La répartition horizontale et verticale des larves de homard (Homarus americanus) autour des îles de la Madeleine, golfe du Saint-Laurent

1986 ◽  
Vol 43 (11) ◽  
pp. 2164-2176 ◽  
Author(s):  
Christiane Hudon ◽  
Pierre Fradette ◽  
Pierre Legendre
Keyword(s):  
Vertical Distribution ◽  
General Pattern ◽  
Stage Iv ◽  
Homarus Americanus ◽  
Stage I ◽  
Larval Abundance ◽  
Larval Stages ◽  
Vertical Distributions ◽  
Horizontal And Vertical Distributions ◽  
La Madeleine

Thirty-nine stations localized around the eastern tip of the Îles de la Madeleine, in two lagoons, and in the baie de Plaisance were sampled using plankton net tows during the summers of 1978, 1980, and 1981. The horizontal and vertical distributions of each of the four larval stages of Homarus americanus were assessed from sets of surface tows using simple neuston and meter nets (1978 and 1980) as well as a three-compartment plankton net (1981). Most of the stage I larval production takes place in the northeast and southeast regions. However, the abundance of stage IV larvae is low in the southeast and almost nil in the northeast. By contrast, the baie de Plaisance harbors very few stage I larvae, but a very high proportion of stage III and IV larvae. The periods of first appearance and maximum abundance are also out of phase for the three regions, occurring in the northeast before the southeast and the baie de Plaisance. These results suggest that the general pattern of abundance of larvae is driven by the current regime, flushing the larvae around the Pointe de l'Est and concentrating them in the baie de Plaisance following a gyre. On a smaller scale, 12 stations arranged in a 3 × 4 grid in the baie de Plaisance were sampled for 12 wk in the summer of 1980. The first three larval stages show a strongly aggregated distribution and are most frequent at the mouth of the bay. Conversely, stage IV larvae are found more frequently in the shore stations and inside the bay. There is a significant correlation between stage IV larval abundance and the distance to rocky bottoms favorable to benthic life. The vertical distribution of larvae at two stations (1981) shows that only the stage I larvae have a vertical distribution related to light intensity, being found in highest abundance in the surface layer (0–0.8 m) at dusk and dawn. Stage I larvae were uniformly distributed between 0 and 1.6 m during the day and down to 2.4 m at night. Stage II, III, and IV larvae were always found near the surface.

Fickian Transport and the Dispersal of Fish Larvae in Estuaries

1982 ◽  
Vol 39 (8) ◽  
pp. 1150-1163 ◽  
Author(s):  
L. Fortier ◽  
W. C. Leggett
Keyword(s):  
Vertical Distribution ◽  
Fish Larvae ◽  
Sampling Period ◽  
Clupea Harengus ◽  
Tidal Mixing ◽  
Larval Abundance ◽  
Lawrence Estuary ◽  
Larval Stages ◽  
Diel Vertical Migrations ◽  
Average Size

We studied the regulation of ichthyoplankton dispersion in the two-layer circulation of the St. Lawrence upper estuary by determining larval abundance and vertical distribution during high frequency sampling at three stations in May, June, and July, 1979. Monthly variations in capelin (Mallotus villosus) and Atlantic herring (Clupea harengus harengus) abundance were in agreement with the seasonal trends previously reported. Capelin larvae were concentrated in the surface layer, a situation which resulted in seaward drift. No significant growth was observed over the 60-d sampling period indicating continuous recruitment to, and removal from, the sampling area. Herring larvae were concentrated in the deep layer and were carried landward. The average size of herring larvae increased from the downstream to the upstream stations. Short-term fluctuations in the abundance and vertical distribution of the two species were interpreted in terms of the Fickian representation of transport for partially mixed estuaries. The major source of variation in abundance, at a given station, was the tidal advection of horizontal gradients. Capelin larvae and herring larvae smaller than 10 mm did not actively cross the pycnocline and were not submitted to the diffusive effect of the vertical current shear. The dispersal of these larvae was apparently passive. Herring larvae larger than 10 mm performed diel vertical migrations across the pycnocline and were dispersed in the horizontal plane at a faster rate than a passive contaminant of the environment. We conclude that the Fickian approach can be profitably applied to studies of dispersal and mortality of early larval stages of fish in estuaries.Key words: ichthyoplankton, St. Lawrence estuary, dispersion, transport, vertical distribution, diel migrations, variability, abundance, tidal mixing, Fickian

Ecology and Growth of Postlarval and Juvenile Lobster, Homarus americanus, off Îles de la Madeleine (Quebec)

