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The Role of Physiology in the Causes and Consequences of Fisheries-Induced Evolution

Periodic Reporting for period 3 - PHYSFISH (The Role of Physiology in the Causes and Consequences of Fisheries-Induced Evolution)

Reporting period: 2018-05-01 to 2019-10-31

There is increasing evidence that intense commercial fishing pressure is not only depleting fish stocks but also causing evolutionary changes to fish populations with serious consequences for the viability of marine fish communities. Overlooked within the context of fisheries-induced evolution (FIE) is the likelihood that, within a given species, variation in physiological traits among individuals – and especially those related to energy balance (e.g. metabolic rate) and swimming performance (e.g. aerobic scope) – could make some fish more catchable or more likely to suffer mortality after discard. Selection on these traits could produce major shifts in the fundamental structure and function of fish in response to fishing pressure that are yet to be considered but which could directly determine population resource requirements, resiliency, geographic distributions, and responses to environmental change. This pioneering project will address this gap in knowledge with three main goals: (1) to examine whether physiological traits make some individuals more catchable by commercial fishing gears, and whether the environment modulates such effects; (2) to investigate the extent to which physiological traits influence recovery and survival after escape from fishing gear or discard; and (3) to determine whether selection on catchability generates changes in physiological traits that reduce population resiliency or erode the ability to cope with environmental change. Given that several fisheries have not recovered despite lengthy moratoriums, there is a pressing need to understand the long-term physiological effects of FIE on fish stocks and their capacity to rebound after fishing pressure is lifted. The aims of this project are ambitious but this information is vital for truly understanding the mechanisms of FIE and its consequences for stock sustainability and the function of marine ecosystems.

Main Objectives
This project will use laboratory simulations of fisheries gears and practices, coupled with field studies using telemetry to track the habitat use and behaviour of fish around gears in the wild, to answer three main questions:
(1) Do physiological traits make some individuals more catchable?
a. Do physiological traits associated with metabolic demand and swimming ability make some individuals more likely to encounter, avoid, or escape passive and active fishing gears?
b. To what degree is catchability repeatable among individual fish?
c. Does the environment modulate the intensity or direction of selection by fishing gears via effects on individual physiological traits?
(2) Do physiological traits make some individuals more likely to experience mortality after escape from gear or discard?
a. Do physiological traits affect the degree of stress experienced by individuals during escape and discard, as well as their ability to recover from these stresses?
b. Does the environment modulate the influence of physiological traits on the recovery ability in escaped or discarded fish?
(3) Does selection on catchability generate correlated changes in physiological traits?
a. Does the direction or intensity of selection vary between active and passive gears?
b. Does selection for catchability alter physiological sensitivity to temperature and oxygen availability?
c. Does selection have long-term effects on physiological traits and tolerance to the environment that persists even after fishing is removed?
To date the project has been progressing successfully with a few postponements and adjustments. Major achievements include:
1) The production of a laboratory-based apparatus for the simulation of fishing by trawl and trap. Establishment of the trawl simulations was especially elaborate with the installation of a large flume tank and a custom-built miniature trawl net.
2) The establishment of wild zebrafish selection lines. This process included the installation of two purpose built zebrafish rearing racks as well as six large stock tanks. Wild zebrafish were obtained and the first generation has been bred successfully. After this point, however, disease arose within the population and so this aspect of the project was restarted with new fish.
3) The installation of an acoustic telemetry array for tracking the behaviour of wild fish. 30 wild perch have been released into the array and we have completed our data download. Analysis of this data is underway and will provide the first information on links between physiological traits and habitat selection in wild, free-ranging fish.
4) The completion of five sets of experiments to examine how physiology interacts with social influences to determine vulnerability to capture by trap and trawl. These experiments were completed by PhD students on the project.
5) From the perspective of staff hirings, one technician, one postdoc, and two PhD students were hired onto the project. In the original proposal only one PhD student was intended to start in the first year but two excellent candidates were in the first hiring pool and so both were hired. This has turned out to be a great outcome because the establishment of the zebrafish populations have gone much more smoothly with the addition of the second PhD student.
Notable delays and project changes are as follows:
1) The acoustic array has been installed in a freshwater Loch system instead of a marine system. We chose to go with this option first in order to test the system and provide data for a later installation of the array in a larger system. However, we plan to transfer the array in to the marine realm later in the Autumn of 2018.
2) Some of the work for WP3 has been delayed because the postdoc on the project obtained permanent employment in another position and so the position needed to be re-filled. The new postdoc started in March 2017 and experiments for WP3 are underway.