Atlantic Cod:

the Good, the Bad, and the Rebuilding

Part I

By Gretchen Thuesen


Atlantic cod have been emblematic of fisheries problems, with the 1992 collapse of the Northern cod stock in Canada setting the stage for the last 25 years of concern surrounding status of cod stocks. Mark Kurlansky’s book “Cod” sold over a million copies, increasing awareness and concern over cod fisheries. Further, the two U.S. cod stocks continue to be at very low abundance; an article in the Houston Press released September of 2011 stated “Atlantic cod has been fished nearly to extinction.” However, over the entire Atlantic Ocean, the abundance of cod is high and increasing (Figure 1).

Figure 1. Abundance (in metric tons) of Atlantic cod from 1970 – 2010.

The purpose of this feature is to clarify the myriad of different claims recently released regarding the current status of Atlantic cod to highlight that not all is doom and gloom, but rather a mixed story of good and bad. In other words, not all stocks are low, failing to recover, and doomed to perish. In fact, what we actually see are three broad categories of stocks: those that are doing poorly, those that are low but rebuilding, and those that are large and doing well. In researching this story, we analyzed abundance data collected by scientific institutions and interviewed a range of scientists who have been involved in cod stock assessment and management over the last 15-35 years. These experts include: Chris Zimmermann, Director of the Thünen Institute of Baltic Sea Fisheries, Germany, with 20 years of experience working on ICES stocks; Coby Needle, Head of the Sea Fisheries Programme at MSS Marine Laboratory in Aberdeen, Scotland and an active member of several ICES working groups for 20 years; Jake Rice, Chief Scientist Emeritus at the Department of Fisheries and Oceans, Canada (DFO) with 35 years of experience in cod stock assessment; Robin Cook, a Senior Research Fellow in the MASTS Population Modelling Group at the University of Strathclyde, Glasgow who has been involved in ICES fisheries science since 1982; and Steve Murawski, a Professor of Biological Oceanography at University of South Florida (USF) with 7 years of experience as a Chief Scientist at the U.S. National Marine Fisheries Service (NMFS).

The story of cod is complex; there are many different and unique stocks occupying distinct regions within the Atlantic basin that are subject to environmental factors and political influences that differ based on geographic location. “If you look at the whole picture, you see that there is no consistent whole picture…Every single stock develops differently” says Chris Zimmermann. “Stock dynamics are quite different from area to area, so a big picture is difficult to get a handle on because there isn’t one,” agrees Coby Needle. Further, “they all have very different management histories and scenarios in terms of their status” says Steve Murawski.

Status of Stocks

There are over two dozen cod stocks that are defined as management units, 6 of which are addressed in this feature: 2 on the western side and 4 on the eastern side of the Atlantic basin (see Figure 2). The two U.S. stocks are Georges Bank and Gulf of Maine, and the four European stocks occupy the shelves of Iceland, the Barents Sea, the North Sea, the Celtic Sea, and the Baltic Sea.

Figure 2. Map showing location of 6 different cod stocks addressed in this feature. The darker blue region represents Atlantic cod distribution, and the 6 circles represent stocks being examined in this feature. Red circles represent stocks that are doing poorly (Celtic Sea, Gulf of Maine, Georges Bank), yellow circles represent stocks that are low but recovering (North Sea), and green circles represent stocks that are doing well (Barents Sea, shelves of Iceland).

This feature focuses on the general trends among most of these stocks to demonstrate that rather than all stocks doing poorly, what we actually see are 3 broad categories of stocks: those that are (1) doing poorly, (2) low but rebuilding, and (3) doing well.

Doing Poorly – Celtic Sea, Gulf of Maine, Georges Bank

Celtic Sea

“Fishing mortality has been declining in recent years and is uncertain, but remains above Flim (Editor’s note: Flim is a fraction harvested that causes concern about sustainability). The spawning-stock biomass has declined tenfold since the late 1980s and has had reduced reproductive capacity since the mid-1990s. The spawning-stock biomass increased from 2010, although it still remains well below Blim (Editor’s note: Blim is the biomass level that is of concern). Recruitment has been low since the mid-1990s.” (ICES 2014) (Figure 3a).

In January of this year SeaFish reported “the status of the Celtic Sea cod stock is poor…biomass and fishing mortality is outside precautionary limits and [the stock] is at risk of impaired recruitment.” (SeaFish 2016). In the Celtic Sea, “cod are doing quite badly according to the assessment, at least in comparison with the years before 2000” agrees Coby Needle.

Figure 3. Historical (top) Spawning Stock Biomass (SSB) and total catch (bottom) for Celtic Sea Cod. All data from ICES reports, 2016.