1987 ◽  
Vol 44 (11) ◽  
pp. 1855-1869 ◽  
Author(s):  
Christiane Hudon
Keyword(s):  
Growth Factor ◽  
Size Structure ◽  
Stage Iv ◽  
High Growth ◽  
Homarus Americanus ◽  
Fine Tuning ◽  
Mean Size ◽  
Density And Biomass ◽  
Rocky Bottoms ◽  
La Madeleine

Lobsters, Homarus americanus were studied in various habitats off Îles de la Madeleine, Quebec, from June to October 1985. Density, biomass, and size structure were estimated quantitatively using underwater corrals (40 m2) on rocky bottoms or transects (200 m2) on sandy bottoms and eelgrass beds. On the basis of behavioural observations during capture, lobsters were divided into postlarvae (<25 mm carapace length, CL), juveniles (25–76 mm CL), and adults (>76 mm CL). Density, biomass, and size structure were closely related to the coarseness of the bottom. Density and biomass were greater and mean size was larger on algae-covered boulders than on bare stones. Postlarval and juvenile lobsters were most numerous on shallow rocky bottoms where high densities (0.8–3.8 ind∙m−2) of small lobsters (mean size from 23.8 to 35.5 mm CL) were captured. Low density of juveniles and adults occurred on sand covered with eelgrass. No resident lobsters were found on bare sand. Temporal variation of postlarval density was synchronous at the three stations investigated. Postlarval density decreased during the summer until the settlement of planktonic postlarvae in mid-August. Moulting activity occurred throughout the summer, with a peak in early July. Mean size values for stages V–XIV were fitted to the cumulated size distribution and were used to calculate the percent increment for each moult stage (growth factor) and the expected duration of each stage. The 2-mo duration of the stage IV settlement period could result in a size range of 6–21 mm CL (mean size 14.5 mm CL, stage VIII) for a cohort by the end of its first season of benthic growth. The transition from planktonic to benthic life was characterized by a decrease of the growth factor at stage V, which was subsequently compensated at stages VI and VII by high growth factor values. In the first three growth seasons, spring and summer moults exhibit higher growth factor values than fall moults. These seasonal variations result in regular oscillations of the growth factor dampening progressively between stages V and XIV, instead of the smooth decline hypothesized in previous studies. A combination of factors, such as cryptic behaviour, high substrate selectivity, gradual settlement over the late summer months, and variability in growth factor, reflect the very fine tuning of the lobster's early benthic life stages to the constraints of its physical environment.

Swimming Ability of Larval American Lobsters, Homarus americanus, in Flowing Water

1986 ◽  
Vol 43 (11) ◽  
pp. 2177-2183 ◽  
Author(s):  
G. P. Ennis
Keyword(s):  
Stage Iv ◽  
Homarus Americanus ◽  
American Lobster ◽  
Flowing Water ◽  
Swimming Ability ◽  
Flow Rates ◽  
Larval Stages ◽  
Upstream Direction ◽  
Swimming Capacity ◽  
Observation Period

The swimming capacity of American lobster, Homarus americanus, larvae in flowing water was observed in a screened-off portion of a flow tank. At a flow rate of 2 cm∙s−1, stage I–III larvae were swimming for 46–74% of the observations during the first 5 min but this ranged from 0 to 28% toward the end of a 30-min period. At higher flow rates, however, very few of these larvae were able to continue swimming longer than 5 min. Newly molted stage IV larvae displayed substantially improved swimming ability compared with earlier stages. At 2 cm∙s−1, these larvae were swimming for 40–48% of the observations over the 30-min period, although at higher flow rates their capacity to continue swimming was also limited and few were observed swimming longer than 10 min. Older stage IV larvae were more capable swimmers than newly molted stage IV larvae and displayed a capacity to continue swimming over the 30-min observation period at flow rates up to 9 cm∙s−1. In flowing water, the frequency of orientation in the upstream direction for larvae that were swimming was higher than for control larvae. For stage IV larvae especially, this frequency was higher at the higher flow rates. The observations demonstrate the presence of a rheotactic response in all larval stages of the American lobster. The response is relatively weak in stages I–III but strong in stage IV.

scholarly journals Experimental evidence for concentration-dependence and intra-specific variation of movement behaviour in American lobster (Homarus americanus) larvae

2016 ◽  
Author(s):  
Eric J Pedersen ◽  
Ryan R.E. Stanley ◽  
Paul V.R. Snelgrove ◽  
Frederic Guichard
Keyword(s):  
Vertical Distribution ◽  
Substantial Reduction ◽  
Homarus Americanus ◽  
American Lobster ◽  
High Concentration ◽  
Larval Stages ◽  
Larval Behaviour ◽  
Low Concentrations ◽  
Environmental Responses ◽  
Newly Hatched Larvae

