Diel vertical migration: A possible host-finding mechanism in salmon louse (Lepeophtheirus salmonis) copepodids?

1995 ◽  
Vol 52 (4) ◽  
pp. 681-689 ◽  
Author(s):  
Peter Andreas Heuch ◽  
Aengus Parsons ◽  
Karin Boxaspen

The vertical distribution of pelagic nauplii and copepodids of the salmon louse Lepeophtheirus salmonis Krøyer was studied in large enclosures in the sea. Copepodids, which infect salmonid hosts, displayed a distinct diel vertical migration pattern. They gathered near the surface during the day, and spread out into deeper layers at night. Nauplii showed only small differences in depth between night and day. Copepodid distribution seems to be controlled by light intensity; no effect of either salinity or temperature was found. This migration pattern, which is the reverse of that of wild salmonids, may increase the number of parasite–host encounters as hosts will swim through populations of sinking (nighttime) and rising (dawn) parasites every 24 h. Because caged salmon feed at the surface during the day, they are likely to be more exposed to infective copepodids than wild fish.

Author(s):  
Peter Andreas Heuch

The copepod Lepeophtheirus salmonis Krayer (Copepoda: Caligida), the salmon louse, is a parasite of salmonids. The vertical distribution of the infective stage, the copepodid, was studied in salinity gradients with one step increase of 15‰ (154%e> on top of 304‰), 5‰ (25–4‰ on top of 30–4‰) and 2%> (28–4‰ on top of 304‰) in 1-m perspex columns. Copepodid distribution in a linear gradient, where the salinity increased from 154‰ at 0 cm depth to 304‰ at 87–5 cm, was also recorded. Homogeneous 304‰ salinity columns served as the control. In these, the animals gathered in the top section of the water column in response to 1 h of light from above, and spread downwards in response to 4 h of darkness. In columns with a 15‰ step increase in salinity with depth, copepodids aggregated just underneath the discontinuity irrespective of light conditions. In step salinity gradients of 5‰ and 2‰ S, under both light regimes, animals were significantly more numerous in the step sections compared with the control. In the linear gradient, significant numbers of copepodids accumulated at approximately 20‰ salinity when subjected to 1 h of light. In the dark, there were no significant aggregations. Copepodids were found in 15–17–2‰ salinity in all linear gradient experiments.


Author(s):  
Daichi Uehara ◽  
Jun Shoji ◽  
Yuichiro Ochi ◽  
Shuhei Yamaguchi ◽  
Kazumitsu Nakaguchi ◽  
...  

Diel vertical migration of the cutlassfish Trichiurus japonicus larvae were investigated by consecutive 24-h collections at 3-h intervals at a station in the central Seto Inland Sea, Japan in June and September. Only one larva was collected in June 2017, while 224 and 40 larvae were collected in September 2016 and 2017, respectively. Larvae were present only at depths of ≥ 11 m during the day, whereas they were present at depths of 1, 6, 11 and 16 m during the night. Migration was observed in larvae in which swim bladder formation was completed. A similar pattern, namely nocturnal occurrence at shallow depths only of the developed larvae, was observed in another 24-h survey, suggesting that the swim bladder regulates the upward movement of larvae at night.


2019 ◽  
Vol 41 (4) ◽  
pp. 431-447 ◽  
Author(s):  
Sean Nolan ◽  
Stephen M Bollens ◽  
Gretchen Rollwagen-Bollens

Abstract As the frequency and intensity of hypoxic events increase in both fresh and marine waters, understanding the ecological effects of hypoxia becomes more important. The extant literature reports varying effects of hypolimnetic hypoxia on the vertical distribution and diel vertical migration (DVM) of zooplankton, with some but not all taxa reported to avoid hypoxic waters. We studied the vertical distribution and DVM of diverse zooplankton taxa throughout three seasons over 2 years (2014 and 2015) in Lacamas Lake, WA, USA. We observed hypoxia (<2 mg L−1 dissolved oxygen) in the hypolimnion of Lacamas Lake during five of six sampling periods, with zooplankton populations often exhibiting ‘h-metric’ values (defined as the proportion of a zooplankton population residing within hypoxic waters) ranged from 0.14 to 1.00, with an overall mean of h = 0.66. Moreover, we observed a lack of DVM in most zooplankton taxa on most occasions. Our findings indicate both community-level and taxon-specific zooplankton tolerances to hypoxia, although the exact mechanisms at play remain to be fully elucidated. Nevertheless, the common residency in hypoxic waters and the lack of DVM by diverse zooplankton taxa that we observed likely have implications for food web dynamics in Lacamas Lake and other water bodies.


2011 ◽  
Vol 89 (9) ◽  
pp. 796-807 ◽  
Author(s):  
S. Tang ◽  
A.G. Lewis ◽  
M. Sackville ◽  
L. Nendick ◽  
C. DiBacco ◽  
...  

