Network Analysis: MTI

[carieh]

From ecopath.org user:Alberto Barausse
This is not precisely a bug according to the standard meaning, but in the MTI analysis discarded groups are positively impacting the fleet that discards them, i.e. I believe they are treated as landings making up the fleet diet matrix. If I am right (this is what clearly appears from my model) I think the routine should be corrected.

Hi guys,
I tried to test this by opening the generic model
-copying the Mixed Trophic Index for the model
-adding discards to small reeffish (they currently do not affect the fishery)

(I added 0.1 t/km2 discards)

-recalculating the MTI

The MTI for reeffish small (xaxis) to fleet 1 (yaxis) changed from 0.0046 to 0.021 so in my opinion the reeffish is having a positive effect on the reeffish?

The MTI for fleet 1 (xaxis) to reeffish small (yaxis)changed from 0.2473
to 0.2473 so no change.

I am not sure why the fish are having a positive effect on the fishery when they are ONLY inserted as discards, perhaps some interactions that are not direct between the two. I am struggling with how to answer this for the user, and I am not sure it is actually a bug, so I will assign to Villy. (sorry Villy)

[villyc]

I've fixed this, Alberto is right. DCCnoDiscard added. A fleet will still have a negative impact on its discards, but the discarded group will not have a positive impact on the fleet

[jeroens]

This bug has not been addressed in EwE5. Needs fixing too?