Predicting dispersal paths of marine larvae with long pelagic durations, such as American lobster (Homarus americanus), requires understanding the cues to which larvae respond, and how that response reflects changes in larval behaviour. If larvae respond to conspecific presence by varying their movement, this behaviour can bias laboratory estimates of environmental responses. We tested whether larvae actively decreased their local intraspecific density by measuring how the vertical distribution of larvae changed under high versus low concentrations of conspecifics. We observed weak increases in vertical dispersion at higher concentrations in both newly-hatched larvae and in post-larvae, but not in intermediate larval stages. Further, we found that larvae from different mothers consistently differed in vertical distribution, which may indicate maternal effects on dispersal behavior. We also tested for differences in horizontal swimming behaviour in high and low concentrations, by fitting a novel random walk model that allowed us to model both larval interactions and persistent turning behaviours. We showed substantial reduction in diffusive behaviour under high concentration conditions resulting from more frequent turns by each larva, but no evidence for consistent avoidance of conspecifics. Our study is the first to demonstrate concentration-dependent behaviours in lobster larvae.

Behavioral Responses to Changes in Hydrostatic Pressure and Light During Larval Development of the Lobster Homarus americanus

1975 ◽  
Vol 32 (2) ◽  
pp. 271-281 ◽  
Author(s):  
G. P. Ennis
Keyword(s):  
Hydrostatic Pressure ◽  
Stage Iv ◽  
Homarus Americanus ◽  
Stage I ◽  
Upward Movement ◽  
Larval Life ◽  
Downward Movement ◽  
Vertical Movements ◽  
Instantaneous Pressure ◽  
Pressure Changes

Larvae of the lobster Homarus americanus hatched and reared under laboratory conditions in shallow water responded to changes in hydrostatic pressure in a depth-regulatory manner. Responsiveness to instantaneous pressure increments ranging from 1 to 20 psi increased linearly up to 10 psi but varied little at higher pressures. Sensitivity to pressure changes was retained throughout larval life up to and including stage IV (megalopa) but stage III and IV larvae were much less responsive than stage I and II. Stage V (1st juvenile) lobsters were nonresponsive to pressure changes. Larvae were much less responsive (in terms of vertical movements) to changes in light intensity than to changes in pressure, and there were no clear, sustained phototactic or photopathic responses in the vertical plane.In the sea, stage I, II, and III larvae showed limited downward movement when released at the surface and generally upward movement when released below the surface. Newly-molted stage IV larvae generally remained at the surface when released there and swam to the surface when released at the bottom; those 14–15 days after molting also tended to remain at the surface but when released at the bottom they generally remained there and found shelters. Newly-molted stage V juveniles generally remained where they were released, both at the surface and at the bottom, but those 13–15 days after molting when released at the surface generally swam to the bottom and found shelters, and when released at the bottom, remained there.

Wind-Induced Advection of Larval Decapods into Baie de Plaisance (Îles de la Madeleine, Québec)

1993 ◽  
Vol 50 (7) ◽  
pp. 1422-1434 ◽  
Author(s):  
Christiane Hudon ◽  
Pierre Fradette
Keyword(s):  
Spatial Association ◽  
Homarus Americanus ◽  
Horizontal Distribution ◽  
Climatic Conditions ◽  
Larval Abundance ◽  
Larval Stages ◽  
Early Stages ◽  
The North ◽  
Rock Crab ◽  
Wind Events

Abundance and spatial distribution of the larvae of the American lobster (Homarus americanus), the common rock crab (Cancer irroratus), and the toad crab (Hyas spp.), were monitored weekly during the summer of 1980 at a grid of 12 stations located in Baie de Plaisance. Following a period of winds ≥ 30 km∙h−1 shifting from the north to the southeast, large numbers of late-stage larvae of the three species were advected in the bay, concurrently with an intrusion of low-salinity water. Weekly abundances of consecutive larval stages were highly correlated, indicating that larvae tended to remain in the same water mass. Spatial association tended to be highest among the early stages within each species. The late larval stages of both lobster and rock crab behaved differently from the early stages with respect to light intensity and their horizontal distribution. Although the advection of water masses under the influence of wind events determines the overall abundance of larval decapods in Baie de Plaisance, larval behaviour (vertical migration and swimming ability) also affected distribution of older stage larvae but at a smaller scale. The dependence of advection on sporadic wind events occurring at the time of peak larval abundance reduces the chances of modelling yearly recruitment using average summer climatic conditions.

