Papers by Henrik Gislason
ICES Journal of Marine Science, 2014
Forage fish (FF) have a unique position within marine foodwebs and the development of sustainable... more Forage fish (FF) have a unique position within marine foodwebs and the development of sustainable harvest strategies for FF will be a critical step in advancing and implementing the broader, ecosystem-based management of marine systems. In all, 70 scientists from 16 nations gathered for a symposium on 12-14 November 2012 that was designed to address three key questions regarding the effective management of FF and their ecosystems: (i) how do environmental factors and predator -prey interactions drive the productivity and distribution of FF stocks across ecosystems worldwide, (ii) what are the economic and ecological costs and benefits of different FF management strategies, and (iii) do commonalities exist across ecosystems in terms of the effective management of FF exploitation?
PLoS ONE
Atlantic mackerel (Scomber scombrus) occurs on both sides of the north Atlantic and has tradition... more Atlantic mackerel (Scomber scombrus) occurs on both sides of the north Atlantic and has traditionally been grouped into 5 spawning components, some of which were thought to be isolated natal homing stocks. Previous studies have provided no evidence for cross Atlantic migration and no or weak support for isolated spawning components within either side of the North Atlantic. We question the de-facto accepted hypothesis of isolation between spawning components on the basis of spawning and age distribution data. The spawning intensities, proxied by larval abundances, are negatively correlated between the North Sea and Celtic Sea, which indicates that the two spawning components may be connected by straying individuals. This finding is based on unique larvae samples collected before the collapse of North Sea component, thus showing that the exchange is not a recent phenomenon due to the collapse. The analyses of old as well as more recent age distributions show that strong year classes s...
Continental Shelf Research
Climate change accentuates the need for knowing how temperature impacts the life history and prod... more Climate change accentuates the need for knowing how temperature impacts the life history and productivity of economically and ecologically important species of fish. We examine the influence of temperature on the timing of the spawning and migrations of North Sea Mackerel using data from larvae CPR surveys, egg surveys and commercial landings from Danish coastal fisheries in the North Sea, Skagerrak, Kattegat and inner Danish waters. The three independent sources of data all show that there is a significant relationship between the timing of spawning and sea surface temperature. Large mackerel are shown to arrive at the feeding areas before and leave later than small mackerel and the sequential appearance of mackerel in each of the feeding areas studied supports the anecdotal evidence for an eastward post-spawning migration. Occasional commercial catches taken in winter in the Sound N, Kattegat and Skagerrak together with catches in the first quarter IBTS survey furthermore indicate...
PLoS ONE, 2013
Atlantic mackerel (Scomber scombrus) occurs on both sides of the north Atlantic and has tradition... more Atlantic mackerel (Scomber scombrus) occurs on both sides of the north Atlantic and has traditionally been grouped into 5 spawning components, some of which were thought to be isolated natal homing stocks. Previous studies have provided no evidence for cross Atlantic migration and no or weak support for isolated spawning components within either side of the North Atlantic. We question the de-facto accepted hypothesis of isolation between spawning components on the basis of spawning and age distribution data. The spawning intensities, proxied by larval abundances, are negatively correlated between the North Sea and Celtic Sea, which indicates that the two spawning components may be connected by straying individuals. This finding is based on unique larvae samples collected before the collapse of North Sea component, thus showing that the exchange is not a recent phenomenon due to the collapse. The analyses of old as well as more recent age distributions show that strong year classes spread into other areas where they spawn as adults (''twinning''). Our findings are in accordance with the lack of solid evidence for stock separation from previous analyses of tagging data, genetics, ectoparasite infections, otolith shapes, and blood phenotypes. Because no method has been able to identify the origin of spawning mackerel unequivocally from any of the traditional spawning components, and in the light of our results, we conclude that straying outweighs spatial segregation. We propose a new model where the population structure of mackerel is described as a dynamic cline, rather than as connected contingents. Temporal changes in hydrography and mackerel behavior may affect the steepness of the cline at various locations. The new interpretation of the population structure of Atlantic mackerel has important implications for research, assessment and management. Citation: Jansen T, Gislason H (2013) Population Structure of Atlantic Mackerel (Scomber scombrus). PLoS ONE 8(5): e64744.
Journal of Experimental Marine Biology and Ecology, 2005
The functional response of whiting (Merlangius merlangus L.) to clupeid and gadoid prey was deter... more The functional response of whiting (Merlangius merlangus L.) to clupeid and gadoid prey was determined from estimates of food intake and prey density at five locations in the North Sea. The intake of most prey types was well described by a type II (decelerating) response, although in some cases a type III (sigmoid) response provided a slightly better fit. Though
Journal of Applied Statistics, 2000
... To cite this article: Trine Kvist, Henrik Gislason & Poul Thyregod (2000): Using continua... more ... To cite this article: Trine Kvist, Henrik Gislason & Poul Thyregod (2000): Using continuation-ratio logits to analyze the variation of the ... Any substantial or systematic reproduction, re-distribution, re-selling, loan, sub-licensing, systematic supply or distribution in any form to anyone ...
ICES Journal of Marine Science, 2001
... The logits were modelled by a linear model including both fixed and random effects: Lj=bj j+Z... more ... The logits were modelled by a linear model including both fixed and random effects: Lj=bj j+Zjuj where j=0, . . ., 3, bj denotes the explanatory variables associated with the fixed parameters j, and Zj the explanatory variables associated with the random par-ameters uj. ...
ICES Journal of Marine Science, 1999
. Single and multispecies reference points for Baltic fish stocks. -ICES Journal of Marine Scienc... more . Single and multispecies reference points for Baltic fish stocks. -ICES Journal of Marine Science, 56: 571-583.
Continental Shelf Research, 2011
Climate change accentuates the need for knowing how temperature impacts the life history and prod... more Climate change accentuates the need for knowing how temperature impacts the life history and productivity of economically and ecologically important species of fish. We examine the influence of temperature on the timing of the spawning and migrations of North Sea Mackerel using data from larvae CPR surveys, egg surveys and commercial landings from Danish coastal fisheries in the North Sea, Skagerrak, Kattegat and inner Danish waters. The three independent sources of data all show that there is a significant relationship between the timing of spawning and sea surface temperature. Large mackerel are shown to arrive at the feeding areas before and leave later than small mackerel and the sequential appearance of mackerel in each of the feeding areas studied supports the anecdotal evidence for an eastward postspawning migration. Occasional commercial catches taken in winter in the Sound N, Kattegat and Skagerrak together with catches in the first quarter IBTS survey furthermore indicate some overwintering here. Significant relationships between temperature and North Sea mackerel spawning and migration have not been documented before. The results have implications for mackerel resource management and monitoring. An increase in temperature is likely to affect the timing and magnitude of the growth, recruitment and migration of North Sea mackerel with subsequent impacts on its sustainable exploitation.
Canadian Journal of Fisheries and Aquatic Sciences, 1993
1991) are multispecies extensions to the single-species VPA (Gulland 1965) and forecast model (Th... more 1991) are multispecies extensions to the single-species VPA (Gulland 1965) and forecast model (Thompson and Bell 1934) in which biological interaction due to predation is taken into account. The MSVPAutilizes catch-at-age and food composition data to estimate fishing mortality, predation mortality, and stock sizes. The MSFOR is the predictive counterpart of the MSVPA and includes both technical and biological interaction. Given estimates of future recmitment a d fishing mortality the MSFOR can be used to predict long-tem yield and biomass.
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Papers by Henrik Gislason