STARRY RAY

Amblyraja radiata


Technical report
Author

Marine and Freshwater Research Institute, Iceland

Published

12 June 2026

Key signals

  • Landings have been decreasing substantially.
  • Stock assessment model (SPiCT) shows that the fishing pressure is currently considerably below FMSY.

General information

The starry ray is by far the most abundant elasmobranch species in Icelandic waters, with a widespread distribution across the Icelandic shelf and upper slope at depths ranging from 20 to 1000 m, though it is most commonly found between 30 and 200 m. In Icelandic surveys, individuals rarely exceed 70 cm in length, with the majority measuring between 30 and 50 cm. Reproduction is thought to occur throughout the year, though it peaks during the summer months.

Fishery

The starry ray is abundant in Icelandic waters and is a common bycatch in a variety of fishing gears. Catches are taken all around Iceland but are concentrated within Faxaflói (Figure 1). The increased landings since the 1990s are partly related to increased retention, partly compensating for lower abundance of the D. batis complex. However, fishing regulations were likely responsible for the high proportion of landings from Danish seine during the 1990s. Between 2007 and 2021, landings were mainly reported from the longline fishery (Figure 2). Reported landings increased from 500 tonnes in 2007 to more than 1700 tonnes in 2012. Thereafter, landings showed a steady decline and have not exceeded 250 tonnes since 2022, mainly due to a drastic decline in longline landings (Figure 2), likely driven by a recent regulation permitting the discarding of starry ray (Regulation 1201/2021). A large proportion of landings is destined for local consumption, linked to the Christmas season. This is reflected in the strong seasonality of landings, with the majority reported between September and November each year (Figure 3).

Figure 1: Starry ray. Geographical distribution of the Icelandic fishery since 2017 as reported in logbooks.
Figure 2: Starry ray. Landings by fishing gear since 1990 according to statistics from the Directorate of Fisheries.
Figure 3: Starry ray. Proportion of monthly catch to each year since 2009 according to statistics from the Directorate of Fisheries.

Survey data

Distribution and biomass indices

Starry ray is a frequent catch in MFRI spring (IS-SMB) and autumn surveys (IS-SMH). Seasonal differences in distributional patterns have been noted, with starry ray much less abundant on the shelf in IS-SMH than in IS-SMB. In IS-SMB, starry ray is found at 86% of all stations, but at about 50% of stations in the IS-SMH (Figure 4).

In general, estimates of total biomass of starry ray in IS-SMB show a declining trend over the survey period 1985–2026, with few exceptions, such as the 2022 estimate, which is the highest since 2004 (Figure 5). The biomass index in IS-SMB has decreased from approximately 20000 (average 1985–2000) to 14000 (average 2001-2026). This declining trend is particularly notable for large fish (≥50 cm) during 1993–2008. Since 2010, the index for large fish has remained relatively stable. Estimated biomass of juveniles (≤20 cm) in IS-SMB showed large variation during 2003–2013 but appears stable with an increasing trend over the last decade. In IS-SMH, total biomass is overall lower than in IS-SMB and, in particular, small individuals (≤20 cm) are rarely caught

In MFRI groundfish surveys, starry ray is most abundant in the N and the NW (Figure 6 and Figure 7). In IS-SMB there is a high abundance on the shelf off N-Iceland and in near-shore areas in the south and southeast (Figure 6 a,c,e). In IS-SMH, the main distribution is on the shelf break and starry ray is almost absent from the southern area (Figure 6 b,d,f). Seasonal migration could to some extent explain these seasonal differences in distributional patterns. However, the large seasonal difference in occurrence and catches, especially in the smallest length groups (>30 cm, Figure 6 c,d) could also be partly explained by differences in survey gear (size and weight). Starry ray is a frequent bycatch in several other MFRI surveys. The coastal shrimp survey occurs at various time periods in fjords and near coastal areas and starry ray is widely distributed within the survey areas (Figure 7 a). Similarly, starry ray is a frequent bycatch in the gillnet survey occurring early in April each year (Figure 7 b).