Gulf of Maine

“The Gulf of Maine Atlantic cod stock is overfished and overfishing is occurring. (Figure 4). 2013 spawning biomass levels are the lowest ever estimated and are at 4% or 3% of the SSBMSY proxy. The 2013 fully selected fishing mortality is estimated to be greater than 1.2, which is more than 6 times greater than the FMSY proxy. Fishing mortality is near all-time highs despite the fact that fishery catches are at the lowest levels in the time series. The Gulf of Maine cod stock is in poor condition.” (NEFSC 2014).

Last year (2015) NPR interviewed Andrew Pershing, an oceanographer at the Gulf of Maine Research Institute, about the struggling cod population in the Gulf of Maine.  Pershing explained, “[fishery managers] thought that [cod populations] should be rebuilding, but they were actually declining.” (2015). “In really warm years, every female cod produces fewer babies than we would expect, and we also see that the young fish are less likely to survive and become adults, said Pershing.” (NPR 2015).

Figure 4. Historical (top) Spawning Stock Biomass (SSB) and total catch (bottom) for Gulf of Maine Cod. All data from Northeast Fisheries Science Center reports and RAM Legacy Database.

Georges Bank

“Based on this updated assessment, the Georges Bank Atlantic Cod (Gadus morhua) stock is overfished and overfishing is occurring. (Figure 5). Spawning stock biomass in 2014 was estimated to be 6,180mt which is 3% of the biomass target for this stock. Adjusting for retrospective bias, SSB in 2014 is estimated to be 1,804mt which is 1% of the biomass target for this stock. The 2014 fully selected fishing mortality was estimated to be 0.463 which is 274% of the overfishing threshold proxy. Adjusting for retrospective bias, F in 2014 is estimated to be 1.68 which is 994% of the overfishing threshold for this stock. (Northeast Fisheries Science Center 2015).

Last year The Associated Press reported Georges Bank cod boats, “caught about 3.3 pounds of cod each time the net went in and out of the water last spring, compared with more than three times that amount two years earlier.”

Figure 5. Historical (a) Spawning Stock Biomass (SSB) and (b) total catch for Georges Bank Cod. All data from Northeast Fisheries Science Center reports and RAM Legacy Database.

Low But Rebuilding – North Sea

“Fishing mortality (F) declined from 2000 but is estimated to be above FMSY. Spawning-stock biomass (SSB) has increased from the historical low in 2006 to a level above Blim and remains below MSY Btrigger. Recruitment since 1998 has been poor” (ICES 2015) (see Figure 6).

Last year Arthur Nelsen of The Guardian reported on the Marine Conservation Society’s (MCS) shift of North Sea Cod off of the “avoid list”. (2015). But he explained that while this news was encouraging, “don’t rush to the chippie just yet.” North Sea Cod was and still is recovering, but slowly. Robin Cook, Chris Zimmermann, Steve Murawski, and Coby Needle all agree that North Sea cod are recovering, albeit slowly. “The North Sea stock…has had a long history of ups and downs” says Steve Murawski. The stock declined substantially in the past 20 years or so, but now the stock seems to be “improving year by year” says Coby Needle, although it is not yet fully recovered. Further, status differs between southern and northern populations, with southern populations in the North Sea having recovered less than their northern equivalents. “There’s an indication that this difference might be because the center of density of populations is now further north than south, and perhaps a response to climate” says Robin Cook.

Figure 6. Historical (top) Spawning Stock Biomass (SSB) and total catch (bottom) for North Sea Cod. All data from ICES reports, 2016.

Doing well – Barents Sea, Iceland

Barents Sea

The Barents Sea cod stock is at one of its highest levels in 70 years and has recovered considerably since 2000 but did show a recent decline (Figure 7). “The spawning-stock biomass (SSB) has been above MSY Btrigger since 2002. The total stock biomass (TSB) reached a peak in 2013 and is still close to this. Fishing mortality (F) was reduced from well above Flim in 1997 to below FMSY in 2007. Since 2012 fishing mortality shows an increasing trend and is above FMSY in 2014. Surveys indicate that year classes 2010–2014 are slightly above the long-term average.” (ICES 2015).

This success compares favorably to similar cod stock across the Atlantic. John Waldman, professor of Biology at Queens College explained in 2014 that, “on both sides of the Atlantic, it’s the same species with the same habitat facing the same societal reliance on this staple food source and economic engine. And yet [the Barents Sea] fishery now yields a sustainable annual catch of one million tons, while the [Western Atlantic cod fisheries] have failed or are failing.” (Waldman 2014).

Robin Cook, Steve Murawski, and Coby Needle all agree that the Barents Sea stock has done well and is now increasing quite strongly. “This stock…has, I think, actually improved productivity…and seems to be doing well” says Steve Murawski. “A couple of years ago they’d never seen so many cod” says Coby Needle.

