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Range size changes within the North Sea fish assemblage

Fredricson, Jonatan (2015) BIOP35 20141
Degree Projects in Biology
Abstract
The North Sea stands out as one of the most rapidly warming regions of the globe and various types of geographic distribution responses have already been reported, from latitudinal changes to vertical changes. Using catch data from an international bottom trawling monitoring survey, this study investigated how the range size of the North Sea fish assemblage has changed during the last three decades, and in which way is climate change responsible for the range changes. The mean annual and third quarter SST has warmed significantly in the last 30 years. However, a higher proportion of range size changes have been observed during the first quarter and more were better correlated with SST than in quarter three. The proportion of species... (More)
The North Sea stands out as one of the most rapidly warming regions of the globe and various types of geographic distribution responses have already been reported, from latitudinal changes to vertical changes. Using catch data from an international bottom trawling monitoring survey, this study investigated how the range size of the North Sea fish assemblage has changed during the last three decades, and in which way is climate change responsible for the range changes. The mean annual and third quarter SST has warmed significantly in the last 30 years. However, a higher proportion of range size changes have been observed during the first quarter and more were better correlated with SST than in quarter three. The proportion of species expanding differed significantly depending on their biogeographic affinity and maximum length was found to significantly predict the rate of range size change of boreal species. The slight winter warming seems to have allowed a series of expansions among North Sea species, as well as the persistence of southern species increasing the species richness. Range contraction were also observed among larger northern species, specially among fisheries targeted one. The reported range size changes will have ecological consequences, potentially affecting the ecosystems productivity and should be taken into account when developing future conservation and fisheries strategies in the future. (Less)
Popular Abstract
Contractions and expansions in the North Sea fish assemblage

The global climate is warming up, resulting in changes in species distribution patterns. Due to the warming trend and because of the cooling pattern from the equator to the poles, ecologists expect species to move their ranges polewards to remain within their preferred temperatures. However, studies have found that a majority of species are not moving in the expected direction, while others are not moving at all, and even within shifting species, the leading edges of their expanding ranges tend to move at much higher rates compared to the backend of their ranges. Therefore, I decided to focus my work on the changes in the ranges sizes rather than the directionality.

I... (More)
Contractions and expansions in the North Sea fish assemblage

The global climate is warming up, resulting in changes in species distribution patterns. Due to the warming trend and because of the cooling pattern from the equator to the poles, ecologists expect species to move their ranges polewards to remain within their preferred temperatures. However, studies have found that a majority of species are not moving in the expected direction, while others are not moving at all, and even within shifting species, the leading edges of their expanding ranges tend to move at much higher rates compared to the backend of their ranges. Therefore, I decided to focus my work on the changes in the ranges sizes rather than the directionality.

I centered my work on the North Sea, where I modelled how the ranges of the species have been changing during the last 31 years for the first and third quarters of the year separately. I also tested to see if using temperature as a variable could improve the quality of the model for each species, in order to see if temperature was an important factor in the range size dynamics of each species. Lastly, I also tested if the proportion of expansion differed from contractions between different species traits, where I included geographic affinity, horizontal habitat and size of the fish.

The study found that a high number of expansions had been taking place and that these expansions were most commonly recorded during the winter months. Also, among the species expanding during winter, a high proportion was being strongly affected by sea surface temperatures. The results indicate that the increasing winter temperatures may have resulted in an increased survival of many species allowing them to flourish, as well as an increased availability of suitable winter habitat. The almost freezing winter temperature, which used to restrict the ranges of many species into shallower regions, may now be more suited for overwintering.

The proportion of expansions was shown to be higher among southern species, an expected result due to their preference for warmer waters, The results also suggest that coastal species were more prompt to expand was also found. Lastly, fish size was found to be important predicting expanding or contracting rates among northern species, and while large northern species seem to be contracting, some large southern fish are expanding. This indicates that a shift in the top trophic level of the North Sea may be taking place. The high number of expansion is also expected to result in range overlaps increased competition and high number of local extinctions in the future.

Advisor: Mark Payne (DTU) & Per Carlsson (LU)
Degree project 60 credits in 2014-2015
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Fredricson, Jonatan
supervisor
organization
course
BIOP35 20141
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
5276785
date added to LUP
2015-04-28 15:25:22
date last changed
2015-04-28 15:25:28
@misc{5276785,
  abstract     = {The North Sea stands out as one of the most rapidly warming regions of the globe and various types of geographic distribution responses have already been reported, from latitudinal changes to vertical changes. Using catch data from an international bottom trawling monitoring survey, this study investigated how the range size of the North Sea fish assemblage has changed during the last three decades, and in which way is climate change responsible for the range changes. The mean annual and third quarter SST has warmed significantly in the last 30 years. However, a higher proportion of range size changes have been observed during the first quarter and more were better correlated with SST than in quarter three. The proportion of species expanding differed significantly depending on their biogeographic affinity and maximum length was found to significantly predict the rate of range size change of boreal species. The slight winter warming seems to have allowed a series of expansions among North Sea species, as well as the persistence of southern species increasing the species richness. Range contraction were also observed among larger northern species, specially among fisheries targeted one. The reported range size changes will have ecological consequences, potentially affecting the ecosystems productivity and should be taken into account when developing future conservation and fisheries strategies in the future.},
  author       = {Fredricson, Jonatan},
  language     = {eng},
  note         = {Student Paper},
  title        = {Range size changes within the North Sea fish assemblage},
  year         = {2015},
}