Status Assessment 2021 - Spotted ray

Confidence

Medium

Background Information

The spotted ray was first nominated for inclusion in the OSPAR List of Threatened and/or Declining Species and Habitats in 2001 and it was last assessed in 2010. The key criteria for listing were a decline, sensitivity and rarity within Belgian waters (Region II) where spotted ray was considered to be a common occurrence in the mid-1900s. More contemporary studies in the North Sea (and other parts of Region II) and in other parts of the OSPAR area have shown increases in the relative abundance of spotted ray. Nevertheless, the species remains rare in Belgian, German, Norwegian, and Swedish waters. There is some uncertainty regarding its historical occurrence and abundance in many of these areas.

The status of this species is based on ICES advice to fisheries managers for fishing opportunities. This advice has been integrated into an assessment for conservation purposes.

Condition

Recorded length-at-maturity (L50) for spotted rays measures 50.9 cm in total length (TL) for males and 62.5 cm TL for females (McCully et al. 2012). The observed length range was 10–67 cm TL and 10–76 cm TL for males and females, respectively (McCully et al. 2012). Juveniles and egg cases are often abundant in sheltered inshore nursery areas, e.g. Welsh and eastern Irish coasts (Ellis et al. 2005). Length data for spotted ray in the North Sea, Skagerrak, Kattegat and eastern English Channel, derived from scientific surveys, have shown no trend in the average length over time and are relatively stable in terms of length range. Individual rays up to the expected maximum length have been reported consistently over the time series. The length distribution of spotted ray obtained from a Portuguese survey in Division 9a is also relatively stable over the time-series (ICES 2019b).

Threats and Impacts

The main threat identified in the last assessment was “fisheries mortality (primarily bycatch in commercial fisheries)”. Habitat damage (e.g. due to mobile fishing gears, pollution, eutrophication) was also considered but not evaluated (OSPAR 2010).

A decrease in fishing effort is shown in the Northeast Atlantic from the beginning of the 21st century (e.g. Gascuel et al. 2016; Couce et al. 2020, ICES 2020e). However bycatch remains a threat to the species.

Measures that address key pressures from human activities or conserve the species/habitat

For EU waters, fishing pressure on spotted ray is currently regulated through a Group-TAC which includes all skate and ray species except Raja undulata and those listed as prohibited. The Group-TAC was introduced in 1999 in the North Sea (Division 3.a and Subarea 4) and in 2009 in the eastern English Channel (Division 7.d) and other areas. Recent studies suggest variable at-vessel mortality and discard survival, depending on several factors (e.g. gear type, soaking time, fish size) (Ellis et al. 2018, Schram and Molenaar 2018, Serra-Pereira and Figueiredo 2019). It is possible that this bycaught small-bodied species may be less susceptible to fishing pressure than the large-bodied skates (e.g. Silva et al. 2012), though further studies on discard survival are required.

Conclusion (including management considerations)

The ICES stock-size indicators show an increasing trend for spotted ray stocks within all OSPAR regions where the species is assessed, with OSPAR Region II showing a more pronounced increase as compared to other areas. The IUCN assessment for spotted ray is as a species of “Least Concern” (Nieto et al. 2015). However these indicative trends are relatively recent (i.e. gradual increase overall during the last decade or so) and there is also significant uncertainty (i.e. wide confidence limits) around some stock size estimates. Therefore the conclusion on the species’ status across relevant OSPAR regions is unknown with the exception of Region II in which the upward trend represents a stronger signal over a longer time-frame.

The species remains rare in Belgian, German, Norwegian, and Swedish waters. There is uncertainty regarding its historical occurrence and abundance in many of these areas but there is some evidence that the species was never abundant in the south-western bight of the North Sea (Rijnsdorp et al. 1996, Rogers and Ellis 2000). While there have been improvements in scientific understanding of this species’ biology, knowledge of their life-cycle and population structure remains incomplete.

The ongoing requirement for species-specific reporting of landings has improved the management of skates and rays. In the coming years, attention should be given to the species-specific differences in susceptibility to fishing pressure, and a species-specific approach to management could be considered.

In conclusion, the available information on spotted ray indicates slight improvements in the abundance of the species. However, long-term trends are unsure and identified threats to the species remain. Furthermore, the species fulfils the Texel-Faial criteria of regional importance and sensitivity.

Knowledge Gaps

Although there have been recent studies (e.g. Ellis et al. 2005, 2012, AFBI 2009, Serra-Pereira et al. 2014) on ecologically important habitats for this species, spawning and nursery grounds have yet to be fully delineated. The lack of a defined population structure may also hamper the development of potential spatio-temporal management measures. Therefore, additional tagging programmes (conventional and electronic) and DNA analyses of spotted rays throughout the distributional range could usefully be considered. Further research to examine gear selectivity and discard survival is also required.

Method used

The assessment is based on ICES stock assessments (survey trends).

Sheet reference:

BDC2021/Spotted ray