About the lab
Research activity being conducted at the Norwegian Institute of Marine Research by Howard Browman, Anne Berit Skiftesvik, Caroline Durif, Kim Halvorsen, Reidun Bjelland, David Fields, and our students, Post-Doctoral Associates, Research Associates, and Collaborators.
Featured projects (2)
CoastVision will use the power of deep learning to refine and extend a computer vision pipeline for detecting, classifying and sizing the key fish species in shallow water coastal ecosystems, facilitating a transition to fully automated video analysis. Our models will be trained on data sets from several different surveys, ensuring cost-efficient development of routines that will be widely applicable. Computer vision for re-identifying (re-ID) individuals solely based on their unique visible features will also be developed. This novel aspect of CoastVision could ultimately provide new opportunities to obtain detailed knowledge about behaviour and population dynamics in wild fish populations, with minimal negative impact on animals and habitats and at a low cost. Our focal species for re-ID are Atlantic cod, ballan wrasse and corkwing wrasse, commercially important species with complex, high-contrast skin patterns. To generate the necessary training data for re-ID we will use synchronized radio frequency identification and camera systems. CoastVision’s automated video analysis pipeline will be integrated into ongoing ecosystem surveys and case studies whose main objective is to better understand the factors that affects the reproduction, recruitment and survival of commercially important coastal species. As such, CoastVision will contribute to independent, but complementary, research objectives. The project will advance the international research front for applied machine learning in marine ecology, which ultimately can revolutionize our ability to observe, understand and respond to ecological change at scales far more refined than is currently possible.
Wrasses are intensively harvested in Scandinavia and on the British Isles, where they are deployed as cleaner fish in salmon farms. What are the consequences for wrasse populations and the coastal ecosystems? Main objectives: 1. Selective harvesting: Understanding how selective fisheries affect species composition, phenotypic distributions and the consequences for population dynamics and mating patterns. Contrasting slot-size limits vs. minimum size limits. 2: Eco-effects: Investigating the wider ecosystem effects of depleting wrasse populations. 3: Consequences of translocations: What happens when wrasse escapes into genetically distinct populations?
Featured research (12)
High Voltage Direct Current (HVDC) subsea cables are used to transport power between locations and from/to near-shore and off-shore facilities. HVDC cables produce magnetic fields (B-fields) that could impact marine fish. Atlantic haddock (Melanogrammus aeglefinus) is a demersal fish that is at risk of exposure to anthropogenic B-fields. Their larvae drift over the continental shelf, and use the Earth's magnetic field for orientation during dispersal. Therefore, anthropogenic MFs from HVDC cables could alter their behavior. We tested the behavior of 92 haddock larvae using a setup designed to simulate the scenario of larvae drifting past a B-field in the intensity range of that produced by a DC subsea cable. We exposed the larvae to a B-field intensity ranging 50-150 μT in a raceway tank. Exposure to the B-field did not affect the spatial distribution of haddock larvae in the raceway. Larvae were categorized by differences in their exploratory behavior in the raceway. The majority (78%) of larvae were non-exploratory, and exposure to the artificial B-field reduced their median swimming speed by 60% and decreased their median acceleration by 38%. There was no effect on swimming of the smaller proportion (22%) of exploratory larvae. These observations support the conclusion that swimming performance of non-exploratory haddock larvae would be reduced following exposure to B-field from HVDC cables. The selective impact on non-exploratory individuals, and the lack of impact on exploratory individuals, could have population-scale implications for haddock in the wild.
Like many animals, northern temperate eel can enter a hibernation-like state and become dormant during the winter. Knowledge of overwintering behaviour in eel is sparse and mainly based on anecdotal observations and a few experimental studies on thermal tolerance. We studied European eel (Anguilla anguilla) overwintering behaviour in a Skagerrak fjord in Southern Norway, during three consecutive years, using an array of acoustic receivers and acoustic tags with depth and temperature sensors. We obtained results from 55 yellow eel, of which 19 were studied for one winter, 35 for two winters and one for three winters. Dormancy was inferred to begin in September for the earliest individuals and lasted until May for the last, with the majority of eel dormant from at least late October–November until mid-April. The timing of dormancy was mainly related to photoperiod and less to temperature. More than 50% of eel became dormant when day length was <9 hours and became active when day length was >14 hours. Approximately 10% of eel remained active during the winter and 31% of eel changed their pattern between consecutive years. Some dormant individuals exhibited activity periods that interrupted their dormancy. Eel in the outer fjord nearer the open sea became dormant before eel in the inner more freshwater part of the fjord, and were dormant longer.