Figure 7. Historical (top) Spawning Stock Biomass (SSB) and total catch (bottom) for Barents Sea Cod. All data from ICES reports, 2016.


Icelandic cod has been recovering steadily in recent years and management has been sound. In 2013 CBC reported, “the latest scientific data show[ed] spawning cod [were] at their highest levels in almost 50 years.” (CBC News 2013). Catch has been declining since the lowest biomass was reported in 1995. (Figure 8).

“The spawning-stock biomass (SSB) of Icelandic cod is increasing and is higher than has been observed over the last four decades. Fishing mortality (F) has declined significantly in the last decade and is presently at a historical low. Year classes are estimated to have been relatively stable since 1988, but with the mean around the lower values observed in the period 1955 to 1985.” (ICES 2015). Both Robin Cook and Chris Zimmermann agree that the Icelandic stock has improved, and “is developing favorably.”

Figure 8. Historical (top) Spawning Stock Biomass (SSB) and total catch (bottom) for Icelandic Cod. All data from ICES reports, 2016.
Editor’s note: A few days after publishing this, Fred Serchuk contacted us with the following note: I think it might be useful for the discussion on Atlantic cod to include the table of world-wide catches of cod, by stock, that I prepared (see below).  This will provide some insight into the magnitude of catches among the various stocks.

Listen to all the interviews featured in this story below (alphabetical order)

Robin Cook

Robin Cook is a Senior Research Fellow in the MASTS Population Modelling Group at the University of Strathclyde, Glasgow. Prior to that, he served as Chief Executive and Director in Fisheries Research Services for 7 years, the Head of Science Marine Scotland for 2 years, and was the Executive Secretary of the European Fisheries and Aquaculture Organisation (EFARO) from 2011-2015. Additionally, he currently serves as an external scientific advisor to the EU-MareFrame project.

Robin has been involved in International Council for the Exploration of the Sea (ICES) fisheries science since 1982, and he was the UK delegate on the ICES Council from 2002-2010 and Chairman of Consultative Committee (ICES Chief Scientist) from 1997-2000.

Steve Murawski

Steve Murawski is a Professor and Peter Betzer Endowed Chair of Biological Oceanography at University of South Florida (USF), College of Marine Science. His areas of expertise include population dynamics of exploited marine species, impacts of fishing and other anthropogenic stresses on marine ecosystems, and ecosystem modeling and analysis. Prior to that, Steve spent 7 years at NMFS in Silver Spring, Maryland, first as the Director of the Office of Science & Technology and then as the Director of Scientific Programs and Chief Science Advisor.

Further, Steve received the Presidential Rank Award for Meritorious Service, conferred by President Barak Obama, in 2009, and the Dwight A. Webster Memorial Award for “meritorious/prestigious service to the profession and fisheries” in 2011.

Coby Needle

Coby Needle is Head of the Sea Fisheries Programme at MSS Marine Laboratory in Aberdeen, Scotland. He has worked there for 21 years on a wide range of fish stock and fishery-related research areas, including fish condition and recruitment, survey-based assessment methods, and management strategy evaluations.

Coby is also an active member of several ICES working groups, particularly the WG on the Assessment of Demersal Stocks in the North Sea and Skagerrak (which he chaired from 2004-2006), and he is an alternate UK member of ACOM (the advisory committee of ICES).  He is also an active review member of the American Centre for Independent Experts, and he provides advice on fish stocks and fisheries to the Scottish and UK governments, as well as the European Commission.

Jake Rice

Jake Rice is Chief Scientist-Emeritus at the Department of Fisheries and Oceans, Canada (DFO), and has been deeply involved in Atlantic cod assessments for the past 35 years. He was Head of the Groundfish Division in the Newfoundland Region at DFO during the early days of the cod collapse in the 1980s. Additionally, he was the first Director of Peer Review and Scientific Advice at DFO – a position that required staying abreast of Northern Cod science, and one he held for 11 years., prior to being appointed Chief Scientist in the mid 2000’s.

Jake also served as the Canadian member of ICES advisory committee on fisheries management for 10 years, and received the ICES Outstanding Achievement Award in 2009.

Chris Zimmermann

Christopher Zimmermann is the Director of the Thünen Institute of Baltic Sea Fisheries. He is a member of many International Council for the Exploration of the Sea (ICES) expert groups, having worked on ICES stocks for the last 20 years. Chris has chaired some of these groups, and is currently the German member of the ICES Advisory Committee and ICES delegate. Additionally, Chris has been a member of various Scientific, Technical and Economic Committee for Fisheries (STECF) expert groups, a member of the EU Marine Observation and Data Expert Group, and is an ex officio member of the MSC Board of Trustees (as chair of their Technical Advisory Board). He has served as a scientific advisor to policy makers (regional, federal and EU administrations and parliaments), retailers and industry, and environmental NGOs.