They decrease because the zebra mussel were taking their resources. Leaving them nothing to eat.
<h2>ANSWER:</h2>

<h2>
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DATA:
Force = 50N
Mass of the Body = 1kg
Acceleration = ?
<h2>_____________________________________</h2><h3>SOLUTION:</h3>
By the second law of newton,
F = ma
Rearrange the equation,
a = 
Substitute the variables in the equation,
a = 
OR,
a = 50 m/s^2
<h2>_____________________________________</h2>
Best Regards,
'Borz'
<h3 />
The angle of jaw and type of teeth in each jaw are the main big differences.