Proposed calculation methodology of "Harvestable Surplus" is dangerously flawed

"The harvestable surplus will be calculated by Marine Scotland Science using available information on the numbers of returning salmon over the last available 5 years"

Using only the last 5 years data to calculate a "Harvest Surplus" is dangerously flawed and will potentially produce negative conservation results.

Take for example the River Carron.

"Annual catches of Atlantic salmon on the River Carron between 1952 and 2013 varied from 5 to 417. Based on a 5 year rolling average catches have changed from ~35 - 70 between 1956 and 1976 to ~130 - 155 between 1979 and 1990, dropping to ~80 - 95 from 1991to1995, with a progressive decline to historical lows of <15 fish between1999 and 2003. There was then a rapid increase to >300 in 2012, with all values since 2008 representing historical highs (>200). " **

If, as is the case with many other West coast rivers negatively affected by aquaculture and other factors, there had been no been restoration programme, and catches remained at the historic lows of 1999-2003, basing a harvestable surplus on this 5 year average would be clearly flawed and would effectively ensure that the numbers of returning Salmon would remain at these levels. (assuming that everything above these levels would be harvestable and would be harvested)

Surley a better definition of Harvestable Surplus, would be the number of fish over and above the number required to populate the river system to its maximum potential of fry and parr. The number of returing fish from this population of juveniles can only ever be a reflection of mortality outside the river limits. 

**Source: River Carron Restoration Project Project Report Executive summary vii 03 February 2015 

Why the contribution is important

This is important because we cannot use the last 5 years of data throughout Scotland to set an acceptable base for wild Salmon populations. We would effectvely be creating a new normal. 

We should be attempting to restore wild populations to historical maximums, not pegging them to contemporary minimums.

by csmith on July 25, 2015 at 10:22AM

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