Broadly I am interested in mathematical ecology and in particular I am interested in the dynamics of marine metapopulations and sea lice on salmon farms. Below are some short synopses of projects that I have been working on.
A next-generation approach to calculate source-sink dynamics in marine metapopulations:

            Calculating source and sink patches is important to preserve or control marine species where adult subpopulations remain confined to population patches, but larval dispersal can connect subpopulations. In this paper we applied a next generation approach specifically to sea lice populations on salmon farms, which have large economic effects on the salmon farming industry. 

Harrington, P.D., and M.A. Lewis, A Next-Generation Approach to Calculate Source–Sink Dynamics in Marine Metapopulations, Bull Math Biol 82, 9 (2020)

A framework for studying transients in marine metapopulations

Understanding the short-term dynamics that may occur in marine metapopulations is important in controlling the outbreak and spread of infections and invasive species.  In this paper we connected the short-term dynamics to the source-sink distribution of marine metapopulations so that existing knowledge on source and sink patches can be used to identify where outbreaks may occur.  


Harrington, P.D., Lewis, M.A. and P van den Driessche, Reactivity, attenuation, and transients in metapopulations, SIAM J. Appl. Dyn. Syst 21:2 (2022)

Next-generation matrices for marine metapopulations: the case of sea lice on salmon farms

In this paper we construct a next-generation matrix for a network of sea lice populations on salmon farms in the Broughton Archipelago, BC, an intensive salmon farming region on the west coast of Canada where certain salmon farms are currently being removed under an agreement between local First Nations and the provincial government. We identify the salmon farms which are acting as the largest sources of sea lice and show that in this region the most productive sea lice populations are also the most connected. We find that the farms which are the largest sources of sea lice have not yet been removed from the Broughton Archipelago, and that warming temperatures could lead to increased sea louse growth. The pre-print of this paper is available at:

Calculating arrival times for sea louse spread between salmon farms

Calculating the arrival times of sea lice spreading between salmon farms is important in controlling sea lice outbreaks in small areas with multiple salmon farms, which is typical of many salmon farming regions across the world. In this paper I used data from the Broughton Archipelago, BC to calculate these arrival times and determine how farm placement can affect the spread of sea lice. This paper will be submitted shortly.

Timing of infections of epidemics on networks of farms, cities, or individuals

In this paper we calculated the time of infection of any node on a network when the location of the initial infection is known. In the context of salmon farms each node represents one farm and the network represents how many sea lice can spread between different salmon farms. By calculating the time it takes for sea louse outbreaks to spread to other farms within the network we can better understand how to control sea louse outbreaks and other infections before they take off. This paper has been submitted.

Salmon Coast Field Station

Salmon Coast Field Station has been monitoring the abundance of sea lice on wild salmon for over 20 years. As part of my PhD I have participated in this long-term monitoring program at Salmon Coast for five years. In 2018 and 2019 I was the leader of this monitoring program and was responsible for the safety of field crew and writing the publicly available yearly reports which are available at