How timing of fishing seasons impact fish populations

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How timing of fishing seasons impact fish populations

November 18, 2017 - 23:25
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A study highlights how the timing of fishing seasons can influence the fish's chances for spawning, and subsequently impact its population in the future.

Spawning salmon.

Fish that go on long journeys to reach their spawning grounds have many obstacles to contend with. Besides natural ones like predators and rough seas, they also have to contend with man-made ones like polluted rivers, dams that block their paths, etc.

Now, scientists have discovered another man-made obstacle thrown in the fish's path: the timing of our fishing seasons.

A study by the University of Washington (UW) highlights how the timing of fishing seasons might target certain fish species and perhaps alter the diversity and productivity of entire fish populations. It describes how fishing regulations, weather, and the patterns and habits of fishermen may influence the intensity of fishing efforts at certain times, thereby placing more pressure on the fish within a short period.

The university’s press release highlights the situation in the case of salmon: “migration and spawning are timed so that both parents and offspring have the highest chance for survival. Fishing that targets only early or late-arriving fish can, over many generations, reduce the numbers moving and spawning at the time that is most favourable for them biologically.”

As lead author Michael Tillotson said, “We are reducing the ability of fish to find good environmental conditions.”

The UW doctoral student in aquatic and fishery sciences added, “We’re perhaps also reducing the ability of fish to adapt to climate change.” This is because if climate change causes the colder stream water necessary for spawning to emerge later in the autumn, the fish has to choose to risk being fished or to spawn in warmer waters which are unfavourable for egg survival.

According to the researchers, fishing seasons should consider the fish’s biology and the importance of timing, and be responsive to changes. To give salmon and other fish the best chance to adapt to the changing world, the goal of management should be to ensure that sufficient fish spawn and that those that do reflect the diversity of the total population.

They hope that the findings of their study could be used by fisheries managers to devise fishing regulations that would be viable for the future.

“We would like to think creatively about how to integrate climate-driven processes with fishing to be more protective of the populations, and more sustainable in fishing practices in the long run,” said senior author Tom Quinn, UW professor of aquatic and fisheries sciences.

The findings of the study was published in the October issue of Fish and Fisheries journal.

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