Because we only have two years of experience using these, we don't really know whether they affect fish migration.
Then there's ocean survival. That is a very likely an explanatory factor in how come you can have a relatively good return of jacks and suddenly the adults don't materialize out of that.
We take data of jacks and older-age fish and develop mathematical relationships between these fish that we use to predict the number of fish by age. And in 2004, we actually saw a relatively strong return of jacks, which is the single biggest driving factor in any of our forecasts.
Basically, we looked at a number of different likely culprits that various folks think might be responsible for this shortfall.