Leigh Michael Howarth

Leigh Michael Howarth
Dalhousie University | Dal · Department of Oceanography

17.46
 · 
PhD Marine and Fisheries Science
About
13
Research items
4,855
Reads
134
Citations
Introduction
I work at Dalhousie University as a post-doctoral fellow investigating the ecological effects of salmon aquaculture. My main focus is using stable isotopes in macroalgae to map the effluent footprints of salmon farms located in eastern Atlantic Canada.
Research Experience
Mar 2018
Dalhousie University
Position
  • Postdoctoral Fellow
Description
  • Investigating the ecological effects of salmon aquaculture in Eastern Canada and further afield.
Oct 2017 - Mar 2018
The University of Sheffield
Position
  • Post-doctoral researcher
Description
  • Worked on a project deriving thermal traits for all marine species within Europe for the European Marine Observation and Data Network (EMODnet) using global databases such as the Oceanographic Biogeographic Information System (OBIS).
Apr 2015 - May 2017
Bangor University
Position
  • Research Officer
Description
  • I worked on the Marine Ecosystems Research Program (MERP), a £6 million multi-institutional project funded by NERC and Defra.
Education
May 2011 - Jun 2014
University of York
Field of study
  • Marine and Fisheries Science
Oct 2009 - Oct 2010
University of York
Field of study
  • Marine Environmental Managment
Sep 2006 - Jul 2009
University of East Anglia
Field of study
  • Ecology
Network
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Following
Projects
Projects (5)
Project
(1) To map the footprint of multiple effluent sources at the water-body level, using 15N isotopes in macroalage 'bioindicators'. (2) To gain greater insight into the dispersal of dissolved wastes emanating from salmon farms.
Project
Human activities such as the treatment of wastewater, farming and aquaculture can increase the nutrient loads of coastal waters. Although the environmental effects of these single sources are well documented, little is known about how these various sources interact. Hence, the Food and Agriculture Organisation (FAO) recently recommended a shift in the way we manage and monitor aquaculture; from the current approach where the small-scale effects of single farms are regarded, towards an Ecosystem Approach to Aquaculture where the effects of multiple farms and stressors are considered at a wider scale. Assessing the amount of dissolved nutrients emanating from effluent sources can be difficult as their concentrations display strong daily and seasonal fluctuations. Dissolved nutrients are also rapidly diluted and dispersed, meaning increases in their concentration tend to be very small, short-lived and difficult to detect. Lastly, effluents rarely occur in isolation, making it difficult to distinguish between different sources. In contrast, seaweeds and other marine plants readily absorb dissolved nutrients and accumulate it in their tissues. This means the nutrient composition of their tissues are less affected by fluctuations and may better reflect long-term nutrient levels. Another advantage is that different effluent sources often have distinguishable stable isotope compositions, which can create distinct isotope signatures in plant tissues, meaning there is potential to identify between them. In this project, we are planting seaweeds across a bay in Atlantic Canada. We are doing this to investigate how the effluents of a large industrial salmon farm interact with other effluent sources at a bay-wide scale.
Project
Identify the level of MP contamination in plaice, Pleuronectes platessa in the Irish Sea Compare the mass of ingested MP from areas of different fishing intensity Identify potential for trophic transfer by carrying out gut examination of whole prey items
Research
Research items (13)
Article
Full-text available
This study investigated the effects of a newly established, fully protected marine reserve on benthic habitats and two commercially valuable species of scallop in Lamlash Bay, Isle of Arran, United Kingdom. Annual dive surveys from 2010 to 2013 showed the abundance of juvenile scallops to be significantly greater within the marine reserve than outs...
Article
Full-text available
Many over-exploited marine ecosystems worldwide have lost their natural populations of large predatory finfish and have become dominated by crustaceans and other invertebrates. Controversially, some of these simplified ecosystems have gone on to support highly successful invertebrate fisheries capable of generating more economic value than the fish...
Chapter
Full-text available
Global landings of scallops have grown dramatically in recent decades and these fisheries are now among the most lucrative in several countries around the world. Despite this apparent success story, concerns have arisen about the wider ecosystem effects of scallop fisheries. This is particularly the case for the most common type of fisheries that u...
Article
Full-text available
This study investigated the effects of a community-led temperate marine reserve in Lamlash Bay, Firth of Clyde, Scotland, on commercially important populations of European lobster (Homarus gammarus), brown crab (Cancer pagurus), and velvet swimming crabs (Necora puber). Potting surveys conducted over 4 years revealed significantly higher catch per...
Article
Although many studies have investigated the effects of disturbance and environmental drivers on marine ecosystems, comparatively few have studied their interactions. Using fuzzy coded biological traits, we compared the functional composition, diversity and evenness of benthic communities in the English Channel and in the Celtic and Irish Seas acros...
Article
Understanding links between habitat characteristics and foraging efficiency helps predict how environmental changes influence populations of top predators. This study examines whether measurements of prey (clupeids) availability varied over stratification gradients, and determined if any of those measurements coincided with aggregations of foraging...
Poster
Full-text available
Traditionally, marine ecosystems have been described through indices of species composition, diversity and abundance. However, such studies often result in “noisy data”, which is very difficult to interpret and draw any solid conclusions. This is because marine ecosystems are incredibly complex and dynamic. “Size spectra” based approaches have ther...
Technical Report
Full-text available
The king scallop fishery is the fastest growing fishery in the UK and currently the second most valuable. The UK is also home to the largest queen scallop fishery out of all of Europe. However, concerns have been raised about the effects of this recent growth of UK scallop fisheries among scientists and conservation bodies, as well as amongst the p...
Article
Full-text available
Despite the implementation of several precautionary management measures in Scotland, evidence suggests that scallop fisheries based in the Firth of Clyde may not reach long-term sustainability. It is argued that only the establishment of No take Zones (NTZs) can restore the age structure and spawning biomass of scallop stocks. The aim of this study...
Article
Full-text available
This study investigated the effects of a fully protected marine reserve on commercially valuable scallops and benthic habitats in Lamlash Bay, Isle of Arran, United Kingdom. Dive surveys found the abundance of juvenile scallops to be greater within the marine reserve than outside. A novel multivariate approach, based upon neural networks and genera...