3.7 Zoogeographical groups of non-commercial fish

Zoogeographical groups of non-commercial fish 2016
Typography
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During the 2016 Barents Sea Ecosystem Survey (BESS) 96 fish species from 33 families were recorded in the both pelagic and bottom catches, some taxa were recorded at genus or family level only (Prokhorova et al., 2017). In the period 2004–2015 a total of 106 species were caught in demersal trawls during the BESS (Johannesen et al., 2017).

All recorded species belonged to the 7 zoogeographic groups: widely distributed, south boreal, boreal, mainly boreal, arctic-boreal, mainly arctic and arctic. Definitions of zoogeographic patterns follow Andriashev and Chernova (1995), with slight modifications by Mecklenburg et al. (2010). Here only bottom-trawl catches of non-commercial fish were used. Both demersal (including bentho-pelagic) and pelagic (neritopelagic, epipelagic, bathypelagic) species were included (Andriashev and Chernova, 1994; Parin, 1968, 1988).

Widely distributed (only ribbon barracudina Arctozenus risso represents this group), south boreal (e.g. whiting Merlangius merlangus, silvery pout Gadiculus argenteus, grey gurnard Eutrigla gurnardus) and boreal (e.g. round skate Rajella fyllae, silvery lightfish Maurolicus muelleri, moustache sculpin Triglops murrayi) species were mostly found in the south western and western part of the survey area where warm Atlantic and Coastal Waters dominates (Figure 3.7.1). The median catch of species from the south boreal and the boreal groups in 2016 (was higher than in 2015 (Table 3.7.1).

Mainly boreal species (e.g. Vahl's eelpout Lycodes gracilis, snakeblenny Lumpenus lampretaeformis, lesser sandeel Ammodytes marinus) were as usual widely distributed over the entire survey area (Figure 3.7.1). The south boreal, boreal and mainly boreal species were widely distributed, most likely due to higher temperature near the bottom throughout the Barents Sea in 2016 compared to 2013–2015. The median catch of species from the mainly boreal group in 2016 was somewhat higher than in 2015) (Table 3.7.1).

Arctic-boreal (e.g. ribbed sculpin Triglops pingelii, Atlantic poacher Leptagonus decagonus), mainly Arctic (e.g. slender eelblenny Lumpenus fabricii, Arctic staghorn sculpin Gymnocanthus tricuspis, variegated snailfish Liparis bathyarcticus) and Arctic (e.g. bigeye sculpin Triglops nybelini, Arctic alligatorfish Aspidophoroides olrikii, pale eelpout Lycodes pallidus) species were distributed west and north off Svalbard/ Spitsbergen, west off Novaya Zemlya Archipelago, in the Pechora Sea area and in the northern part of the survey area (Figure 3.7.1). Species of these groups mostly occur in areas influenced by cold Arctic Water, Spitsbergen Bank Water, Novaya Zemlya Coastal Water and Pechora Coastal Water. The median catch of species from the Arctic-boreal and Arctic group in 2016 were less than in 2015, while the median catch of species from the mainly Arctic group in 2016 was higher than in 2015 (Table 3.7.1).

Figure 3.7.1. Distribution of non-commercial fish species from different zoogeographic groups during the ecosystem survey 2016. Size of circle corresponds to abundance (individuals per nautical mile, only bottom-trawl stations were used, both pelagic and demersal species are included)Figure 3.7.1. Distribution of non-commercial fish species from different zoogeographic groups during the ecosystem survey 2016. Size of circle corresponds to abundance (individuals per nautical mile, only bottom-trawl stations were used, both pelagic and demersal species are included)

 

Table 3.7.1. Median catch (individuals per nautical mile) of non-commercial fish from different zoogeographic groups (only bottom-trawl data were used, both pelagic and demersal species are included).

Table 3.7.1

Temporal development

Since the onset of BESS in2004 we observed a decrease of the area of species from boreal, Arctic-boreal, mainly Arctic and Arctic groups (Figure 3.7.2). Moreover, the median catch of species from mainly Arctic and Arctic groups in the last three years is below the long-term median (Table 3.7.1).

Figure 3.7.2. The area occupied by species of different zoogeographical groups (% of total survey area calculated for each year). Only bottom-trawl catches of non-commercial fish were used, both demersal and pelagic species are includedFigure 3.7.2. The area occupied by species of different zoogeographical groups (% of total survey area calculated for each year). Only bottom-trawl catches of non-commercial fish were used, both demersal and pelagic species are included

The Arctic group of fish is dominated by polar cod (Figure 3.7.3). Excluding polar cod still results in a significant decrease from 2004–2015 in both the number of Arctic fish species per station and the proportion of stations including Arctic fish (Johannesen et al., 2017). The decline was highest in the area around central bank where the proportion of stations with catches of Arctic fish (excluding polar cod) declined from 80% to 40% over the period (Johannesen et al., 2015). There was a significant decline in the proportion of stations with Arctic species over time and the number of Arctic species caught per station.

Figure 3.7.3. Species rank plotted against log abundance of Arctic fish caught at BESS 2004-2015 (from Johannesen et al., 2017).Figure 3.7.3. Species rank plotted against log abundance of Arctic fish caught at BESS 2004-2015 (from Johannesen et al., 2017).

Median catch of species from the south boreal, boreal, mainly boreal and mainly Arctic group in 2016 were higher than in 2015. Catch of species from the Arctic-boreal and Arctic group were less than in 2015 but this might be due to lack of the coverage of the northeastern part of the Barents Sea in 2016.

Overall there has been a decline in the Arctic fish in the Barents Sea since 2004.

Median catch of species from the mainly Arctic and Arctic groups in the last three years was below the mean from 2004–2016 and the area where species from the Arctic-boreal, mainly Arctic and Arctic groups were found decreased. The likely reason for this is the decrease in ice cover and associated Arctic water masses in the Barents Sea.

The area where species from the mainly boreal and south boreal groups were found did not show any trend but the area with boreal species decreased from 2004–2015. We cannot provide any explanation at this point.

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