Research database

Project information
Keywords
benthos, modeling, scavenging
Project title
EFFECTS: Examining the role of Fish-Falls on ECosystem processes in highly exploiTed fjord Systems
Year
2017
Project leader
Paul Renaud
Geographical localization of the research project in decimal degrees (max 5 per project, ex. 70,662°N and 23,707°E)
69.8°N 18.7°E
Participants

 

Katherine Dunlop, Ole Anders Nøst, Qin Zhou (Akvaplan-niva)

 

Evgeniy Yakushev (NIVA)

 

Martin Biuw, Angelika Renner (Institute of Marine Research)

 

Andrew Sweetman (Heriot Watt University) (UK)

 

Daniel O B Jones (National Oceanography Centre) (UK)

 

Flagship
Fjord and Coast
Funding Source

Summary of Results

Within the past decade, a large proportion of the migrating Norwegian Spring Spawning herring stock has made an extended stopover in the fjords of Kvaløya. This has led to intense fishing efforts whereby over 90% of the Norwegian catch during this period has been in Kaldfjorden waters. In addition, hundreds of both killer whales and humpback whales have followed the herring to these coasts. The herring catch and whale tourism has added greatly to the local economy, but this superabundance of herring has led to mass mortality in salmon pens as the herring schools can reduce oxygen levels to lethal levels. High mortality levels in herring are suspected from predation, and it is likely that considerable numbers of dead and injured herring fall to the fjord floor after unsuccessful predation or fishing efforts. Large fish falls are found in oceans around the world, and can provide significant organic input to the benthic system. In fjords of the size of Kaldfjorden, this rapid flux of labile food from herring falls could have significant effects on the benthic system, but these effects have not been studied. Our objective in this Fram proposal is: to determine the impact of organic inputs from herring-falls on benthic community functioning.

 

This Fram project fits into the framework of our on-going JellyFarm project, which evaluates the consequences of the combined inputs of OM on ecosystem and socio-economic processes. To carry out this work we need to determine how much OM from herring falls reaches the seafloor, how quickly it is scavenged by fishes and hyperbenthic invertebrates, and then evaluate the effects of this net input on sediment community processes. We use a validated biogeochemical model (BROM, Yakushev et al. 2016) to identify the effects of multiple OM sources.

 

This report summarizes work performed specifically through EFFECTS, even though there is significant overlap with  the F&C weShare and WHALE projects. Please consult the specific reports for those projects for details.

 

      The main field work for this project will take place in early December 2017 from Johan Hjort. We will conduct yo-yo camera transect to determine the abundance of herring (and other organic falls) on the seafloor. At the same time, we will determine scavenging rates on herring carcasses using a baited time-lapse camera lander (Dunlop et al. in press). We conducted scavenger lander trials on Svalbard in August 2017 with great success (Fig. 1).

 

 

 

Figure 1. Scavenger lander being deployed on Svalbard (left), and remaining herring after 8 h deployments in two Svalbard fjords (right). Note herring being reduced to skeletons in the lower figure while remaining largely intact in the upper figure.

 

 

 

Results from Svalbard indicated large differences among fjords in scavenging intensity, which could have important implications for spatial differences in benthic processing of organic matter.

 

 

Hydrographic modeling will be performed in two ways, with the ROMS platform that uses identical square grids (160 m x 160 m), and the unstructured grid FVCOM platform. Gridding for both are complete (Fig. 2) and ROMS runs have begun (see WHALE annual report). FVCOM work and an intercomparison are scheduled for 2018, but modeling has already begun.

 

 

 

 

 

 

Figure 2. FVCOM grid set-up for the entire Troms coast (left), and the Kaldfjorden region (right, in the oval).

 

 

Master and PhD-students involved in the project

PhD student Robert Harbour (HWU). Several other MS and PhD students are involved indirectly through the JellyFarm, weShare, and WHALE projects.

For the Management

This study addresses ecosystem-relevant processes linked with community structure in a fjord system of high economic and social importance. The Kaldfjorden ecosystem has supported the coastal fishery for Norwegian spring-spawning herring in recent years, and a vibrant tourism industry around whale watching has built up over the past 5-7 years. Changing herring dynamics, as suggested by the absence of large herring schools thus far in 2017, indicates the need for a general understanding of the effects of herring on northern fjord systems for general understanding of their consequences. Management of the system for maximum sustainability in the face of multiple and fluctuating uses is only achievable through an integrated ecosystem understanding involving the physical environment, biotic communities, and the human dimension. This project provides such a multi-faceted perspective.

Published Results/Planned Publications

  1. Dunlop, Sweetman, Berge, Renaud. Scavenging activity in high Arctic fjords. in preparation, to be submitted summer 2018
  2. Renaud, Dunlop, Sweetman, Jones, Biuw et al. Inputs of organic matter from herring falls to a fjord basin.
  3. Yakushev, Nøst, Zhou, Sweetman, Renner, Renaud. Implications of multiple sources of organic matter on benthic ecosystem processes: insights from a combined hydrodynamic-geochemical model.
Communicated Results

The JellyFarm project runs a blog (http://jellyfarmproject.blogspot.no) where work from the combined F&C projects have been highlighted. In addition, we have published an article in Svalbardposten ('Se opp for disse når du bader!' Berge, Sweetman, Renaud, Dunlop, 25.08.2017) on scavenging in Svalbard fjords. This work was also profiled on Akvaplan-niva's Facebook site.

In addition, scavenging and the Svalbard experiments were well integrated into the recent Arctic Benthic Ecology course (AB321/821) at UNIS in Autumn 2017. Students learned the theory and practice of scavenging ecology and one of the course projects specifically dealt with this topic.

Interdisciplinary Cooperation

This project is one of three F&C projects studying aspects of the Kaldfjorden ecosystem. weShare (M Biuw) investigates herring populations, whale migration and feeding, and citizen science. WHALE (A. Renner) performs hydrodynamic modeling (ROMS and co-funds the FVCOM modeling this project also contributes to), water column sampling for nutrients and the CO2 system, and short-term vertical flux estimates on a monthly basis through the year. These different kinds of sampling and modeling complement the work done here and will be integrated in the BROM modeling framework.

 

Budget in accordance to results

Yes

Could results from the project be subject for any commercial utilization
No
Conclusions

The preliminary work for this project has been successful and we see no major problems conducting the field work in December 2017 as planned. Herring and whales have not re-entered Kaldfjorden in large numbers this year, so the immediate relevance of herring-falls is reduced, but the effects of organic fluxes on benthic processes, and scavenging on fish-falls, are highly relevant for many fjords. The larger context this project is placed in, both the combined F&C projects in Kaldfjorden and the JellyFarm project, will provide valuable information on ecosystem functioning and dynamics. So although it is a disappointment that herring are absent