The assessment is based on an UWTV (Underwater TV) survey and has been conducted annually since 2003. The survey is thought to be precise but some uncertainty is present in the estimation of bias. Discarding rates and mean weight in landings are other sources of uncertainty in the calculation of catch options. Indicators from commercial catches (size structure of catches, sex ratio and landings per unit effort), are also taken into consideration. Data and sampling quality are considered to be good (ICES, 2012).
ICES advises under the MSY framework that landings in FU 15 should not exceed 9,300 tons in 2013, based on maintaining a harvest ratio of less than 17.1% (= FMSY proxy) (ICES, 2012).
To protect the stock in this functional unit, management for Nephrops in Subarea VII should be at the functional unit (FU) rather than the entire Subarea VII level. Selectivity of this fishery should also be improved to reduce bycatches of cod, whiting and undersized plaice (ICES, 2012).
Under the new ICES MSY framework, exploitation rates likely to provide long-term yield (and low probability of overfishing) have been examined and proposed as FMSY proxies according to determining factors affecting the biology of the stock and the nature of the fishery. For this stock, ICES concluded that a combined sex Fmax, representing a harvest ratio of 17.1%, was a suitable FMSY proxy, although it is preliminary and may be modified in future assessments. A preliminary MSY B trigger of 3 billion individuals (based on minimum abundance observed) has also been estimated, but no precautionary reference points have been defined for Nephrops (ICES, 2012).
Abundance data from the UWTV surveys indicates that the stock is stable and above MSY Btrigger. The size structure of catches has also remained stable over the fishery’s history. The harvest rate has fluctuated around its MSY reference point FMSY and was estimated to be just above it in 2011. Strong recruitment is ensured by the geography of the functional unit, which retains larvae (ICES, 2012).
The UWTV survey shows a generally stable trend in abundance over the past nine years, and current levels are above MSY Btrigger. Landings showed a rapid increase from the late 1940s to the early 1980s, and since then annual landings have been sustained at around 9,000 tons. Recent harvest rates have fluctuated around FMSY (ICES, 2012).