OFFSHORE SHRIMP

The fishery

Offshore shrimp fishing started in the early 1970’s and takes place in the waters north of Iceland. Catch levels were low during the first decade but increased steadily from 1982 until it peaked in 1997 at 62 thous. tonnes. After 1997, the catch decreased sharply and reached a minimum of 600 tonnes in 2006 (Figure 1). The average annual catch in 2014-2020 was 3300 tonnes and has decreased since 2012 when 7350 tonnes were landed. The landed catch in 2020 was 1960 tonnes, which is the lowest catch since 2006-2008.

In 1988, 152 commercial vessels landed offshore shrimp. The number of commercial shrimp vessels steadily decreased from 1993 to 2006, when only one vessel landed offshore shrimp (Figure 1). The number of vessels increased again until 2013, when 34 vessels landed offshore shrimp, but since 2013 the number of vessels has decreased and in 2023 only 5 vessels landed offshore shrimp.

Figure 1: Offshore northern shrimp. Total catch and number of commercial vessels.

Figure 2: Offshore northern shrimp. Standardized catch per unit effort (CPUE) of shrimp by year, month and trawl size (number of meshes).

Catch per unit effort (CPUE) increased from 1988 to a peak in 1996 but decreased sharply between 1996 and 1999 (Figure 2). CPUE fluctuated between 2001 and 2012 and decreased in the following years. In 2020 and 2021, CPUE increased again to levels seen in 1992 to 1997. CPUE is highest in March but decreases in the summer and is lowest in November and December. CPUE increases with increasing trawl size but is stable at sizes 2500-5000 meshes.

CPUE increases with increasing biomass index (Figure 3). The consistency between CPUE and total biomass index was relatively good between 1989 and 2002 (Figure 3). However, since 2003 the CPUE has indicated better state of the stock compared with the total biomass index. Both indices decreased between 2010 and 2015.

Figure 3: Offhore northern shrimp. On the left: Relationship between standardized catch per unit effort (CPUE) and total biomass index. To the right: Standardized CPUE (solid line, left axis) and total biomass index (broken line, right axis).

The main distribution of the fishery has varied over time (Figure 4). In 1988-2005, the main fishing ground was larger compared with 2006-2020. At that time, a high proportion of the catch was taken from Norðurkantur and around Kolbeinsey (north and northeast of the Vestfirðir peninsula). Since 2006, the main catches were caught in areas north of Skjálfandi and Öxarfjörður fjords and shrimp fishing has not taken place northeast and east of Iceland.

Figure 4: Offshore northern shrimp. Spatial distribution of catch.

Survey data

The annual offshore Icelandic shrimp survey has been conducted since 1988. However, since 2018 the survey has been conducted bi-annually. Originally, the number of stations were about 190, but in 2006 the number of stations was reduced to 92 covering the same area as before with less density of stations. Since 2014 the survey includes 86 fixed stations at depths to 700 m. The survey indices are calculated based on all available stations within the area that has been sampled annually since 1988. All information on sampling procedure can be found in Jónsdóttir 2024. Due to bad weather during the survey in 2024, 6 stations were skipped at the western part of the research area.

The density of shrimp has decreased after 1996, when the biomass index was highest. Since 2004, density has been low east and northeast of Iceland and in 2024 no shrimp was found at several stations in this area (Figure 5).

Figure 5: Offshore northern shrimp. Distribution and abundance in the annual shrimp survey.

Indices

Four indices are used to assess the state of the offshore shrimp stock: total biomass, fishable biomass, female biomass, and juvenile biomass. Juveniles include all individuals equal to and below 13 mm carapace length, while the fishable biomass include all individuals equal to and above 15.5 mm carapace length. The fishable biomass index is used for calculation of the advice. Individuals between 13 and 15.5 mm carapace length are divided between the juvenile and fishable biomass indices. The female biomass includes all females and is defined as the spawning stock biomass.

The total biomass index and the fishable index increased until 1996, after which they declined until 2004 (Figure 6). The indices increased slightly in 2006-2009, but decreased between 2009 and 2011, and have remained relatively stable since then, with the exception of 2015, when they reached historically low levels. The indices have been decreasing since 2018 and in 2024 they were the second lowest since 1988. The fishable index was above the reference level where the state of the stock is considered critical. The fishable index value of 20% of the mean of the mean of the three highest indices (I_lim) is used as a proxy for B_lim. The female index has fluctuated during the study period with a general downward trend. The juvenile index increased from 1988 to 1994. Since then it has decreased, reached historically low levels in 2020 but increased in 2024 which was the second highest value since 2015.

Figure 6: Offshore northern shrimp. Stock biomass index, fishable biomass index, female biomass index and juvenile biomass index. The horizontal line indicates a I_lim which is a proxy for B_lim (20% of the mean of the three highest indices).

Length distribution

Because of slower growth in the offshore area compared with inshore areas, it is difficult to estimate age and hence, cohorts, of offshore shrimp. The number of males has decreased and has been around or below average since 2004. Since 2015 the smallest individuals were missing in the survey but in 2024 higher number of small males were observed (Figure 7).

Figure 7: Offshore northern shrimp. Length distribution. The black line indicates males and the red line females. The grey area is the mean length distribution of both sexes for the whole study period.

Abundance of Atlantic cod

Abundance index of juvenile cod varied without a trend but was very high in 2015 (Figure 8). The abundance index of older cod was very low between 1988 and 1995 but increased in 1996 and since 2003 it has remained high. The cod abundance index has remained high since 2014, with highest values in 2016-2018, and in 2024 the highest cod index since 1988 was observed.

Figure 8: Cod. Abundance indices in the annual offshore shrimp survey. Juveniles are <1 year old (< 16 cm) while older is 1 year old and older.

Temperature

Sea surface temperature during the shrimp survey increased from 1998 to 2003 and has remained at higher levels since then (Figure 9). Bottom temperature increased steadily until 2014 when it peaked at 2°C but has fluctuated between 1.2 and 1.5°C in 2015-2024.

Figure 9: Temperature. Mean surface temperature (red) and bottom temperature (black) in the offshore shrimp area during the shrimp survey.

Management

The Ministry of Food, Agriculture and Fisheries is responsible for management of the Icelandic fisheries and implementation of legislation. The Marine and Freshwater Research Institute (MFRI) first recommended TAC for offshore shrimp in 1987 and the fishery has been managed with TAC since then, except for the quota years 2010/2011 to 2013/2014, when the offshore shrimp fishery was open to all boats without a national TAC. TAC and landed catch has roughly followed the advice given by MFRI (Figure 10).

The quota year from 1 September to 31 August took an effect on 1 September 1991.

Figure 10: Offshore northern shrimp. Comparison of the reliased catches, landed catches and the set TAC. Samanburður á aflamarki, afla og ráðgjöf.

References

Jónsdóttir, I.G. 2024. Handbók um stofnmælingu rækju árið 2024. Kver Hafrannsóknastofnunar, KV2024-007.