Temporal and spatial patterns of reproductive indices of European hake ( Merluccius merluccius ) in the northern North Sea and Norwegian coastal areas

Werner, Karl Michael; Staby, Arved; Geffen, Audrey J.

doi:10.1016/j.fishres.2016.06.008

Cited by 9 publications

(9 citation statements)

References 22 publications

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“…For example, 94% of SSB was allocated to the Celtic Sea and around 6% to the Bay of Also, the estimated spatial pattern of recruitment allocates most recruitment (67%) to the Bay of Biscay, less (21%) to the Celtic Sea and least (12%) to the northern area over the time series (Figure 7). This result is rather expected on the basis of the literature and surveys with known nursery areas mostly located in the Bay of Biscay, then the Celtic Sea (Casey and Pereiro, 1995) and lastly the northern area (Guichet, 1996;Quéro and Vayne, 1997;Werner et al, 2016); the spatial distribution of recruits observed by the EVHOE survey showed higher recruitment in the Bay of Biscay than in the Celtic Sea (ICES, 2016).…”

Section: Perception Of the Fishery And Stock Dynamics Supported By Thsupporting

confidence: 52%

Towards a spatial integrated stock assessment model for European hake northern stock

2018

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European hake (Merluccius merluccius) is a key species in the management of several mixed fisheries in the northeast Atlantic where regional spatial management plans are being set up. The wide spatial distribution of hake and the lack of knowledge of some processes involved in its spatial dynamics could hamper the assessment and management of hake. To help understand the processes, we implemented a spatial version of the Stock Synthesis stock assessment model for northern hake, including available data on this stock and the associated fisheries. For the 1978-2012 time series, the model distinguished the Bay of Biscay, the Celtic Sea and a northern area aggregating the West of Scotland and the North Sea. The model considered an agestructured population for each age class and area, a seasonal migration, global recruitment allocated to areas and fishing fleets for each area. Parameters for stock and exploitation spatio-temporal dynamics were estimated by likelihood maximization for each quarter and area. The comparison of spatial and non spatial models goodness of fit showed they were close, although the fit to abundance indices slightly improved with the spatial model. Fishing mortalities, spawning stock biomasses and recruitments were slightly different from the current assessment model estimates, essentially at the beginning and the end of the time series. On average over the time series, fishing mortality estimates relative to the abundance were higher in the Bay of Biscay than elsewhere, spawning stock biomass estimates were higher in the Celtic Sea than elsewhere, and recruitment occurred mainly in the Bay of Biscay. Finally, the final spatial model estimated a strong movement from the northern area to the Celtic Sea. The final spatial model is a step towards a spatial assessment and management of the stock.

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Section: Perception Of the Fishery And Stock Dynamics Supported By Thsupporting

confidence: 52%

Towards a spatial integrated stock assessment model for European hake northern stock

2018

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“…Despite a series of accomplishments, management agreements might be seriously put to the test, when stock size and/or stock distribution are undergoing rapid change (Figures 3 and 5), as witnessed with IUU fishing in the Loophole for Barents Sea cod (Table S2: JNRFC; Kjesbu et al., 2014). The Northern hake stock has also significantly enlarged in size and spatially (Werner et al., 2016), although not into international seas but seeing the creation of a new independent coastal state, the UK (Shepherd & Horwood, 2019). In the case of Northeast Atlantic mackerel, the major north‐westward extension was foreshadowed in the 1990s (Astthorsson et al., 2012) but materialized with the recent peak in stock abundance (dos Santos Schmidt et al., 2020; Nøttestad et al., 2016) (Figure 5).…”

Section: Discussionmentioning

confidence: 99%

“…Traditionally, the main habitat of European hake has been located south of the North Sea, although this species is generally widely distributed—from the Mediterranean, along the Iberian and French coast, west of the British Isles and Irish Sea to the North Sea, and further northwards to the Norwegian coast around 64° N and westward towards Iceland (Heessen & Murua, 2015; Werner, Staby, & Geffen, 2016). It is uncertain whether the European hake is divided into sub/metapopulations, but within ICES, it is managed as one southern and one northern stock unit, divided at the Cap Breton Canyon in the Bay of Biscay (ICES, 2012).…”

