Modelling drift of pelagic offspring: the importance of egg surveys in providing a realistic model initialization

Espeland, Sigurd Heiberg; Albretsen, Jon; Olsen, Esben Moland; Bodvin, Torjan

doi:10.1093/icesjms/fsv134

Cited by 12 publications

(9 citation statements)

References 38 publications

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“…Figure 1B) most likely limit the exchange of deep and intermediate water masses between their basins. However, Espeland et al (2015) used nested ocean circulation models to show that surface water could be displaced north-eastwards from Lyngenfjord through the narrow sounds between the two fjords. Similar hydrographic conditions in the upper ∼170 m of the water column ( Supplementary Figures S3, S4, Results section) are probably a result of regional oceanographic processes involving coastal water masses influencing both fjords at intermediate depths in a near identical manner.…”

Section: Local Oceanographic Processesmentioning

confidence: 99%

Coincident Mass Occurrence of Gelatinous Zooplankton in Northern Norway

et al. 2018

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In autumn 2015, several sources reported observations of large amounts of gelatinous material in a large north Norwegian fjord system, either caught when trawling for other organisms or fouling fishing gear. The responsible organism was identified as a physonect siphonophore, Nanomia cara, while a ctenophore, Beroe cucumis, and a hydromedusa, Modeeria rotunda, were also registered in high abundances on a couple of occasions. To document the phenomena, we have compiled a variety of data from concurrent fisheries surveys and local fishermen, including physical samples, trawl catch, and acoustic data, photo and video evidence, and environmental data. Because of the gas-filled pneumatophore, characteristic for these types of siphonophores, acoustics provided detailed and unique insight to the horizontal and vertical distribution and potential abundances (∼0.2-20 colonies•m −3) of N. cara with the highest concentrations observed in the near bottom region at ∼320 m depth in the study area. This suggests that these animals were retained and accumulated in the deep basins of the fjord system possibly blooming here because of favorable environmental conditions and potentially higher prey availability compared to the shallower shelf areas to the north. Few cues as to the origin and onset of the bloom were found, but it may have originated from locally resident siphonophores. The characteristics of the deep-water masses in the fjord basins were different compared to the deep water outside the fjord system, suggesting no recent deep-water import to the fjords. However, water-masses containing siphonophores (not necessarily very abundant), may have been additionally introduced to the fjords at intermediate depths, with the animals subsequently trapped in the deeper fjord basins. The simultaneous observations of abundant siphonophores, hydromedusae, and ctenophores in the Lyngen-Kvaenangen fjord system are intriguing, but difficult to provide a unified explanation for, as the organisms differ in their biology and ecology. Nanomia and Beroe spp. are holopelagic, while M. rotunda has a benthic hydroid stage. The species also have different trophic ecologies and dietary preferences. Only by combining information from acoustics, trawling, genetics, and local fishermen, were the identity, abundance, and the vertical and horizontal distribution of the physonect siphonophore, N. cara, established.

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Section: Local Oceanographic Processesmentioning

confidence: 99%

Coincident Mass Occurrence of Gelatinous Zooplankton in Northern Norway

et al. 2018

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“…To the best of our knowledge, this study is the first to investigate driver mechanisms for the interannual variability in advection processes that affect Calanus stock size on the Lofoten‐Vesterålen shelf. Most of the particle tracking studies conducted along the Norwegian coast focused on different areas and the drift of fish eggs (Asplin et al ., ; Myksvoll et al ., ; Espeland et al ., ). In contrast, our approach focused on the importance of advection of Calanus for the prey field cod larvae experience during the period of first feeding.…”

Section: Discussionmentioning

confidence: 97%

“…The Norkyst800 model has shown relatively good agreements with measured currents and hydrography along the Norwegian coast, on the continental shelf and in fjords in several recent studies (Vikebø et al ., ; Asplin et al ., ; Myksvoll et al ., ; Espeland et al ., ; Skarðhamar et al ., ). Our estimate of 2.05 Sv (Fig.…”

