Assessment of stock performance on the Ogmore (and other SAP rivers) involves the use of Conservation Limits (CL) to indicate the minimum desirable spawning stock level. CLs are set to maximise the total catch but assume ‘benchmark’ levels of freshwater and marine survival which, on many rivers, are likely to be higher than those which prevail today. As a consequence, the CL is weighted towards protecting the spawning stock and avoidance of over-exploitation by the fisheries. This protection is reinforced by a compliance procedure (below) which ensures that a ‘failure’ is registered if spawning levels fall below the CL in more than 1 year in 5, on average.

The setting of CLs has developed in line with the requirements of ICES (International Council for the Exploration of the Seas) and NASCO (North Atlantic Salmon Conservation Organisation). CLs have been used in salmon management in North America for many years but are a relatively recent development in England and Wales. The Agency is working to improve methods to derive and apply conservation limits and related ‘targets’ to salmon fishery management – a process which is likely to result in refinement of methods used in this plan at some point in the future.

The conservation limit for the Ogmore was based on an estimate of 612, 070 m2 of accessible stream area, which equates to an annual egg deposition 1.42 million eggs (231 eggs 100 m-2). On average, a spawning escapement of 667 salmon will ensure that the conservation limit is met. In assessing performance against the target, annual rod catches coupled with extant exploitation rates have been used.

The trend in egg deposition inevitably reflects the rod catch figures (Figure 4).

Figure 4. Ogmore estimated egg deposition rates 1975 to 2001

Note: Indicates conservation limit failure episodes

Compliance is assessed by examining performance in blocks of three years, and by use of two rules which describe compliance failure. These are:

Rule a. Episodes may last no longer than two years and
Rule b. A clear gap between episodes should be at least two years.

The sequence of egg shortfall or surplus in each three year block determines whether a “pass”, “failure” or “near miss” has occurred. Figure 3 shows the estimated egg deposition for the Ogmore from 1986 to 2001. The red horizontal line indicates failure episodes and shows that since 1986 the Ogmore has failed to comply with the conservation limit. The most recent egg deposition during 2001 was below the CL, with a percentage compliance of 57%.

Salmon numbers in the Ogmore have shown a vast improvement since the early nineties, in line with overall water quality improvements. However, consistent failure to meet the conservation limit sends a clear message that further action is needed to support the Ogmore salmon stocks.