European Regional Assessment: LC

Gadus morhua is restricted to the northern Atlantic Ocean and adjacent waters of the Arctic Ocean. It is found to depths of 600 m. Within the European Regional Assessment Zone this species is managed across 13 stocks. Age of first maturity, longevity and estimates of generation length are variable across the region and have generally decreased over time. This decrease has been attributed to high fishing pressure. Recent estimates of the age at first maturity range from 2 to 7 years, while longevity ranges from 10 to 20 years or more. In 2010, weighted average generation length for the Arctic, Norwegian coastal and North Sea stocks was 6.9 years was used by the Norwegian National Redlist project to assess this species. This value was used to assess this species against Criterion A at the European Regional Level. Population trends for G. morhua were examined over a period of 3 generation lengths or roughly 21 years. Although this species has undergone significant historical population declines, over the last 10 to 20 years available estimates for SSB summed across 8 stocks in the region show relatively stable trends with a recent increase in SSB. This recent increase in SSB as been attributed to the increase in abundance of the largest stock, the Arcto-Norwegian cod. SSB estimates are not available for all G. morhua stocks in the region. The North Sea stock has shown recent signs of recovery from historically low biomass levels.Some stocks, such as Faroe Plateau, Faroe Bank (closed due to low biomass), West of Scotland, Irish Sea (closed due to low biomass), Norwegian Coastal Cod and Kattegat have failed to recover from historical population declines. Overall, G. morhua is well researched and managed throughout its range in the northeast Atlantic. Therefore, Gadus morhua is listed as Least Concern. 

Gadus morhua is restricted to the North Atlantic Ocean and adjacent waters of the Arctic Ocean. Gadus morhua is found from Greenland south to Cape Hatteras in the western Atlantic Ocean. In the northeastern Atlantic, G. morhua is known from Svalbard and the Barents Sea south to the British Isles and the northern Bay of Biscay, including the region around Bear Island (Cohen et al. 1990). The distribution extends for variable distances to the north, depending upon climate trends. It is found to depths of 600 m.

All of the Northeastern Atlantic stocks, with the exception of the Celtic Sea stock have suffered prolonged periods of decline since 1970 extending into the mid-2000s (ICES 2006). Simplified estimates of the proportion of cod biomass remaining in the North Atlantic range from 0.1 to 1% of virgin biomass across 21 cod stocks (Myers and Worm 2005), however these estimates of virgin biomass are simplistic and may not have taken account of environmental and foodweb constraints ( pers. comm. 2014). However, in the mid 2000s and early 2010s, some Eastern Atlantic stocks have exhibited reversals in this declining trend. 

The following 13 stocks are recognized in European marine assessment region: Northeastern Arctic Cod, Norwegian Coastal Cod, Iceland, Eastern Baltic, Western Baltic, Kattegat, North Sea (including Eastern Channel and Skagerrak), Irish Sea, Rockall, West of Scotland, Celtic Sea, Faroe Bank, Faroe plateau.

Cod stocks in the region range from fully exploited to depleted. Total Biomass estimates for cod stocks (cod-arct; cod-farp; cod-iceg; cod2532; cod7e-k; cod-scrow; cod-347d)  over the last 30 years (1981 to 2011, a time interval where data for all stocks is available) show an overall trend of gradual decrease from 4366872 tonnes in 1981 to a low of 236711 tonnes in 1999.  In the subsequent 12 years, estimates of Total Biomass increased to 5222031 tonnes in 2011. The increase in the total and standing stock biomass of North East Arctic Cod, a single management unit which is distributed along the Norwegian coast and in the oceanic regions of the Barents Sea – Spitsbergen area, drives the recent increase in total biomass in the Northeastern Atlantic. Overall, over the past 10 to 20 years, total SSB summed across all stocks in the region are relatively stable, and recently increasing (ICES Database, ICES Advice 2013).

However, it is important to note that in the Northeastern Atlantic, stocks which are outside safe biological limits are Faroe Plateau, Faroe Bank (closed due to low biomass), West of Scotland, Irish Sea (closed due to low biomass), North Sea, Norwegian Coastal Cod and Kattegat.

