The Atlantic salmon, Salmo salar, is an ecologically and commercially significant fish species that undergoes extensive migrations between freshwater rivers and the open ocean.
The body length of Atlantic salmon grilse (individuals returning to freshwater after one winter at sea) varies between individuals.
The table below shows data on the size of Atlantic salmon caught in one estuary during a scientific tracking study.
| Body length, xxx (mm) | Frequency |
|---|---|
| 400≤x<500400 \le x < 500400≤x<500 | 18 |
| 500≤x<600500 \le x < 600500≤x<600 | 44 |
| 600≤x<700600 \le x < 700600≤x<700 | 96 |
| 700≤x<800700 \le x < 800700≤x<800 | 152 |
| 800≤x<900800 \le x < 900800≤x<900 | 88 |
| 900≤x<1100900 \le x < 1100900≤x<1100 | 36 |
Explain how to construct a suitable histogram to represent these data, specifying the required scales, labels, and the heights and widths of the bars.
Variation in organisms can be caused by genetic and environmental factors. Explain why the data shown in the table indicates that at least some of the variation in body length of the salmon is caused by environmental factors.
Atlantic salmon populations have declined significantly in recent decades, making sustainable management of both wild fisheries and aquaculture critical.
Fish farming (aquaculture) is one potential solution to declining wild fish stocks.
Apart from aquaculture, list three other strategies that national or international authorities could implement to improve the sustainability of commercial marine or river fisheries.
Suggest why international agreements are particularly crucial for achieving sustainable conservation of Atlantic salmon.
