Do oceanographic characteristics and predator-prey behaviours define critical marine habitats?

Lead Research Organisation: University of Aberdeen
Department Name: Inst of Biological and Environmental Sci


The role of how we manage our seas is changing rapidly. The past approach was that of single species management, devoid of many environmental aspects, and without direct input from the fishing industry. That approach has been found wanting with many stocks fished at unsustainable levels. The way forward has been to recognise that we need to manage using an ecosystem based approach while at the same time maintaining direct interaction with the fishing industry in management decisions. Such an ecosystem approach requires a more mechanistic understanding of the role the physical environment plays whilst also taking into account multiple species interactions. It is also clear, as more demand is put upon the space use of our marine systems (i.e. offshore renewable developments, Marine Protected Areas and fishing effort becomes managed more on a spatial basis), a better understanding of the role of marine habitat is essential. This is particular difficult as marine habitat can move in both space and time. However, any fisherman can tell you that there are some locations (and times) that are almost always better than others for good catches. The understanding as to why that may be is a fundamental challenge. In earlier studies involving both the PI and Co-PI, in the North and Celtic Seas, we have found that in locations where there are disproportionately high numbers of seabirds, marine mammals or fishing effort, there are also spatially limited patches of high levels of sub-surface primary production. The patches appear to be associated with topographically-driven internal waves whose physical effects may be responsible for localised increases of primary production and the physical aggregation of smaller marine organisms. Therefore these features could be responsible for the predicable areas of foraging due to complex links in the entire food web (Hypothesis A) or just enhance the ability of predators to capture prey (fish) in these locations (Hypothesis B). The sub-surface signature of these areas has meant that they have been overlooked in studies which have identified important surface features, such as thermal fronts, known to contain aggregations of many marine species. These patches therefore represent a newly-identified class of spatially important locations in shallow seas. In this project we propose to test between Hypothesis A & B using a new survey framework that incorporates all of those factors and defines the critical characteristics of the marine habitat where multi-species (predator-prey) interactions and fisheries operations are more likely to occur. This survey framework is based, to some degree, on the tried and tested method that fishermen have used for centuries: i.e. to observe seabird and marine mammal behaviour as a guide to locations of fishing grounds. Our aim is to take that practice forward with a multi-disciplinary approach between marine ecologists (U. Aberdeen), biological and physical oceanographers (POL), statutory agencies (FRS, CEFAS, JNCC) as well as fishermen (CFPO) and a range of skilled marine animal and fisheries observers (JNCC, MRAG). This project also represents a unique opportunity, to more fully utilise a NERC Oceans2025 Project. In this interdisciplinary approach we will combine the continuous physical and biological oceanographic features that will be studied in the Oceans2025 program with the additional collection of acoustic sonar backscatter, visual observations of seabirds and marine mammals, vocalisations of cetaceans, fishery observations, and longer term fisheries and marine animal survey data. With these combined data products, we will identify and define the characteristics of these sub-surface patches and the bio-physical mechanisms that may lead to the facilitation of predator-prey interactions. This research will greatly enhance the type of mechanistic understanding needed for implementing the ecosystem approach to sustainable fisheries management.


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Martinez I (2013) The fish and fisheries of Jones Bank and the wider Celtic Sea in Progress in Oceanography

Description Public Summary of CMarHab (Critical Marine Habitats)
The role of managing our seas is changing rapidly as more demand is placed upon the use of space in the marine environment. It is essential to have a detailed understanding of how the motion and physical properties of seawater (physical oceanography) influence the biological productivity of the oceans, whether plankton (the microscopic life in the ocean), fish, seabirds or even fishermen. Any fisherman will tell you that there are some locations and times that consistently produce areas with large catches. Often these areas are located by fishing where there are large numbers of feeding seabirds or marine mammals. This co- location of many marine animals in space and time indicate that these areas are extremely ecologically important and are the limited locations where multiple levels of predator-prey interactions occur. Understanding and defining the spatial and temporal nature of these critical marine habitats is a fundamental challenge.
Our research in the North Sea suggested that areas of critical marine habitat (i.e. locations with lots of feeding seabirds & marine mammals) are associated with high levels of sub-surface primary production (i.e. planktonic plants) possibly driven by internal waves (underwater waves) which greatly increases local mixing. Internal waves are created by the combination of tidal currents, a stratified water column (where sun-warmed water separates out from colder deeper water) and the steepness of bank edges. The sub-surface signature of these areas has meant that they are not easily identified and ways to identify and define them are urgently needed.

Our first aim was to determine the exact physical role of seabed topography in creating internal waves and what conditions were needed for high predator-prey aggregations. Our second aim was to test innovative new repeated circular and 'on the spot' survey method that re-sampled the same area of predator-prey interaction at different tidal speeds in regions of contrasting topography; a steep bank and a flat site. Both surveys used acoustic and oceanographic instruments to record changes in physical and behavioural aspects, second by second.

The findings of the project are of significant interest. Where circular surveys were deployed in the North Sea, the main prey species, sand-eels, clearly modified their schooling behaviour with changes in the tidal speeds. As the water reaches maximum speeds the fish move higher in the water column, grouping themselves together in large numbers of shoals. This suggests that increased tidal speeds not only create large prey aggregations, but also increase the probability of interaction with predators (such as surface-feeding birds like kittiwakes) by drawing them towards the surface.