We observed diel vertical migration patterns in juvenile pink salmon ( Oncorhynchus gorbuscha (Walbaum, 1792)) and tested the hypothesis that fish behaviour is altered by exposure to sea lice copepodids. Experiments involved replicated field deployments of a large (9 m) plankton column, which provided a vertical distribution enclosure under natural light and salinity conditions. Diel vertical distributions of juvenile pink salmon were observed during the first 3 weeks of seawater acclimation in both the presence and the absence of the ectoparasitic salmon louse ( Lepeophtheirus salmonis (Krøyer, 1838)). Immediately upon entering seawater, juvenile pink salmon preferred the top 1 m of the water column, but they moved significantly deeper down the vertical water column as seawater acclimation time increased. A significant diel migration pattern was observed, which involved a preference for the surface at night-time, compared with daytime. When fish in the column were exposed to L. salmonis copepodids for 3 h, 43%–62% of fish became infected, fish expanded their vertical distribution range, and significant changes in vertical distribution patterns were observed.


2011 ◽  
Vol 59 (3) ◽  
pp. 213-229 ◽  
Author(s):  
Cássia Gôngora Goçalo ◽  
Mario Katsuragawa ◽  
Ilson Carlos Almeida da Silveira

Horizontal and vertical distribution patterns and abundance of larval phosichthyids were investigated from oblique and depth-stratified towns off Southeastern brazilian waters, from São Tomé cape (41ºW.; 22ºS.) to São Sebastião island (45ºW.; 24ºS.). The sampling was performed during two cruises (January/2002 -summer; August/2002 -winter). Overall 538 larvae of Phosichthyidae were collected during summer and 158 in the winter. Three species, Pollichthys mauli, Vinciguerria nimbaria and Ichthyioccoccus sp. occurred in the area, but Ichthyioccoccus sp. was extremely rare represented by only one specimen, caught in the oceanic region during the summer. Geographically, larval were concentrated in the oceanic region, and vertically distributed mainly between the surface and 80 m depth in the summer and winter. Larvae were more abundant during the night, performing a diel vertical migration in the water column. The results suggest that the meandering and eddies of Brazil Current play important role on the transport and distribution patterns of larval phosichthyids over the oceanic and neritic area in the Southeastern Brazil.


2007 ◽  
Vol 64 (5) ◽  
pp. 956-962 ◽  
Author(s):  
Rüdiger Voss ◽  
Jörn O. Schmidt ◽  
Dietrich Schnack

Abstract Voss, R., Schmidt, J. O., and Schnack, D. 2007. Vertical distribution of Baltic sprat larvae: changes in patterns of diel migration? – ICES Journal of Marine Science, 64: 956–962. Ontogenetic and diurnal vertical migration patterns of Baltic sprat larvae were investigated for the periods 1989–1990 and 1998–2002. Comparison of the results led to the hypothesis that the diel vertical migration behaviour of sprat larvae >10 mm has changed. In 1989 and 1990, sprat larvae migrated to the surface at night, whereas they stayed 30–50 m deep by day. From 1998 to 2002, sprat larvae showed no signs of diel vertical migration, remaining in warmer, near-surface water by day and night. This behavioural change coincided with a more general change in the Baltic ecosystem, i.e. an increase in near-surface temperature and a general increase in abundance of the major prey organism (Acartia spp.) of Baltic sprat larvae, with more pronounced aggregation in surface waters.


Author(s):  
J. Ringelberg

Proximate aspects of diel vertical migration in the freshwater and marine environment are compared using data from the literature. Examples of migrations in both environments are presented, from which it is concluded that relative changes in light intensity before sunrise and after sunset are primary causes of migrations. Experiments have shown that photoreactive behaviour is enhanced in the presence of predators but inhibited by shortage of food. These factors are called secondary causal factors. A hierarchy of causal factors is proposed. In lakes fish exudates suffice but in marine biotopes like bays, it is possible that fish have to be actually present for enhancement to take effect. To what extent the presented stimulus-response mechanism holds for mesopelagic animals in oceans is discussed on the basis of vertical distributions of euphausiids.


Author(s):  
F. S. Russell

1. Observations are given on the vertical distribution of adult Calanus finmarchicus in the daytime off Plymouth in July and August, 1931, as a result of collections made simultaneously with the photo-electric measurement of submarine illumination.2. A series of nets, usually six, was towed simultaneously in such a manner that the depth of each net was known approximately.3. The female Calanus in July preferred higher intensities of light than did the females in August; this change was coincident with a change in the Calanus population as shown by size measurements. A similar change in distribution and in population was shown by the males.4. The females in July were living in intensities of 20,000 m.c. and more; but those in August were avoiding such high intensities. The males in July avoided intensities of 40,000 m.c. and over, while in August their upper limit was about 10,000 m.c.


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