My Lords, I rise to speak briefly in support of the amendment because it provides me with an opportunity to give part two of my lecture on maximum sustainable yields, although I detect that the undergraduate audience is less than enthusiastic about hearing it. However, I want to ask the Minister the following question. The classic textbook on maximum sustainable yield was written by William Ricker in 1975. In it he defined it as
“The largest average catch or yield that can continuously be taken from a stock under existing environmental conditions.”
The three key elements of that definition are “average”, “continuously” and “existing environmental conditions”. I hope the Minister will tell us whether, given that the Government are set on harvesting at MSY—which, as I explained earlier, I think is a mistake—there is a definition in their mind of “average”. To give three possibilities, is it the arithmetic mean, the geometric mean or the harmonic mean?
There must also be something in the Government’s mind about “existing environmental conditions”, which the noble Baroness, Lady Bakewell, already referred to. What does “existing environmental conditions” mean and how will the change in MSY be linked to changing environmental conditions? The Government must also have in their mind a definition of the word “continuously”. Perhaps the Minister could clarify those points for me.