Originally Posted by Smalls (Post 780685)

Inferring anything based on a handful of structures doesn't make sense when the lifeform is affected by so many variables. This isn't grass we are talking about, which is affected by a handful of variables that can be quantified or qualified and manipulated quite easily. This is a highly mobile population that is affected by competition, predation, salinity, tides, moon phase, prey abundance, weather, etc. Unless you can eliminate or control all other variables, it is impossible to say that one factor alone contributes to the BMI of a species.

You can control the weirs, but can you control prey abundance, predator abundance, moon, sun, weather, tides, salinity, competition? No. So how do you know that the weirs are responsible, even partly, for the condition of the fish.

My thesis was heavy on statistics, so I know all about what they can and can't tell you. The difference is, I could quantify or qualify ever variable I dealt with. You can't do that here. You miss half the picture because of that. It's not a linear relationship, and will never be a linear relationship.

Weir openings alone do not equal thin fish or thick fish. They may correlate, but again, correlation does not necessarily equal causation.

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Originally Posted by Nickt87 (Post 780670)

They can only gain weight if they are consuming more calories than they are burning. Imagine all the calories they are burning while swimming in that current and eating all that food. That's a lot of tail movement and jaw movement in unison, burning the candle from both ends.

amiright amiright?

Fishing success probably drops off too when the weirs are open. All those fish getting that lock jaw after eating that much.

Originally Posted by Duck Butter (Post 780692)

EXACTLY! That is why I am discrediting his entire hypothesis which was"The more the weirs are open the skinnier the fish are". Its silly to think a weir is the only driving force. There are many many

Originally Posted by MathGeek (Post 780605)

The weir management plan is reasonable and based on sound science. Since they took over management of the weirs in 2012, CPRA has done a very good job managing the weirs according to the management plan. CPRA has been kind enough to share detailed weir opening data with us that has allowed us to compute correlations between the condition of finfish in the lake (specks, redfish, drum, and gafftops) with the weir openings.

The most consistent and strongest correlations between our data on fish condition and any environmental factor we've considered are the NEGATIVE correlations between weir openings and fish condition. In other words, the more the weirs are opened, the thinner the fish are. The attached graph completely disproves the hypothesis that weir closures somehow negatively impact fish condition. The asterisks denote statistical significance at the p < 0.05 level.

Our working hypothesis to explain the NEGATIVE correlations between weir openings and fish condition is based on an analogy with rotating pastures to maximize the forage available for cattle. If the gates between pastures are open all the time, cattle graze all the pastures continuously which results in less production than limiting the pastures that can be grazed and opening the gates occasionally. As applied to the weirs, the idea is that the marsh behind the weirs produces more forage if more separation is allowed to reduce feeding pressure from the finfish until the crop of forage has achieved a larger biomass.

In any event, there is no scientific basis to complain about CPRA's management of the weirs. The biggest issue relating to Big Lake that is within regulatory control is the overharvesting of oysters.

Originally Posted by redchaserron (Post 780701)

MG,

Thanks for posting the information from your study. Is it possible, and has consideration been given to the idea that the difference in condition of the fish during open and closed periods may be due to a change in WHAT they are feeding on? If for example open weirs provided easy pickings on shrimp so the fish avail themselve of it, but when the weirs are closed they feed more on menhaden and finfish, it could be a matter of the fish being thinner when the weirs are open becasue they are taking advantage of easy prey that is lower in nutrients verses eating more nutrient dense food.

Originally Posted by MathGeek (Post 780718)

That could be. But note that our correlations are not between fish condition and whether the weirs were open the day a fish was caught, but rather our correlations are between fish condition and the average weir openings over the 90 day period immediately before each fish was caught.

But thanks for the idea, we need to give more consideration to whether weir closures forces the fish to feed on more nutritional forage.

Originally Posted by MathGeek (Post 780718)

How much influence do you think the seasonality of the opening/closing of the weirs have to do with it. For example, the weirs are more likely to be closed in July - August than in April/May. Obviously there are some seasons where fish will weigh more or less Did you compare same season openings/closures?

Originally Posted by redchaserron (Post 780724)

All of our studies are in the same period each year (late May/early June). Seasonality can affect fish body weight, but we are comparing with the long term Louisiana average weights from the same time of year for each species.

The weir openings are more governed by salinity than season. For example, the average 30 day weir openings over our study period (same time each year) has varied from a low of the weirs only being open 15% of their maximum possible to a high of about 70%.

Weir openings and closures in July-Aug do not impact our study at all, because all our fish are measured in late May/early June and we only consider the weir openings in 30, 60, and 90 day windows before each fish was weighed and measured.

Originally Posted by fisheye (Post 780740)

How are the whooping cranes doing

Originally Posted by B-Stealth (Post 780741)

Doing great, had some WC's show up on my buddies lease in Sweetlake. LDWF found out they arrived, then banned my buddy from hunting his lease until the WC's left the area. :pissed:

Originally Posted by B-Stealth (Post 780741)

Doing great, had some WC's show up on my buddies lease in Sweetlake. LDWF found out they arrived, then banned my buddy from hunting his lease until the WC's left the area. :pissed:

Originally Posted by hunterr77 (Post 780831)

Wow, this thread went from meeting dates, to season dates, to salinity levels, to weirs open and closed, fin fish, thin fish, to how many ducks have you killed, to whooping cranes, you guys sure make work go by on Fridays

Originally Posted by Smalls (Post 780835)

Got a preference on where it goes next? lol!