey. How could anyone can form a Hypothesis about anything other than population of prey???? But if you can tell which species of Predator is getting "plump" from that information, you are a GAWL DURN GENIUS!!!

[MathGeek]

Originally Posted by seatrout

I give up!!!! My point was that the only information that you are supplying is populations of Prey. How could anyone can form a Hypothesis about anything other than population of prey???? But if you can tell which species of Predator is getting "plump" from that information, you are a GAWL DURN GENIUS!!!

This is a fishing forum. I was thinking that experienced Big Lake anglers could form educated guesses (that is what a hypothesis is) from their personal experiences and observations. Lots of anglers have educated guesses about the forage preferences of the species they catch.

A hypothesis is formed using preliminary data. Then it is tested using data gathered in a systematic manner independently of the preliminary data used to form the hypothesis. Once you see the data used to test a hypothesis, you are no longer forming a hypothesis, you are drawing inferences or conclusions about whether your hypothesis is correct.

Once you see the data used to test a hypothesis, you are testing it, no longer forming it. (You may need to revise, alter, or reject your initial hypothesis.)

[MathGeek]

The attached graph shows the computed correlations between our original relative condition factor data in the predator species and the LDWF stock assessment data. jpeff correctly predicted trout (SST) would be most strongly dependent on menhaden.

Every species except black drum (BD) shows a significant correlation (p < 0.05). It is notable that there is not a big difference between whether one uses the LDWF stock assessment data over a 90 day or a 180 day interval, which suggests there is ample stock assessment data in a 90 d window to quantify forage relationships.

[TroutSupport.com]

I agree, menhaden is extremely important to all the species except the black drum which primarily forage on bottom, he might caught a slow dumb one though. Trout, reds, and flounder eat a ton of them. So do all the non game species as well. Glad to see that it's benefitting the fish stock in big lake.

[MEM1971]

where are the menhaden in the winter

[MathGeek]

Originally Posted by MEM1971

where are the menhaden in the winter

They grow up and go out into the Gulf. Most of the ones in Big Lake are the young of the year (Age 0).

[TroutSupport.com]

Usually leave in November and are out after the 3rd big tide dumping cold front.