In IS-SMB the highest proportion of catch is taken in areas off NW-, NE- and SE- Iceland and the reduction in biomass is most prominent in these areas. In IS-SMH, the highest proportion of catch is taken in areas off NW- and NE-Iceland; the areas where a reduction in abundance has taken place (Figure 8).

Length distributions from surveys indicate that most specimens are <60 cm . Mean size varies from 36-50 cm depending on surveys (Figure 9). The length distribution is negatively skewed as the proportion of large fish decreases quite abruptly (Figure 9) which is likely due to morphological attributes of the species. Mean length in the spring survey is the lowest in all six surveys and considerably lower than mean length in IS-SMH (overall mean 36 and 40 cm, respectively). The proportion of larger fish decreases quite abruptly after reaching 50 cm (Figure 10 and Figure 11). In IS-SMB, the mean length has decreased over time (Figure 10). On the other hand, in IS-SMH the mean length has varied (from 38 cm to 43 cm) over the period without any specific direction (Figure 11).

The sex ratio is around 1:1 in the spring survey, but in the autumn survey the ratio is skewed towards females (male:female ratio 1:1.3). Males are on average larger than females (39.5 cm and 37.7 cm, respectively). Data on maturity is sampled in the autumn survey allowing for calculations of maturity ogives. Length-at-50%-maturity (L50) is 43.3 cm and 41.9 cm for males and females, respectively (Figure 12). Anecdotal information suggests that starry ray undertakes seasonal migrations related to egg-laying activity. Recently, both surveys have started to sample data on egg case distribution, but trawl survey data may provide useful information on catches of viable skate egg cases and/or nursery grounds.

Figure 4: Starry ray. Frequency (occurrence at % stations) in IS-SMB and IS-SMH.
Figure 5: Starry ray. Total biomass indices (upper left), biomass indices of large individuals (≥50 cm, upper right) and juvenile abundance indices (≤20 cm, lower left), from IS-SMB (black line) and IS-SMH (black dots), with standard deviation.
Figure 6: Starry ray. Spatial distribution in IS-SMB 2026 (a,c,e) and in IS-SMH 2025 (b,d,f). The top panel shows all data, the middle panel shows individuals <30 cm, and the bottom panel shows larger individuals (>50cm).
Figure 7: Starry ray. Spatial distribution in a) shrimp and lobster surveys in 2025 and b) the gillnet survey (IS-SMN) 2026.
Figure 8: Starry ray. Spatial distribution of biomass indices from IS-SMB and IS-SMH.
Figure 9: Starry ray. Length distributions in several MFRI surveys in 2017-2026. All surveys use various form of bottom trawls except the gillnet survey (IS-SMN).
Figure 10: Starry ray. Length distributions in IS-SMB 1985-2026. Mean length (ML, cm) is indicated for each year. Black line is the average mean for the period.
Figure 11: Starry ray. Length distributions in IS-SMH 1996-2025. Mean length (ML, cm) is indicated for each year (upper, right). Black line is the average mean for the period. No survey was conducted in 2011.
Figure 12: Starry ray. Length at maturity. Males: L50= 43.3 cm , L95= 51.8 cm . Females: L50= 41.9 cm, L95=51.5 cm.

Stock assessment

Model and input data

The analytical assessment of starry ray in Icelandic waters is based on recommendations from ICES (2022). The starry ray is considered a data limited stock and follows the ICES framework for such (category 3.1, ICES 2021). A stochastic surplus production model in continuous time (SPiCT; Pedersen and Berg, 2017) is one of the official assessment methods for stocks in this category. The model quantifies observation and process errors and estimates stock status and reference levels with associated confidence intervals. SPiCT estimates MSY based reference levels, which can be used to calculate quantities relevant for fisheries management and ICES recommends using the 35th percentile for all quantities (Mildenberger et al., 2021)

The model synthesizes information from input priors, landings series from 1991 and survey indices from the Icelandic Groundfish survey (IS-SMB) from 1985). Priors used for the model were the intrinsic growth rate, r, and the medium initial biomass depletion, P and the n is fixed at 2 to resemble the Schaefer production curve (ICES 2021) (Table 1).

