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Evolutionary pressures under the current fishing practices in European hake (Merluccius merluccius)

Jusufovski, Dunja (2013) BIOM35 20131
Degree Projects in Biology
Abstract
Abstract

There is a rising concern involving the impact of modern fisheries on the dynamics and viability of the exploited fish populations. The increasing fishing pressure has been recorded to cause declines in age and size at maturation in variety of marine fish species. In this study I have aimed to detect heritable phenotypic changes of the European hake (Merluccius merluccius) under the currently prevailing fishing intensity. Using dataset of 64 individual-based growth parameters of the studied species and an individual-based simulation, which incorporates quantitative genetics, ecological processes and biological characteristics, I have simulated ecological and evolutionary dynamics of hake. Species` phenotypic traits were... (More)
Abstract

There is a rising concern involving the impact of modern fisheries on the dynamics and viability of the exploited fish populations. The increasing fishing pressure has been recorded to cause declines in age and size at maturation in variety of marine fish species. In this study I have aimed to detect heritable phenotypic changes of the European hake (Merluccius merluccius) under the currently prevailing fishing intensity. Using dataset of 64 individual-based growth parameters of the studied species and an individual-based simulation, which incorporates quantitative genetics, ecological processes and biological characteristics, I have simulated ecological and evolutionary dynamics of hake. Species` phenotypic traits were observed through three different scenarios which showed significant ecological consequences for hake population under the current fishing strategies but detected no evolutionary changes in life-history traits, e.g. growth and age and size at maturation. Even though, the current fishing intensity does not appear to select for a specific life-history type, the ecological impact observed under under the current fishing practices can pose a severe risk through direct population declines. (Less)
Abstract
Popular science summary

Is the European hake “shrinking” under the current fishing practices?

Did you know that the current fishing practices have caused significant declines in body size of many exploited fishing stocks? This effect of fishing management has become one of the major threats for commercially exploited fish species and it can have severe negative consequences for the offspring of the species as well as the ecosystem`s stability.

As the demand for fish grows, the fishing gear, such as fishing nets, become more effective in harvesting older and bigger fish since they are the most valuable fish on the market. By removing these individuals, there is more food and space for smaller fish to grow and feed. This will... (More)
Popular science summary

Is the European hake “shrinking” under the current fishing practices?

Did you know that the current fishing practices have caused significant declines in body size of many exploited fishing stocks? This effect of fishing management has become one of the major threats for commercially exploited fish species and it can have severe negative consequences for the offspring of the species as well as the ecosystem`s stability.

As the demand for fish grows, the fishing gear, such as fishing nets, become more effective in harvesting older and bigger fish since they are the most valuable fish on the market. By removing these individuals, there is more food and space for smaller fish to grow and feed. This will eventually lead for the smaller ones to grow faster and achieve sexual maturity earlier than it occurs in populations not experiencing the pressure by fisheries.

As the fish matures earlier and at a smaller size, so does their offspring become smaller and such biological characteristics can become heritable over time. In the long run, these changes induced by fishing intensity, can cause higher variations in the population dynamics and, in the end, lead to population collapse.

Following this theory, I have investigated the state of European hake (Merluccius merluccius) stocks across geographic areas in order to detect whether current fishing practices are causing heritable changes in size and age at maturation. For this purpose, I have simulated fish populations and exposed them to three different scenarios which allowed me to compare the effects of: (a) non-fishing conditions, (b) fishing with and (c) without evolutionary processes.

Opposite of our expectations, the overall results of the simulations show a biologically nonsignificant decline in size and age at maturation for the European hake. However, the ecological impact of fisheries shows drastic drop in biomass and recruitment. In other words, the results of the study suggest that either the current fishing practices are not potent enough to induce heritable changes for this species or that hake`s specific life strategy has developed mechanisms that can counteract the effects of fishing. Nevertheless, currently prevailing fisheries management could pose a risk of loss through the severe population declines. Therefore, the results of this study should be interpreted with caution. There is a definite need to investigate further the processes that lie behind the observed resistance in populations of the European hake.

Advisor: Anna Kuparinen (University of Helsinki) and Per Carlsson
Master project 45 credits in Aquatic Ecology
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Jusufovski, Dunja
supervisor
organization
course
BIOM35 20131
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
4123499
date added to LUP
2013-10-24 14:11:00
date last changed
2014-05-16 10:24:44
@misc{4123499,
  abstract     = {Popular science summary

Is the European hake “shrinking” under the current fishing practices?

Did you know that the current fishing practices have caused significant declines in body size of many exploited fishing stocks? This effect of fishing management has become one of the major threats for commercially exploited fish species and it can have severe negative consequences for the offspring of the species as well as the ecosystem`s stability.

As the demand for fish grows, the fishing gear, such as fishing nets, become more effective in harvesting older and bigger fish since they are the most valuable fish on the market. By removing these individuals, there is more food and space for smaller fish to grow and feed. This will eventually lead for the smaller ones to grow faster and achieve sexual maturity earlier than it occurs in populations not experiencing the pressure by fisheries. 

As the fish matures earlier and at a smaller size, so does their offspring become smaller and such biological characteristics can become heritable over time. In the long run, these changes induced by fishing intensity, can cause higher variations in the population dynamics and, in the end, lead to population collapse.

Following this theory, I have investigated the state of European hake (Merluccius merluccius) stocks across geographic areas in order to detect whether current fishing practices are causing heritable changes in size and age at maturation. For this purpose, I have simulated fish populations and exposed them to three different scenarios which allowed me to compare the effects of: (a) non-fishing conditions, (b) fishing with and (c) without evolutionary processes.

Opposite of our expectations, the overall results of the simulations show a biologically nonsignificant decline in size and age at maturation for the European hake. However, the ecological impact of fisheries shows drastic drop in biomass and recruitment. In other words, the results of the study suggest that either the current fishing practices are not potent enough to induce heritable changes for this species or that hake`s specific life strategy has developed mechanisms that can counteract the effects of fishing. Nevertheless, currently prevailing fisheries management could pose a risk of loss through the severe population declines. Therefore, the results of this study should be interpreted with caution. There is a definite need to investigate further the processes that lie behind the observed resistance in populations of the European hake. 

Advisor: Anna Kuparinen (University of Helsinki) and Per Carlsson
Master project 45 credits in Aquatic Ecology
Department of Biology, Lund University},
  author       = {Jusufovski, Dunja},
  language     = {eng},
  note         = {Student Paper},
  title        = {Evolutionary pressures under the current fishing practices in European hake (Merluccius merluccius)},
  year         = {2013},
}