In the Eastern Baltic, the level of recruitment has been stable, but at lower levels over the past 20 years (1990-2010) compared to prior years. In the Eastern Baltic, this species has lost two-thirds of its spawning area due to eutrophication and lack of saline water. However, the SSB has been rising over the past 10 years, and current mortality is below Fmsy.

Declines in age and size at maturity in many stocks (in particular: Arcto-Norwegian Cod, S. Labrador, S. Gulf of St Lawrence) have been attributed to genetic responses to the selective pressures of high fishing mortality. Declines in recruitment rates in some stocks have been attributed to declines in age and size at maturity in some stocks.

Global/species-level information
Global landings are declared from the following FAO fishing regions: NE Atlantic, NW Atlantic, Arctic Sea. The overall trend in declared landings is one of continual increase to a peak of 3,939,642 tonnes in 1970 followed by a continual decrease in global declared landings to minimum of 769,317 - a decline of 63% - in 2008. Since 2008, landings have increased slightly, to 1,049,666 tonnes, the majority of which (96%) originate in the Northeast Atlantic Fishing Zone. Global landings of G. morhua peaked in 1970 at 3,939,642 tonnes; since then, landings have declined by 73%, to 1,049,666 tonnes in 2011. Over the last 30 years (1981-2011), landings have declined by 51%; over the last 20 years, global landings declined by 46% (FishStatJ - accessed July 2013). Landing statistics do not take into account decreasing in fishing effort. FAO also recognizes several sub-species: G. morhua callarias (Baltic Sea), G. morhua kildinensis (restricted to a small lake on an island near the entrance to Kola Bay) and G. morhua morhua natio hiemalis (Kandalaksha Bay) (Cohen 2009).

Population and stock structure
The Atlantic Cod, G. morhua, is recognized as a single, valid taxonomic unit. However, there is substantial population structure and variability in morphology, ecology and behavior within this species. Additionally, this species have undergone a recent and rapid evolution in response to the fisheries-induced depletion of 99 percent of Canadian populations. This fisheries-induced evolution has been hypthesized to negatively affect the persistence and recovery potential of depleted populations (Kuparinen and Hutchings 2012).

There is a significant relationship between gene flow and geographic distance in G. morhua, both across its entire range and at smaller geographic scales. It is proposed that, after an initial colonization period gene flow has slowed considerably among extant populations (Pogson et al. 2001).  On a North-Atlantic wide scale, genetic studies utilizing RFLP, mini- and microsatellite markers support the genetic distinctness of Eastern and Western Atlantic populations of G. morhua. These markers also support the distinctness of populations in the Barents Sea from other populations in the Northeastern Atlantic (Bradbury et al. 2012). In the Northeastern Atlantic, genetic differentiation has been found at various spatial scales. Major populations include the NE Arctic, Norwegian coastal, North Sea, and Baltic cod stocks. Cod in Iceland may be sub-divided into at least two populations, but are managed as a single unit (Jónsdóttir et al. 2007, Reiss et al. 2009). Sub-population structure is evident in the North Sea stock, and additional fine-scale microgeographic structure among fjords throughout the region has also been suggested, however the temporal stability of this structure is poorly understood (Reiss et al. 2009). In contrast to cod stocks in the western Atlantic, Northeastern Atlantic stocks do not share patterns in increase and decline in biomass, and all stocks are in areas where the average annual bottom temperature exceeds 4C (ICES WKDRCS Report 2006).

Stock-specific information in the Northeastern Atlantic
Arcto-Norwegian Cod
There are several similarities between stocks in the Western Atlantic and the Arcto-Norwegian Cod Stock. Of all eastern Atlantic Cod stocks, the Arcto-Norwegian Cod occupies the coldest bottom average temperature, which hovers around 4C (ICES 2005). The effects of temperature variability are generally greater at low than at high temperatures, and changes in mean weight-at-age are generally smaller in stocks found in warmer waters (ICES WKDRC5 Report 2006). There is evidence for a prolonged decrease in the mean age of this stock which has accompanied the intensification of this fishery (Ottersen 2008), and a sharp drop in the proportion of repeat spawners (Ottersen et al. 2006 references in ICES WKDRCS Report 2006). An investigation by Brander found that for 10 of 15 stocks investigated, prolonged periods of decline in biomass were preceded or coincided with declines in mean weight-at-age (in ICES WKDRCS Report 2006).