Table 1: Starry ray. Priors in model
Priors Value Standard.deviation
r log(0.4) 0.04
p log(0.5) 0.25

Results

The output from the model is shown below in Table 2 and Table 3. Model diagnostics are shown in Figure 13, the model results in Figure 14 and the analytical retrospective analysis in Figure 15 Following the checklist for the acceptance of SPiCT model (Mildenberger et al., 2021), one minor issue was found i.e. the Shapiro test indicate some non-normality in the residuals. However, slight violations of these assumptions do not necessarily invalidate model results. Apart from that issue, there are no violations of model assumptions based on one-step ahead residuals, the production curve is realistic (B/K = 0.5) (Figure 13) and the patterns in the retrospective analysis are consistent (Figure 15) . BMSY is estimated at 14.5 kt (Table 3). Annual estimates of B/BMSY and F/FMSY is shown in Table 4.

Table 2: Starry ray. Summary of model results
Parameter Estimate 95% lower CI 95% upper CI Log estimate
alpha 74.130 0.117 47040.884 4.306
beta 0.115 0.001 10.556 −2.163
r 0.117 0.067 0.202 −2.149
rc 0.117 0.067 0.202 −2.149
rold 0.117 0.067 0.202 −2.149
m 846.988 732.848 978.906 6.742
K 29066.488 19108.733 44213.332 10.277
q 0.001 0.001 0.001 −6.934
sdb 0.002 0.000 1.325 −6.172
sdf 0.462 0.326 0.655 −0.772
sdi 0.155 0.123 0.195 −1.866
sdc 0.053 0.001 3.794 −2.934
Table 3: Starry ray. Summary of model results. Estimates for deterministic reference points and stochastic reference points.
Parameter Estimate 95% lower CI 95% upper CI
Bmsyd 14533.244 9554.366 22106.666
Fmsyd 0.058 0.034 0.101
MSYd 846.988 732.848 978.906
Figure 13: Starry ray. SPiCT-model diagnostics.
Figure 14: Starry ray. SPiCT-model results.
Figure 15: Starry ray. Analytical retrospective analysis from SPiCT-model.
Table 4: Starry ray. Estimates of B/Bmsy and F/Fmsy with 95% confidence intervals from the SPiCT model.
Year 95% lower CI B/Bmsy 95% upper CI 95% lower CI F/Fmsy 95% upper CI
1985 0.932 1.223 1.604 0.026 0.274 2.914
1986 0.968 1.258 1.634 0.030 0.271 2.411
1987 1.000 1.292 1.670 0.037 0.265 1.909
1988 1.029 1.325 1.706 0.045 0.256 1.457
1989 1.058 1.357 1.741 0.057 0.247 1.072
1990 1.087 1.388 1.771 0.077 0.237 0.732
1991 1.119 1.418 1.796 0.123 0.228 0.424
1992 1.153 1.446 1.813 0.158 0.255 0.410
1993 1.184 1.470 1.826 0.133 0.225 0.380
1994 1.212 1.492 1.837 0.274 0.452 0.747
1995 1.194 1.454 1.770 0.875 1.424 2.318
1996 1.145 1.384 1.672 0.862 1.365 2.162
1997 1.107 1.331 1.601 0.813 1.279 2.014
1998 1.074 1.287 1.542 0.796 1.245 1.948
1999 1.048 1.253 1.498 0.707 1.105 1.728
2000 1.032 1.232 1.470 0.650 1.017 1.591
2001 1.019 1.214 1.447 0.659 1.043 1.651
2002 0.996 1.187 1.414 0.972 1.516 2.364
2003 0.939 1.122 1.341 1.190 1.840 2.846
2004 0.898 1.077 1.292 0.867 1.342 2.077
2005 0.886 1.065 1.281 0.558 0.870 1.355
2006 0.897 1.078 1.295 0.398 0.625 0.981
2007 0.915 1.099 1.320 0.336 0.532 0.841
2008 0.934 1.122 1.348 0.362 0.576 0.918
2009 0.944 1.135 1.365 0.500 0.790 1.249
2010 0.941 1.133 1.363 0.630 0.996 1.577
2011 0.929 1.119 1.349 0.763 1.219 1.947
2012 0.897 1.083 1.308 1.148 1.812 2.861
2013 0.837 1.015 1.230 1.360 2.137 3.358
2014 0.781 0.954 1.166 1.315 2.074 3.270
2015 0.729 0.901 1.114 1.219 1.931 3.057
2016 0.689 0.863 1.080 1.214 1.928 3.061
2017 0.658 0.835 1.058 0.759 1.209 1.926
2018 0.665 0.847 1.079 0.450 0.760 1.285
2019 0.673 0.862 1.103 0.671 1.097 1.792
2020 0.660 0.854 1.103 0.749 1.227 2.010
2021 0.656 0.855 1.114 0.733 1.225 2.047
2022 0.655 0.861 1.131 0.307 0.515 0.863
2023 0.684 0.901 1.186 0.181 0.308 0.526
2024 0.712 0.941 1.244 0.169 0.285 0.480
2025 0.743 0.985 1.307 0.138 0.239 0.414
2026 0.774 1.029 1.369 0.131 0.254 0.492

