Towards sustainable fisheries of the Öresund cod (Gadus morhua) through sub-stock-specific assessment and management recommendations

Abstract Lindegren, M., Waldo, S., Nilsson, P. A., Svedäng, H., and Persson, A. 2013. Towards sustainable fisheries of the Öresund cod (Gadus morhua) through sub-stock-specific assessment and management recommendations. – ICES Journal of Marine Science, 70: 1140–1150. Fisheries management traditionally relies on stock assessments assuming discrete populations within large administrational areas. However, failing to account for sub-stock structuring may result in overestimation of the stocks' true harvest potential and unsustainable exploitation of small stock elements. Atlantic cod (Gadus morhua) frequently occurs in spatially segregated populations, some of which exhibit fine-scaled stock structuring within current management boundaries. Here we use the locally spawning cod stock in the Sound (“Öresund”) as a case study, and perform a sub-stock-specific assessment to evaluate biological and economic effects of managing the Sound cod as a separate stock. Our results indicate that reducing exploitation pressure, particularly through technical regulations i.e. increasing gill-net mesh sizes, would not only enhance the stock age distribution, but yield long-term net benefits to the local gill-net fishery. Furthermore, our study emphasizes the need for developing sub-stock-specific management recommendations in order to ensure the maintenance of fisheries resources in general, and the persistence of sub-stock structuring in particular.

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Intergenerational valuation of fisheries resources can justify long-term conservation: a case study in Atlantic cod (Gadus morhua)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f05-010 ◽

2005 ◽

Vol 62 (5) ◽

pp. 1104-1110 ◽

Cited By ~ 12

Author(s):

C H Ainsworth ◽

U R Sumaila

Keyword(s):

Discount Rate ◽

Gadus Morhua ◽

Atlantic Cod ◽

Ecosystem Model ◽

Conventional Model ◽

Fisheries Resources ◽

Optimal Harvest ◽

Harvest Policies

Where the conventional model of discounting advocates aggressive harvest policies, intergenerational discounting could have been used to render the historic gross overfishing of Atlantic cod (Gadus morhua) economically unappealing compared with a more conservative long-term strategy. Under these discounting approaches, we compare the historic harvest trend from 1985 (and projected postcollapse earnings) with theoretical optimal harvest profiles determined by an ecosystem model. The optimal scenarios generate less initial harvest than the historic profile but maintain the resource and provide greater yields over the long term. At a discount rate equal to market interest, we demonstrate that it was more economic under conventional valuation to harvest the cod stock to collapse than it would have been to sustain the population. However, under intergenerational valuation, the sustainable optimal scenarios outperform the actual harvest profile. Application of conventional discounting by fishing consortiums may be partly to blame for depletion, yet management fell short of even that ideal.

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Cod and climate: a systems approach for sustainable fisheries management of Atlantic cod (Gadus morhua) in coastal Danish waters

Journal of Coastal Conservation ◽

10.1007/s11852-019-00711-0 ◽

2019 ◽

Vol 23 (5) ◽

pp. 943-958 ◽

Cited By ~ 2

Author(s):

Grete E. Dinesen ◽

Stefan Neuenfeldt ◽

Alexandros Kokkalis ◽

Andreas Lehmann ◽

Josefine Egekvist ◽

...

Keyword(s):

Fisheries Management ◽

Gadus Morhua ◽

Systems Approach ◽

Atlantic Cod ◽

Sustainable Fisheries

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Re-evaluating Atlantic cod mortality including lobster bycatch: where could we be today?