Section: Case‐studies Illustrating How Climate May Impact Stock Distributionmentioning

confidence: 99%

“…There are indications that AMO might be an explanatory forcing of this displacement. Subsequent to the recent substantial increase in SSB, major spawning areas were established after 2014 along the western slope of the Norwegian Trench in the North Sea (Sundby et al, 2017; Werner et al., 2016). Thus, with ongoing climate change, there are indications that Northern hake is taking over much of what used to be the central role of North Sea cod in the northern North Sea, although there is no evidence that hake is actually outcompeting the cod.…”

Section: Case‐studies Illustrating How Climate May Impact Stock Distributionmentioning

confidence: 99%

“…Lastly, since hake was practically absent from the North Sea until rather recently, it is often considered an “invasive species.” The catch history indicates that the stock should be considered an endemic species to the North Sea. The northern limit for egg release is around 64° N, reflecting lesser spawning ground habitat exists along the Norwegian coast (Werner et al., 2016). Northward expansion of spawning areas is uncertain given the species' year‐round spawning activity (Serrat et al., 2019), because spring‐spawning behaviour is a necessary adaptation at latitudes higher than 66–67 N due to the restricted timing of blooming of suitable prey for the fish larvae (Sundby, Drinkwater, & Kjesbu, 2016).…”

Section: Case‐studies Illustrating How Climate May Impact Stock Distributionmentioning

confidence: 99%

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Management of transboundary and straddling fish stocks in the Northeast Atlantic in view of climate‐induced shifts in spatial distribution

2020

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The introduction of 200 n.m. exclusive economic zones (EEZs) in the late 1970s required increased collaboration among neighbouring coastal states to manage transboundary and straddling fish stocks. The established agreements ranged from bilateral to multilateral, including high‐seas components, as appropriate. However, the 1982 United Nations Convention on the Law of the Sea does not specify how quotas of stocks crossing EEZs should be allocated, nor was it written for topical scenarios, such as climate change with poleward distribution shifts that differ across species. The productive Northeast Atlantic is a hot spot for such shifts, implying that scientific knowledge about zonal distribution is crucial in quota negotiations. This diverges from earlier, although still valid, agreements that were predominately based on political decisions or historical distribution of catches. The bilateral allocations for Barents Sea and North Sea cod remain robust after 40 years, but the management situation for widely distributed stocks, as Northeast Atlantic mackerel and Norwegian spring‐spawning herring, appears challenging, with no recent overall agreements. Contrarily, quotas of Northern hake are, so far, unilaterally set by the EU despite the stock's expansion beyond EU waters into the northern North Sea. Negotiations following the introduction of EEZs were undertaken at the end of the last cooler Atlantic Multidecadal Oscillation (AMO) period, that is, with stock distributions generally in a southerly mode. Hence, today's lack of management consensus for several widely distributed fish stocks typically relates to more northerly distributions attributed to the global anthropogenic signal accelerating the spatial effect of the current warmer AMO.

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Ecological connectivity of the marine protected area network in the Baltic Sea, Kattegat and Skagerrak: Current knowledge and management needs

Berkström

Wennerström

Bergström

2021

Ambio

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Marine protected areas (MPAs) have become a key component of conservation and fisheries management to alleviate anthropogenic pressures. For MPA networks to efficiently promote persistence and recovery of populations, ecological connectivity, i.e. dispersal and movement of organisms and material across ecosystems, needs to be taken into account. To improve the ecological coherence of MPA networks, there is hence a need to evaluate the connectivity of species spreading through active migration and passive dispersal. We reviewed knowledge on ecological connectivity in the Baltic Sea, Kattegat and Skagerrak in the northeast Atlantic and present available information on species-specific dispersal and migration distances. Studies on genetic connectivity are summarised and discussed in relation to dispersal-based analyses. Threats to ecological connectivity, limiting dispersal of populations and lowering the resilience to environmental change, were examined. Additionally, a review of studies evaluating the ecological coherence of MPA networks in the Baltic Sea, Kattegat and Skagerrak was performed, and suggestions for future evaluations to meet management needs are presented.

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Temporal and spatial patterns of reproductive indices of European hake ( Merluccius merluccius ) in the northern North Sea and Norwegian coastal areas

Cited by 9 publications

References 22 publications

Towards a spatial integrated stock assessment model for European hake northern stock

Towards a spatial integrated stock assessment model for European hake northern stock

Management of transboundary and straddling fish stocks in the Northeast Atlantic in view of climate‐induced shifts in spatial distribution

Ecological connectivity of the marine protected area network in the Baltic Sea, Kattegat and Skagerrak: Current knowledge and management needs

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