Section: Discussionmentioning

confidence: 99%

Mechanisms regulating inter‐annual variability in zooplankton advection over the Lofoten shelf, implications for cod larvae survival

Espinasse

Tverberg

Basedow

et al. 2016

Fisheries Oceanography

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Variability in the availability of suitable prey (mainly nauplii stages of Calanus spp.) in the early life stages of cod is likely a significant contributor to the fluctuations in the year‐class strength in the Arcto Norwegian cod stock. We have investigated the origin of the Lofoten shelf population of Calanus using a particle tracking model approach based on velocity fields simulated from 2002 to 2012. By performing backwards simulations of trajectories from particles released on the Lofoten shelf in early spring, we assessed the relative contribution of potential Calanus sources, such as the Lofoten Basin, the local overwintering on the continental shelf and the adjacent fjords. This analysis revealed significant interannual differences in advection patterns mainly driven by changes in wind conditions and variable strength of the Norwegian Coastal Current. Most of the particles advected into our study area originated on the shelf, and contrary to expectations, only a few originated from the Lofoten Basin where Calanus abundances tend to be high. These results suggest that contribution from the Lofoten Basin to the early spring shelf Calanus population may be overestimated and that contribution from more local sources, especially from adjacent fjords, may play a more important role than what has been previously anticipated. Our results highlight the necessity to improve quantification of shelf‐fjord exchange processes, as these may contribute more to the regulation of spring zooplankton stocks on the northern Norwegian shelf, and, as a result, may affect the survival of cod larvae in this area.

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“…Tides were added to the boundaries of the 800 m model and interpolated from the global TPXO7.2 (Egbert & Erofeeva 2002). Applications eval uating and using 160 m model systems are described by Espeland et al (2015) and Huserbråten et al (2018). The 800, 160 and 32 m models applied high-resolution atmospheric forcing from the nonhydrostatic 2.5 km AROME MetCoOp regional atmospheric model (Müller et al 2017) provided by the Norwegian Meteorological Institute and accessible at http://thredds.met.no.…”

Section: Hydrographic Conditionsmentioning

confidence: 99%

Impacts of salmon lice on mortality, marine migration distance and premature return in sea trout

Llinares

Bøhn

Karlsen

et al. 2020

Mar. Ecol. Prog. Ser.

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Brown trout Salmo trutta (L.) is a facultative anadromous species, where a portion of individuals in populations with access to the sea perform migrations to use the richer feeding resources. We investigated the effect of salmon lice Lepeophtheirus salmonis (Krøyer 1837) infestation on the survival and behaviour of wild trout post-smolts (average fork length = 180 mm) during their marine migration. Comparisons of the marine migratory behaviour were made between an artificially infested group (n = 74) and a control group (n = 71) in an area with low natural lice infestation pressure. Artificial infestation was estimated to cause 100% prevalence and a mean intensity of 65 lice fish-1 (mean relative intensity of 2.4 lice g-1 fish). Survival analysis showed limited statistical power but revealed lice-induced mortality, with an estimated hazard ratio of 2.73 (95% CI = 1.04-7.13) compared to the control group, when data from a previous pilot study were included. Surviving individuals in the infested group additionally responded by residing closer to fresh water while at sea, and by prematurely returning to fresh water. On average, infested fish returned to fresh water after only 18 d at sea, while control fish spent on average 100 d at sea. The residency in the inner part of the fjord and the premature return to fresh water represent an adaptive behavioural response to survive the infestation, at the probable cost of reduced growth opportunities and compromised future fitness.

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Modelling drift of pelagic offspring: the importance of egg surveys in providing a realistic model initialization

Cited by 12 publications

References 38 publications

Coincident Mass Occurrence of Gelatinous Zooplankton in Northern Norway

Coincident Mass Occurrence of Gelatinous Zooplankton in Northern Norway

Mechanisms regulating inter‐annual variability in zooplankton advection over the Lofoten shelf, implications for cod larvae survival

Impacts of salmon lice on mortality, marine migration distance and premature return in sea trout

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