The fishery
Shrimp fishing started in Arnarfjörður in the 1930‘s. Between 1960 and 2015, the catch in Arnarfjörður fluctuated between 100 and 850 tonnes, except in the quota years 2005/2006 and 2006/2007 (Figure 1) when no fishing was allowed due to low shrimp biomass index in the area. Since 1994, the catch has decreased steadily and was only 116 tonnes in the quota year 2016/2017. No fishing was allowed in 2017/2018 due to a low shrimp biomass index. Since 2018, the catch ranged between 140 and 200 tonnes. Catch per unit effort (CPUE) was relatively stable between 1960 and 1985, with a sharp increase in the following decade. Since 2000, CPUE has increased steadily, mainly due to increased density of shrimp within the innermost part of the fjord.
The distribution of the fishery has varied over time (Figure 2). The main fishing area has decreased and since 2009 most of the catch has been taken from a relatively small area within the innermost part of Arnarfjörður.
Survey data
The annual Icelandic shrimp survey has been conducted since 1988 in Arnarfjörður in the autumn. The 2022 survey was conducted on 21 September and 14-16 October and included 22 fixed stations at depths of 52-97 m. Information on sampling procedure can be found in the manual ‘Handbók um stofnmælingu rækju 2024’ (Jónsdóttir 2024).
In 1988–1996, shrimp was found throughout the whole fjord (Figure 3). In 1997, the distributional area decreased and since 2005 shrimp has only been found within a small area at the innermost part of the fjord. These changes in distribution are thought to be mainly due to increased abundance of cod and haddock in the outer part of the fjord. In 2024, northern shrimp was only found deep in Arnarfjorður (Borgarfjordur, the inner and northern fjord within Arnarfjordur).
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 stock and fishable indices were relatively stable until 2005 when they decreased sharply (Figure 4). Since 2006 the indices were again relatively stable but at a lower level compared with before. However, in 2016 the indices decreased, and the fishable index was slightly above the reference level where the state of the stock is considered critical. The fishable index value of 20% of the mean of the three highest indices (Ilim) is used as a proxy for Blim. In 2017 the fishable index was at historically low levels and below the reference level. In 2018-2024, the fishable biomass index was just above the reference level. The juvenile index was low in 2016-2023 but increased considerably in 2024.
Length distribution
Since 2011, the mean length of females has been lower and female maximum length has not reached the same length as before and since 2016, the large individual females were not found in Arnarfjörður (Figure 5). In 2024, the number of small males were higher compared to last years.
Abundance of Atlantic cod and haddock
The abundance of 0-group juveniles has fluctuated without a trend throughout the study period. In 2024, the abundance of 0-group cod and haddock was low (Figure 6). The haddock abundance index (1 year and older) increased from 1994 to 2008 but decreased to a low level in 2014 and has since then fluctuated with increasing trend (Figure 6). The number of haddock 1 year and older was though in 2020-2024 the highest values since 2011. The abundance of cod (1 year and older) has fluctuated without a trend but in 2024 the abundance was the third highest in the study period.
Temperature
Sea surface temperature during the shrimp survey increased from 1998 to 2003 and has remained at higher levels since then (Figure 7). 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.
Management
The Ministry of Food, Agriculture and Fisheries is responsible for management of the Icelandic fisheries and implementation of legislation. The fishing season was from early winter (following the annual Icelandic shrimp survey in September/October) until 30 April but in 2017 it was changed to 31 August. TAC and landed catch has roughly followed the advice given by MFRI (Figure 8).
References
Jónsdóttir, I.G. 2024. Handbók um stofnmælingu rækju árið 2024. Kver Hafrannsóknastofnunar, KV2024-007.