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2019-0313 ◽

2020 ◽

Vol 77 (6) ◽

pp. 1049-1058 ◽

Cited By ~ 1

Author(s):

Robert Boenish ◽

Yong Chen

Keyword(s):

Gadus Morhua ◽

Gulf Of Maine ◽

Atlantic Cod ◽

Homarus Americanus ◽

Small Scale ◽

Stock Biomass ◽

Stock Assessments ◽

Spawning Stock ◽

Assessment Bias ◽

Related Mortality

Full accounting of fisheries mortality is one of the most tractable ways to improve stock assessments. However, it can be challenging to obtain in cases when missing catch comes from small-scale nontarget fisheries unrequired to report incidental catch. Atlantic cod (Gadus morhua) in the Gulf of Maine (GoM), USA, once served as a regionally important fishery, but has been serially depleted to <5% of historic spawning stock biomass. Recent management efforts to rebuild GoM cod have largely failed. We test the hypothesis that unaccounted bycatch of Atlantic cod in the Maine American lobster (Homarus americanus) fishery is a substantial missing piece in the GoM Atlantic cod assessment. We integrated multiple scenarios of hind-casted discards into the two accepted regional cod assessment models from 1982 to 2016. Incorporation of discards improved the assessment bias for both models (10%–15%), increased estimates of spawning stock biomass (4%), and decreased estimates of fishing mortality (9%). A novel evaluation of longitudinal model bias suggests that alternative modelling approaches or specifications may be warranted. We highlight the importance of accounting for all fishery-related mortality and the need for methods to deliver more comprehensive estimates from both target and nontarget fisheries.

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Fisheries assessment: what can be learned from interviewing resource users?

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f99-115 ◽

1999 ◽

Vol 56 (10) ◽

pp. 1949-1963 ◽

Cited By ~ 150

Author(s):

Barbara Neis ◽

David C Schneider ◽

Lawrence Felt ◽

Richard L Haedrich ◽

Johanne Fischer ◽

...

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Local Information ◽

Detailed Knowledge ◽

Large Reservoir ◽

Seasonal Movement ◽

Cyclopterus Lumpus ◽

Spawning Areas ◽

Decadal Scale ◽

Stock Assessments

Fishers have detailed knowledge of their resources, their environment, and their fishing practices that is rarely systematically collected. We conducted three types of interviews with coastal Newfoundland fishers to identify the range of information available, to see if it could be quantified, and to explore its potential for reconstructing trends within fisheries. These fishers have many terms for Atlantic cod (Gadus morhua), each associated with characteristic patterns of seasonal movement and availability to gear and indicating the location of several coastal spawning areas. They described a variety of changes in fishing practice. Of the four changes that could be quantified, all contributed to decadal-scale increases in catch efficiency prior to 1992, while change in catch per unit of effort for cod was consistently negative at decadal scales. For these fishers' lumpfish (Cyclopterus lumpus) roe fishery, catch per unit of effort was consistently negative in the 1990s. We describe ways to access the large reservoir of information held by fishers, the use of several cross-checks to identify consistent patterns, and the use of trends and patterns to broaden the basis for interpreting quantitative surveys used in fisheries assessment. Local information from resource users can be assembled in forms usable in quantitative stock assessments.

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Consideration of the Stable Age Distribution Assumption in "Analytical" Yield Models

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f83-016 ◽

1983 ◽

Vol 40 (1) ◽

pp. 95-101 ◽

Cited By ~ 3

Author(s):

M. Sinclair ◽

R. O'Boyle ◽

T. D. Iles

Keyword(s):