Abundance, Survival, and Vertical and Diurnal Distribution of Lobster Larvae in Northumberland Strait, 1962–63, and their Relationships with Commercial Stocks

1973 ◽  
Vol 30 (12) ◽  
pp. 1819-1824 ◽  
Author(s):  
D. J. Scarratt
Keyword(s):  
Stage Iv ◽  
Homarus Americanus ◽  
Accurate Prediction ◽  
Larval Abundance ◽  
Sampling Errors ◽  
Diurnal Distribution ◽  
Diurnal Fluctuations

Estimates of the abundance of the four planktonic stages of lobster larvae (Homarus americanus) taken in a large surface plankton net show that production and survival of larvae in Northumberland Strait in 1962 and 1963 were the lowest on record. Examination of diurnal fluctuations in abundance, and sampling below the surface and at various depths to the bottom, confirm that larvae are concentrated at the surface during daylight hours. The time to next molt of stage IV larvae, captured and retained alive, indicates that settlement takes place about midway through stage IV. Reexamination of earlier results together with these new data now suggests there is some evidence for a relationship between stage IV larval abundance and subsequent commercial lobster stocks, but that sampling errors are too great to permit accurate prediction.

Fecundity and release of young in Diastylis sculpta Sars (Crustacea, Cumacea)

1976 ◽  
Vol 54 (11) ◽  
pp. 1946-1949 ◽  
Author(s):  
Susan Corey
Keyword(s):  
Stage Iv ◽  
Stage I ◽  
Larval Stages ◽  
Two Generations ◽  
The Mean

Diastylis sculpta has two generations per year. The mean fecundity for the summer and overwintering females was 20.9 and 72.3 respectively. The marsupial larval stages increase in volume from 0.020 mm3, stage I, to 0.162 mm3, stage IV. The duration of release of the entire brood per female averaged 145 h (range 63–206 h). About 2% of the overwintering females produce a second brook.

scholarly journals Larval Development of the European Lobster and How Small Heterochronic Shifts Lead to a More Pronounced Metamorphosis

2015 ◽  
Vol 2015 ◽  
pp. 1-17 ◽  
Author(s):  
Marie A. I. N. Rötzer ◽  
Joachim T. Haug
Keyword(s):  
Larval Stage ◽  
Stage Iv ◽  
Extreme Case ◽  
Homarus Americanus ◽  
Stage Iii ◽  
American Lobster ◽  
Factors Affecting ◽  
European Lobster ◽  
Larval Stages ◽  
Two Factors

We redescribe the larval stages of the European lobster,Homarus gammarus, based on autofluorescence composite imaging. We focus on larval stages (II) to (IV). Compared to the American lobster,Homarus americanus, differences are most apparent in stage (III). This stage appears more mature inH. gammarus; for example, the rostrum is already curved and bears spines, and the appendages are better developed and longer and more differentiated. InH. americanusstage (III) shows a stronger resemblance to stage (II). As a result of the morphology of stage (III), the “metamorphic” moult between stage (III) and stage (IV) inH. gammarusis less drastic than inH. americanus. Metamorphosis is characterised by two criteria. It involves (1) a drastic change in morphology in (2) a short amount of time. It has hence been suggested that a more pronounced metamorphosis evolves by two factors affecting these criteria, namely, (1) the evolution of specialised larval features, which increase the morphological disparity between larva and adult that makes the change of morphology more drastic, and (2) the skipping of entire stages. This means larval forms ancestrally moult over several intermediate forms into the definite adult morphology. Yet, in more derived forms the stages with intermediate morphologies are no longer expressed; highly specialized larvae moult into the adult within a single moult (in the most extreme case) hence bridging the morphologies of larvae and adult in a shorter amount of time. The example of the twoHomarusspecies demonstrates that this explanation is not the only possible one. Additionally, differences of a single larval stage (in this case larval stage (III)) can lead to a more or less metamorphic-appearing ontogenetic sequence.

Abundance and Distribution of Lobster Larvae (Homarus americanus) in Northumberland Strait

1964 ◽  
Vol 21 (4) ◽  
pp. 661-680 ◽  
Author(s):  
D. J. Scarratt
Keyword(s):  
Surface Waters ◽  
Critical Analysis ◽  
Homarus Americanus ◽  
Stage I ◽  
Larval Stages ◽  
Parent Stock ◽  
Abundance And Distribution ◽  
Surface Drift

A method is described for catching the planktonic larval stages of the lobster (Homarus americanus Milne Edwards). Estimates are made of the abundance and distribution of each of the four stages in the surface waters of part of the Northumberland Strait (southern Gulf of St. Lawrence) for the years 1949–61, with a more critical analysis for the year 1961. Both abundance and survival of the larvae vary from year to year, although they do not appear to be related with measured hydrographical conditions. It is suggested that the distribution of stage I larvae reflects the location of the parent stock and that surface drift carries the developing larvae to possible areas of settlement.There is no conclusive relationship between the larvae and the subsequent stock, although a possible relationship between the abundance of stage I larvae and parent stock density is described and briefly discussed.

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