Fixing incompatible array sizes in population dynamics code

For the code below I am getting the error code:

Arrays have incompatible sizes for this operation.

Error in LastName_Assignment5 (line 79)

nt(s, :) = nt(s, :) .* M'; % Element-wise multiplication (note the transpose on M)

% Simulation loop
for t = 1:time_steps
    nt = L * nt;
    for site = 1:site_numbers % Apply Lefkovitch matrix to each site separately
        nt(:, site) = L * nt(:, site);  % Apply to each subpopulation
    end
    % Incorporate Ricker model
    nt = nt .* exp(beta * (1 - sum(nt, 1) ./ K));
    for s = 1:life_stages
        nt(s, :) = nt(s,:) * M;  % Migration applied to each life stage
    end
    record_individuals(t, :, :) = nt;
end 

[Steven Lord]

Without seeing the sizes of the matrices involved in that operation, about the best I think we can do is direct you to the description of what it means for matrices to be compatibly sized in MATLAB.

Note that the code in the error message (which uses element-wise multiplication and the conjugate transpose) is not the same as the code you posted after that (where what I believe to be the corresponding line uses matrix multiplication and no transpose, with a different comment.) Which line of code actually appears on line 79 of LastName_Assignment5?