Lumpfish (Cyclopterus lumpus) migrate from their offshore feeding areas to the coastal areas of Iceland during March and April where they remain for several months before spawning. Their movements during this time are poorly documented. Using the results of an extensive tag-recapture study (the largest documented for lumpfish) which took place between 2008 and 2014, the movement of female lumpfish around Iceland was investigated and the implications for fisheries management were considered. Of 9710 female fish tagged, 880 were recaptured and 82 of these were recaptured after more than 250 days at liberty (DAL). There was a negative relationship between length at tagging and recapture rate indicating that between 2008 and 2014, the fishery was selecting for smaller fish. Lumpfish showed extensive movements with fish tagged in coastal areas being recaptured up to 587 km from their tagging location and were capable of swimming up to 49 km day−1. Fish were most frequently caught in the area in which they were tagged; however, movement between areas was common. There were indications of homing behaviour with 75% of the fish, which were recaptured after 250 DAL, caught within 80 km of their tagging location. Fish which were tagged offshore before the fishing season showed no clear pattern of where they would be recaptured. These extensive movements and homing behaviour are discussed in the context of the management of the lumpfish fishery.

Lumpfish, or lumpsucker, Cyclopterus lumpus (Linnaeus, 1758) is widely distributed in the North Atlantic Ocean. It has a considerable economic value and substantial fisheries occur in several North Atlantic regions owing to the use of its fully ripe internal egg masses in the ovaries as an alternative to sturgeon caviar. Despite being intensively fished in several locations, biological knowledge is limited and no genetic structure information is available. In this study, the stock structure of C. lumpus was investigated across the North Atlantic using ten microsatellite loci. Out of ten loci, two exhibited higher level of differentiation but their inclusion/exclusion from the analyses did not drastically change the observed genetic pattern. A total of three distinct genetic groups were detected: Maine–Canada–Greenland, Iceland–Norway and Baltic Sea. These results, discussed in terms of origin of differentiation, gene flow, and selection, showed that gene flow was rather limited among the detected groups, and also between Greenland and Maine–Canada.

Little is known about the role of chemotaxis in the location and attachment of chytrid zoospores to potential diatom hosts. Hypothesizing that environmental stress parameters affect parasite-host recognition, four chytrid-diatom tandem cultures (Chytridium sp./Navicula sp., Rhizophydium type I/Nitzschia sp., Rhizophydium type IIa/Rhizosolenia sp., Rhizophydium type IIb/Chaetoceros sp.) were used to test the chemotaxis of chytrid zoospores and the presence of potential defense molecules in a non-contact-co-culturing approach. As potential triggers in the chemotaxis experiments, standards of eight carbohydrates, six amino acids, five fatty acids, and three compounds known as compatible solutes were used in individual and mixed solutions, respectively. In all tested cases, the whole-cell extracts of the light-stressed (continuous light exposure combined with 6 h UV radiation) hosts attracted the highest numbers of zoospores (86%), followed by the combined carbohydrate standard solution (76%), while all other compounds acted as weak triggers only. The results of the phytochemical screening, using biomass and supernatant extracts of susceptible and resistant host-diatom cultures, indicated in most of the tested extracts the presence of polyunsaturated fatty acids, phenols, and aldehydes, whereas the bioactivity screenings showed that the zoospores of the chytrid parasites were only significantly affected by the ethanolic supernatant extract of the resistant hosts.

Abstract:The influence of environmental factors on the infection susceptibility of four different marine diatom host species to chytrid infection was tested under laboratory conditions, using host and parasite isolates obtained from diverse coastal areas in north-west Iceland in 2015. Specifically, a total of 120 monoclonal marine diatom host cultures of Navicula, Nitzschia, Rhizosolenia and Chaeto ceros were exposed to their chytrid parasites Chytridium type I and Rhizophydium type I and II in Hellendahl glass staining jars which were subdivided in two compartments by nylon filters (mesh size 5 μm). ) and photoperiods (24 h dark, 8:16 h, 16:8 h light:dark and 24 h light) after 168 h exposure, using the one-factor-at-a-time method. In addition, growth rates and proline concentrations of the noninfected monoclonal host cultures were determined. In most cases, decreasing growth rates during the acclimatisation process to abiotic stressors were directly related to increases of proline in the host cells. Significant positive associations of infection densities to cell based proline concentrations were predominantly observed in the high-PFR assays and 24-h daylight treatments. At least for half of the tested host-parasite pairs, positive correlations of proline and parasite prevalence were found. In addition, chytrid abundance was also positively correlated with host densities of Navicula sp., Rhizosolenia sp. and Chaetoceros sp. Only in Nitzschia sp., was parasite density negatively associated with proline and showed no significant relationship to host densities, suggesting that other physiological/biochemical factors related to stress might have an impact on the susceptibility of this peculiar host diatom species.

This report documents the fishery, assessment, and management of lumpfish (Cyclopterus lumpus) across its distribution range. Targeting lumpfish for their roe on a large scale began in the 1950s in Iceland and Norway and then in Canada in the 1970s and Greenland in the 1990s. When the fishery began, there were few regulations, but limits on vessel size, mesh size, number of nets, and length of the fishing season were gradually implemented over time. Worldwide landings have varied from ca. 2000 to 8000 tonnes of roe between 1977 and 2016. Iceland and Canada accounted for >80% of the landings until 2000. After 2013, Greenland and Iceland accounted for >94%. All countries except Iceland show a decreasing trend in the number of boats participating in the fishery, which is related to several factors: the monetary value of the roe, changes in the abundance of lumpfish, and increasing age of artisanal fishers. Each country has a different combination of data available for assessment from basic landings and fishing effort data to more detailed fishery independent survey indices of abundance. The management of total catch also differs, with an effort-controlled fishery in Iceland and Canada, a total allowable catch (TAC) per boat in Norway, and TAC per area in Greenland. Population abundance is above management targets in Iceland and Norway, but the status is less clear in Greenland and around Denmark/Sweden and appears to be depleted around Canada. Certification by the Marine Stewardship Council was instrumental in the adoption of a management plan in Greenland; however, benefits to the fishers remain unclear. Aspects surrounding the biology of lumpfish, which is poorly understood and requires investigation, include growth rate, natural mortality, and population differentiation. In addition, there is concern about the potential impacts that the recent escalation in production of lumpfish for use as cleaner fish in the aquaculture industry could have on the wild population.