Quality of the assessment

More tests, particularly the choice of priori distributions, may be considered. Retrospective pattern is often related to uncertainty about the shape parameter, n, and fixing it or constraining it using priors, often reduces the retrospective patterns. Shorter landing series were used (1991-2026) because the artefact of initial states is possible if catch series start earlier than the index (Maguire and Berg, 2020). Also, reporting on less valued/no valued species such as starry ray was inaccurate in the hayday of landing reports. There is a high seasonality in landings data that doesn’t reflect biological attributes of the species but rather increased demand of the fish in the last quarter of the year (MFRI technical report 2024). This could be explored for estimation of discard rate but discard rates are not known for starry ray in Icelandic waters. Studies elsewhere suggest resilience of this species to discard and thus relatively low discard mortality (Ellis et al. 2017, Knotek et al. 2019). Thus, discard mortality or survival of starry ray in Icelandic waters should be estimated.

References

Ellis, J. R.,McCully Phillips, S. R. and Poisson, F. 2017. A review of capture and post-release mortality of elasmobranchs. Journal of Fish biology. 90(3): 653-722.

ICES (2021). Benchmark Workshop on the development of MSY advice for category 3 stocks using Surplus Production Model in Continuous Time; SPiCT (WKMSYSYSPICT). ICES Scientific Reports. Report. https://doi.org/10.17895/ices.pub.7919

ICES. 2022. ICES technical guidance for harvest control rules and stock assessments for stocks in categories 2 and 3. In Report of ICES Advisory Committee, 2022. ICES Advice 2022, Section 16.4.11. https://doi.org/10.17895/ices.advice.19801564

Knotek, R., Kneebone, J., Sulikowski, J., Curtis, T., Jurek, J., and Mandelman, J. 2019. Utilization of pop-up satellite archival transmitting tags to evaluate thorny skate (Amblyraja radiata) discard mortality in the Gulf of Maine groundfish bottom trawl fishery. ICES Journal of Marine Science. 77(1). 256-266.

Maguire, JJ and Berg CW. 2020. A SPiCT ASSESSMENTS OF THE NORTH ATLANTIC SHORTFIN MAKO SHARK. ICCAT. Collect. Vol. Sci. Pap. ICCAT, 76(10): 156-163.

Mildenberger, T.K., Kokkalis, A., Berg, C.W. 2022. Guidelines for the stochastic production model in continuous time (SPiCT). https://raw.githubusercontent.com/DTUAqua/spict/master/spict/inst/doc/spict_guidelines.pdf

Pedersen, M.W., Berg, C.W., 2017. A stochastic surplus production model in continuous time. Fish and Fisheries, 18: 226-243.