Student handout 4.4: What is the optimum balance between fish reproduction and harvest?

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The fish stocks produce larger or smaller quantities of new fish, depending on the amount of fish left in the lake after the fishing season is over. What is the fish stock that delivers the largest amount of new fish? The answer to this question gives the key to sustainable fishing.

Takingpart_EN.pdf
Fish stocks at the end of the season in tons

Stock at end of season Recovery (production of new fish) Stock at beginning of new season
80 29 109
85 31 116
90 34 124
95 39 134
96 40 136
97 41 138
98 42 140
99 42 141
100 42 142
101 41 142
102 40 142
103 40 143
104 39 143
105 39 144
110 36 146
115 32 147
120 28 148

This table shows the peak recovery rates that the fish stocks are capable of producing. These recovery rates are ideal for sustainable fishing.