Total biomass estimates for Arcto-Norwegian Cod are available from 1946 onwards; it is worth noting that the current total biomass is the third-highest estimate in this time series and is 88% of the 1946 biomass; Spawning Stock Biomass has increased throughout the time series, with the highest levels recorded in 2011. The age of 50% maturity for this stock is between 6 to 7 years old; spawning stock biomass for this species as a proportion of total biomass has increased over time to a high of 50% in 2011. F_current is below F_msy, B_current is above B_lim. It is worth noting that there is evidence of genetic structure between Norwegian Coastal Cod and the more migratory Arctic Cod stock (summarized in Bradbury et al. 2012) although biomass data may be aggregated in the ICES Stock Assessment Database. 

Iceland/Greenland
Stocks in Iceland/Greenland have contributed an average of 24% to the total biomass, has exhibited a steady decline from 1241870 tonnes in 1981 to a low of 550369 tonnes with fluctuations and some sign of biomass increase from 1995 on-wards, to 944459 tonnes in 2011. In 2013, the Icelandic stock was considered to be at full reproductive capacity; F_current<F_msy, and fishing mortality has been steadily decreasing since the early 2000s. SSB is increasing, and the stock is considered to be at full reproductive capacity, although productivity is relatively low. Standing Stock Biomass is expected to increase by 14% in 2014 under the current management regime. (ICES Advice 2013).The Inshore Greenland Cod is a data-limited stock, however qualitative evaluations are that Biomass is increasing, and recruitment is good. Cod in Greenland live close to the distributional limit, which renders the population vulnerable to environmental fluctuations. Catches are increasing (ICES Advice 2013). ICES advises that no offshore fishery should take place in order to improve the likelihood of establishing offshore spawning stocks in West and East Greenland (ICES Advice 2013).

Baltic Sea/Kattegat
It has been hypothesized that for cod in the Baltic Sea, low stock biomass has increased the relative importance of factors governing dynamics and productivity. Predation via pelagic fish on eggs and larvae of cod may be may be sources of high predation mortality. Without changes in environmental conditions favoring better recruitment, it is unlikely that cod in the Baltic Sea will experience any substantial increases in biomass (WKDRCS Report 2006). 

Cod in Subdivisions 22-24 (Western Baltic Sea) - F_current>F_msy; B_current>B_lim After dropping precipitously in the early 1990s, SSB increased and has undergone fluctuations (in the early 1980s, SSB fluctuates around 50t tonnes; 2012 estimates fluctuate around 40t tonnes, the overall trend is an increase in biomass over the last 21 years. A management plan for this stock was agreed upon by the EU which aims for a reduction in fishing mortality by 10% each year until target mortality is reached; however, current F is still above management goals.

Cod in subdivisions 25-32 (Eastern Baltic Sea - Cod2532 in database) - This stock has exhibited precipitous declines in SSB since peaking in the mid 1980s.  slope of linear trend line: -23485; 69% decline from 1981 to 2011: total biomass in 1981: 948216 t; 2011: 657693). F_current<F_msy; B_current>B_lim since 2008 (ICES Advice 2013). 

Cod in Division IIIa East (Kattegat) - This is a genetically-distinct stock, separate from the North Sea (André et al. in prep.). ICES advises that there should be no directed fisheries and by-catch and discards should be minimized.

Cod in Subarea IV (North Sea) and Divisions (VIId) (Eastern Channel) and IIIa West (Skagerrak) - A continuing reduction in Fishing mortality, which began in the late 1990s and has continued until 2013, has led to a slight improvement in the status of this stock over the last few years; The stock SSB has increased from the historical low in 2006 and is predicted to further increase. However, recruitment is still poor. F_MSYcurrent> F_MSY; B_current>B_lim (ICES Advice 2013).