In the North Sea, the number and size of offshore wind (OW) turbines, together with the associated network of High Voltage Direct Current (HVDC) subsea cables, will increase rapidly over the coming years. HVDC cables produce magnetic fields (MFs) that might have an impact on marine animals that encounter them. One of the fish species that is at risk of exposure to MF associated with OW is the lesser sandeel (Ammodytes marinus), a keystone species of the North Sea basin. Lesser sandeel could be exposed to MF as larvae, when they drift in proximity of OW turbines. Whether MFs impact the behavior of lesser sandeel larvae, with possible downstream effects on their dispersal and survival, is unknown. We tested the behavior of 56 lesser sandeel larvae, using a setup designed to simulate the scenario of larvae drifting past a DC cable. We exposed the larvae to a MF intensity gradient (150-50 μT) that is within the range of MFs produced by HVDC subsea cables. Exposure to the MF gradient did not affect the spatial distribution of lesser sandeel larvae in a raceway tank 50 cm long, 7 cm wide and 3.5 cm deep. Nor did the MF alter their swimming speed, acceleration or distance moved. These results show that static MF from DC cables would not impact behavior of lesser sandeel larvae during the larval period of their life although it does not exclude the possibility that later life stages could be affected.
The goldsinny wrasse (Ctenolabrus rupestris) is a commercially important fish that inhabits coastal areas across the eastern Atlantic. This species moves from a shallow home territory along the coast into deeper waters in the autumn and winter and then returns to that same territory in the spring. Only male goldsinny wrasse exhibit strong territorial behavior, which may manifest as sexual differences in the ability or motivation to return to home territories. The orientation mechanism underlying the homing migration of goldsinny wrasse males and females is unknown. In this study, we hypothesized that goldsinny wrasse use the magnetic field of the Earth to follow a compass‐based path toward their home territory. To test this hypothesis, we collected 50 adult goldsinny wrasse, approximately half males and half females, in a harbor in Austevoll, Norway. Fish were translocated to a magnetoreception laboratory situated north of the site of capture, in which the magnetic field was artificially rotated. In the laboratory, males oriented toward the magnetic south taking a mean direction of 201°, which is the approximate direction that they would have had to take to return to the site at which they were captured. Females oriented in random magnetic directions. There was no difference in swimming kinematics between males and females. These results show that male goldsinny wrasse have a magnetic compass that they could use to maintain site fidelity, an ability that could help them and other coastal fish undertake repeatable short‐range migrations.
Anguillid eels grow in freshwater but spawn in the open ocean. The cues that guide eels over long distances to the spawning area are unknown. The Earth's magnetic field can provide directional and positional information and is likely used by catadromous eels during their spawning migration; as magnetosensitivity and compass orientation have been reported in eels. To test whether this is theoretically possible, we compared the migratory routes of five species of temperate eels that undertake long migrations with the geomagnetic field of their distribution/spawning areas. We found that, regardless of the species and although routes are different between life stages, larvae of those species always drift along paths of increasing magnetic inclination and intensity, while adults follow reverse gradients. This is consistent with an imprinting/retracing hypothesis. We propose a general navigation mechanism based on larvae imprinting on a target magnetic intensity (or inclination) at the hatching area and on the intensity (or inclination) gradient during larval drift. Years later, adults retrace the magnetic route by following the gradient of decreasing total intensity (or inclination) values that occurs towards lower latitudes. As they reach the target value, adults switch to compass orientation to stay on the target isoline and reach the spawning area. The proposed mechanism fits for all temperate eels examined. Knowledge about navigational strategies of eels is important to evaluate the effectiveness of management strategies that involve stocking of juveniles displaced from one area to another to rebuild local populations.
- Research Group of Observation Methodology
About Howard Browman
- Howard Browman has been a Principal Research Scientist with the Institute of Marine Research in Bergen, Norway since 1998. He has published > 100 articles, books and edited volumes and has delivered hundreds of lectures and conference/symposium/workshop presentations. For more information, see: http://fishlarvae.com/people/howard-i-browman/