Analytical Model ◽

Growth Rates ◽

Gadus Morhua ◽

Atlantic Cod ◽

Age Distribution ◽

Clupea Harengus ◽

Melanogrammus Aeglefinus ◽

Yield Model ◽

Stable Age Distribution ◽

Recruitment Variability

The implications on the "analytical" yield model of deviations from the stable age distribution were investigated for stocks of five species with a range of life history characteristics, these being Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), pollock (Pollachius virens), Atlantic herring (Clupea harengus harengus), and Atlantic mackerel (Scomber scrombus). Recruitment variability for the stocks considered ranged from 21% for pollock to 104% for haddock. The comparison of the growth rates at age for the five species showed the expected continuum in relative growth rates from cod to mackerel. With the population in a stable age distribution without fishing there is also a continuum from cod to mackerel in the manner in which age-specific production decreases through the life span. It is thus to be expected that deviations from the stable age distributions for mackerel would have a much greater impact on population production than would a similar deviation for cod. Also, species whose growth rates decrease more rapidly with age tend to have a higher recruitment variability. To demonstrate the implications of deviations from the stable age distribution on the accuracy of model output, MSY yields (that would have been generated given historical estimates of population numbers-at-age) were compared to estimates of annual population production. Cod and pollock production deviate relatively little from the "analytical" model predictions. In contrast, annual production for haddock, herring, and mackerel deviate markedly from MSY yields as the age composition deviates in each direction from the stable age distribution. The analysis suggests that for some species the "analytical" model may contribute to growth overfishing.Key words: "analytical" yield models, stable age distribution, growth overfishing

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Effects of temperature on life history set the sensitivity to fishing in Atlantic cod Gadus morhua

Marine Ecology Progress Series ◽

10.3354/meps10943 ◽

2014 ◽

Vol 514 ◽

pp. 217-229 ◽

Cited By ~ 11

Author(s):

HY Wang ◽

LW Botsford ◽

JW White ◽

MJ Fogarty ◽

F Juanes ◽

...

Keyword(s):

Life History ◽

Gadus Morhua ◽

Atlantic Cod ◽

Effects Of Temperature

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Responses of Atlantic cod Gadus morhua head kidney leukocytes to phytase produced by gastrointestinal-derived bacteria

Fish Physiology and Biochemistry ◽

10.1007/s10695-009-9364-0 ◽

2009 ◽

Vol 36 (4) ◽

pp. 883-891 ◽

Cited By ~ 14

Author(s):

Carlo C. Lazado ◽

Christopher Marlowe A. Caipang ◽

Sanchala Gallage ◽

Monica F. Brinchmann ◽

Viswanath Kiron

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Head Kidney

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Some recent data on sperm morphology and motility kinetics in Atlantic cod (Gadus morhua L.)

Fish Physiology and Biochemistry ◽

10.1007/s10695-020-00915-4 ◽

2021 ◽

Author(s):

Sayyed Mohammad Hadi Alavi ◽

Azadeh Hatef ◽

Ian A.E. Butts ◽

Olga Bondarenko ◽

Jacky Cosson ◽

...

Keyword(s):

Gadus Morhua ◽

Sperm Morphology ◽

Atlantic Cod

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Natural mortality from poor condition in Atlantic cod (Gadus morhua)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f00-023 ◽

2000 ◽

Vol 57 (4) ◽

pp. 826-836 ◽

Cited By ~ 96

Author(s):

Jean-Denis Dutil ◽

Yvan Lambert

Keyword(s):

Gadus Morhua ◽

Atlantic Cod ◽

Negative Impact ◽

Fish Muscle ◽

Early Summer ◽

Wild Fish ◽

Natural Mortality ◽

Muscle Lactate ◽

Lactate Dehydrogenase Activity ◽

Poor Condition

The extent of energy depletion was assessed in Atlantic cod (Gadus morhua) in spring and early summer (1993-1995) to assess relationships between poor condition and natural mortality. Several indices of condition were compared in wild fish in the northern Gulf of St. Lawrence and in fish exposed to a prolonged period of starvation in laboratory experiments. Discriminant analyses classified only a small fraction of the wild fish as similar to cod that did not survive and a much larger fraction as similar to cod that survived starvation. This percentage increased from April to May and peaked in June 1993 and 1994. Condition factor and muscle somatic index allowed a clear distinction between live and dead fish. Muscle lactate dehydrogenase activity suggested that cod had experienced a period of negative growth early in 1993, 1994, and 1995. Fish classified as similar to starved individuals were characterized by a higher gonad to liver mass ratio than others. Reproduction may have a negative impact on survival not only in spring but also later into summer, as some individuals were found not to have recovered by late summer. This study shows that natural mortality from poor condition contributed to lower production in the early 1990s.

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