Celtic Sea Cod (Cod in Divisions VIIe-k) - F_msy is at target (0.4), but was well above target in recent years; B_current> B_lim in 2012. This cod stock lives at the highest average temperature, with the highest growth rate, condition and surplus production. From 1970-2002, this was the only NE Atlantic stock showing a rising trend in biomass (1.6% annually) despite increases in fishing period over the same period (1.8 annually)(ICES WKDRCS Report 2006).

Cod in Division VIIa (Irish Sea) - ICES advises no directed fisheries. Fisheries for this species have been closed since 2003 in response to declines in SSB (ICES Advice 2013).

Cod in Division VIb - Rockall - ICES considers this to be a data-limited stock.

Cod in Division VIa (West of Scotland) -  This stock is suffering from reduced reproductive capacity and the harvest of this stock is considered unsustainable; B_current is well below B_lim, and SSB had steadily declined from about 40t tonnes in  1981 to less than 3t tonnes in 2012. Management measures taken thus far have not recovered the stock and have not constrained catches (ICES Advice 2013).

Cod in Subdivision Vb2 (Faroe Bank) - Because of very low stock size, ICES advises that the fishery should be closed. Fishery reopening should not be reconsidered until both survey indices indicate a biomass at or above the period 1996 - 2002.

Cod in subdivision Vb₁ Faroe Plateau - B_current is slightly above B_lim,and has been hovering around B_lim since 2005. F_current>F_msy  ICES recommends a 69% reduction in present fishing mortality. The overall trend in SSB is one of increase to peak of roughly 120t tonnes in the mid 1970s, followed by a decline to the series low of 20t tonnes in 1991; The stock has fluctuated, and is currently near the series low=B_lim=20t tonnes (ICES Advice 2013).

 

 

Gadus morhua larvae and postlarvae feed on phytoplankton, while juveniles feed predominantly on small crustaceans. An upsurge of cod-like fishes in the North Sea from 1962 onwards has been attributed to a one-month delay in copepod production (Cushing 1984). Older juveniles and adults feed on fishes and benthic organisms such as polychaetes and echinoderms (Cohen et al. 1990) Cod is a top-predator in the ecosystem. There are varying degrees of migratory and sedentary behavior observed in this species. Based on populations studied in the North Atlantic, there is a proportion of G. morhua which did not migrate a significant distance from their release location (Robichaud and Rose 2004).

Gadus morhua aggregates to particular geographic localities annually to spawn annually (Brander 1975), many of which are well-known in the Northeastern Atlantic. In the North Atlantic, reproduction generally occurs once per year from December to June, with some temporal variation by sub-population. Reproduction in the western Atlantic occurs near the substrate, and occurs at temperatures near 0-1°C, however temperature varies, and in the North Sea reproduction occurs at higher temperatures. Reproduction is localized, by sub-population. Longevity is reported to be as high as 20 to 25 years. There are occasional reports of hermaphroditism, and average fecundity is 1 million eggs/female (Cohen 1990).

An analysis of 22 North Atlantic Cod stocks (Gadus morhua) identified 4 patterns of sexual maturation: maturation early in life and at small size, early in life at large size, late in life at small size, and late in life at large size. These patterns clustered geographically. Recruit production of northernmost stocks was lowest and variability highest, mid-latitude stocks exhibited highest productivity and least variability, while stocks at the southern distribution range also showed low productivity (Köster et al. 2013).

In general, Northeastern Atlantic stocks have higher growth rates, mature at younger ages, and have higher surplus production than  Northwestern Atlantic stocks inhabiting colder waters (Dutil and Brander 2003), as temperature ranges in the North western Atlantic are generally less extreme, and have less of an effect on growth and recruitment. In the Western Atlantic there are variations in age of first maturity. Estimates of at 50% maturity range from 2-8 years (Lilly et al. 2003, Olsen et al. 2005, Olsen et al. 2004). In the Western Atlantic, age at 50% maturity for females has decreased over time from 6 years in 1980s to 4.5 to 5 years in the mid-1990s, and age-specific body lengths declined by about 15-25 cm through the 1980s and early 1990s as maturation has shifted towards early ages and smaller body lengths (Olsen et al. 2005).