Results from the Celtic Sea surveys, focusing on increases in primary production suggest that higher turbulence affected the abundance of planktonic algae species and that tidal currents export this increased production to a much larger area around a bank. Evidence from both a sub-sea camera and fishing vessels showed that the fish species richness was higher on the bank than the flat sites even though there was only a 15 km difference between these locations. Internal waves were found in only one location on the bank and feeding gannets targeted this exact location which confirms that visible top predators are using aspects of internal wave activity. These combined results have direct implications for the definition and the spatial scale of what constitutes a 'critical habitat' for marine species.
This project has provided information linking fish distributions on a fine scale with the physical and biological environment which will allow more certainty in marine spatial management of fishing as well as increased certainty in the selection and location of SPA and SACs and the design of MPAs
Exploitation Route Marine spatial planning and MPAs: Marine spatial planning and the design of MPAs can only precede with certainty by understanding, in detail, the critically important spatial needs of marine animals. These results are needed by JNCC to underpin the advice they give to the nature conservation agencies about the selection and location of Special Protection Areas in the marine environment for seabirds, as required under the EU Birds Directive.

'Blue skies' - Ecological theory and analytical advances. Identifying the actual physical and/or biological mechanisms that lead to top predator-prey aggregations is, cutting edge ecological research. We have shown there are similarities across species groups in this study which goes some way in providing a generalised understanding of how and why areas with high sub-surface chlorophyll levels are important to multiple trophic levels and their role in marine ecosystem functioning. The analytical approach, in which we will be identifying the characteristics of spatial and temporal patterns of predator- prey interaction, is also advancing the analyses of spatial and temporal multivariate data.

Marine spatial planning and Renewables: Marine spatial planning and the location of Renewable developments can only precede with certainty by understanding, in detail, the mechanisms behind critically important spatial needs of marine animals (i.e. foraging areas and how the water column features are used for foraging)and how the effects of renewable devices may influence mechanisms. This presentation uses some of the results from this project to hypothesize what possible influences marine renewables can have.

New survey methods that underpin the ecosystem approach: The surveys tested in this project covering compatible, synoptic measurements of turbulence through to fishing activity and seabirds are new to ecosystem research. This research has provided new insights into the interaction of multiple marine trophic levels. The mechanistic level of understanding will bring benefits to a wide range of statutory, conservation and applied organisations as well as improve ecological understanding of marine ecosystems function.

Spatial fishing effort and the fishing industry: One of fisheries managements' most effective tools to ensure sustainable fisheries is to enforce changes to fishing effort. However, to make the most of changes in fishing effort, decisions need to be based on a clearer understanding of fish spatial and temporal habitat usage. The project provides a link with fish distributions on a fine spatial scale with other physical and biological drivers. Clearer understanding of spatial and temporal causes for the high variance in both survey and commercial catches will lead to greater certainty in abundance estimates.
Sectors Education,Energy,Environment,Government, Democracy and Justice

Description This research has increased the level of certainty that the foraging habitats of mobile marine species can be predicted using a range of seasonal and static bio-physical characteristics. This allows a mechanistic understanding of how and under what physical conditions energy is transferred across trophic levels and more accurate predictions of the potential effects of climate change on the spatial distribution of mobile marine animals. It also allows predictions of efficiency of trophic transfer in future climates. The understanding of how predators are using the environment to capture their prey will also allow a step change in predicting how wet renewables devices may affect marine animals and help engineers to design tidal, wave and wind farms which keep the risk of mortality and critical habitat change to a minimum. For years fisheries science has focused on dealing with high levels of variance in survey results, but not focused on the possible causes of that variance. This project's illumination of the linkage between tidal state (daily and monthly) and behaviour of marine animals (and fishermen) can vastly reduce the current high level of uncertainty in fisheries survey results by explaining the variance in spatial & temporal distribution and creating predicable changes in catchability. The linkage of top predator foraging to tidal state will also help to reduce variance in EIA studies currently being run for offshore wet renewable developments. These results will allow more certainty in marine spatial management of fishing as well as increased certainty in the selection and location of Natura sites, Marine Protected Areas and the locations for marine renewables.
First Year Of Impact 2010
Sector Education,Energy,Environment,Government, Democracy and Justice
Impact Types Policy & public services

Description Location of Marine Protected Areas and Marine Renewable Developments
Geographic Reach National 
Policy Influence Type Citation in other policy documents
Impact The overall results of this work will allow better allow more certainty in marine spatial management of fishing as well as increased certainty in the selection and location of Natura SPA and SACs, the design of Marine Protected Areas (MPAs) and the locations for marine renewable developments. This knowledge is being immediately implemented at the policy level for marine spatial planning issues as the PI is both on the Scientific Advisory Committee of Scottish Natural Heritage (SNH) and a member of the ministerial DEFRA Scientific Advisory Panel for the Network of Marine Protected Areas.
Description Future work and Funding resulting from the research
Amount £332,412 (GBP)
Funding ID FLOWBEC NE/J004332/1 and RESPONSE NE/J004340/1 
Organisation Research Councils UK (RCUK) 
Sector Public
Country United Kingdom
Start 09/2011 
End 09/2014
Description Future work and Funding resulting from the research
Amount £332,412 (GBP)
Funding ID FLOWBEC NE/J004332/1 and RESPONSE NE/J004340/1 
Organisation Research Councils UK (RCUK) 
Sector Public
Country United Kingdom
Start 09/2011 
End 08/2014