In the Northeastern Atlantic, there is great variability in the age of first maturity (from 2 to 7 years) and age at 50% maturity (from 3 to 7 years), and longevity may be as high as 20 years (ICES 2005).  Average generation length across the region is therefore variable, ranging from 2-7 years, and possibly increasing in the Arctic stock of this species. However, age of first maturity and longevity also appear to have decreased over time. For example, in the Baltic Sea in the 1930s, cod typically matured at 8-11 years, while now they typically mature at 6 (46% mature), and 8 (89% mature) years. In 1987, average age of reproducing adults was 15 years (HELCOM Fact sheet), however, ICES calculates current generation times for the Baltic Sea stocks at 2-5 years (ICES Advice 2013). In 2010, weighted average generation length for the Arctic, Norwegian coastal and North Sea stocks was 6.9 years (Norwegian Red List Assessment). In the Flemish Cap, age at 50% maturity varied from 5-7 during the 1980s, but declined to 4 during the 1990s (ICES 2005).

By far, the greatest threat to G. morhua is over-exploitation (Rose et al. 2000, Froese and Pauly 2003, Handegard et al.2003, Harvey et al. 2003, Sellers 2003, Cardinale and Svedäng 2004, Suuronen et al. 2007, Urbach and Cotton 2008).

Additionally, variability in climate has contributed to variability in recruitment, growth, and natural mortality. Cooling events during the last 3 decades of the 20th century contributed to the rapid decline of Northwest Atlantic stocks, and changes in life-history traits and in the biotic environment are contributing to an unexpectedly slow recovery (Lilly et al. 2008). The ability to “rebuild” cod stocks that have declined to very low levels may be limited, and turning off directed fishing pressure may be insufficient to promote recovery in stocks which have already declined to low levels (WKDRCS 2006). For example, the warming of the North Atlantic during the 1920s and 1930s led to a rapid increase in abundance of G. morhua off West Greenland and northward range expansions. Subsequent cooling events in West Greenland in the 1960s, as well as increases in fishing pressure led to substantial declines in stock biomass and collapse of the stock. Cod have been subjected to changes in climate and fishing intensity for centuries, however detailed information on declines and recoveries comes primarily from the last 30 to 40 years.

The Atlantic Cod has also lost spawning grounds in parts of its range (Baltic Sea) due to oxygen deficiency (ICES Advice 2012).

This is a highly commercial species. It is one of the most important commercial fish species. Thirty-five percent of the 2.23 million tonnes of demersal fishes landed in the NE Atlantic were cod. Norway and Iceland are the primary fishing fleets targeting cod in the NE Atlantic, however it is taken as a bycatch species in almost all demersal and some pelagic fisheries (Reiss et al. 2009). Gadus morhua is caught primarily with bottom otter trawls and pelagic trawls. It is also taken by gillnets, which have replaced handlines and cod traps in parts of its range. Other types of gear used include longlines, Danish Seines, purse seines, twin beam trawls, light trawls, shrimp trawls, and pound nets. Major fishing grounds are Boreo-arctic, mainly around Iceland, in the Barents Sea, off Newfoundland, and West Greenland, in the Norwegian Sea, Off Sptzbergen, and around Bear Island. It is marketed fresh, frozen, and chilled as fillets or whole, salted or sugar-salted, dried and salted, dried and unsalted, in brine, or smoked. It is processed into liver oil, and eggs are marketed as smoked or as frozen roes (FAO)

All stocks for this species are currently under management plans with annual total allowable catches, temporal and spatial closures, protected areas, and various gear restrictions and rebuilding plans. Reductions in exploitation rate led to the improvement of some cod stocks in the Eastern Atlantic, however it is notable that despite stringent management measures, some cod stocks in the eastern Atlantic remain in poor condition (Fernandes and Cook 2013)

Gadus morhua was assessed as Vulnerable (VUA2b + A2c) in the HELCOM 2013 assessment. This assessment resulted from the combined assessments of several sub-populations of the Baltic Sea Cod: Western Baltic Cod (NTA2b), Eastern Baltic Cod (VUA2b +A2c), and Kattegat Cod (CR A2b and A2c).