Delayed capelin (Mallotus villosus) availability influences predatory behaviour of large gulls on black-legged kittiwakes (Rissa tridactyla), causing a reduction in kittiwake breeding success

2000 ◽  
Vol 78 (9) ◽  
pp. 1588-1596 ◽  
Author(s):  
Melanie Massaro ◽  
John W Chardine ◽  
Ian L Jones ◽  
Gregory J Robertson
Keyword(s):  
Breeding Success ◽  
Larus Argentatus ◽  
Hatching Date ◽  
Mallotus Villosus ◽  
Predatory Behaviour ◽  
Rissa Tridactyla ◽  
Herring Gulls ◽  
Capelin Mallotus Villosus ◽  
The Mean ◽  
The Impact

During 1998 and 1999, the impact of predation by herring gulls (Larus argentatus) and great black-backed gulls (Larus marinus) on breeding success of black-legged kittiwakes (Rissa tridactyla) at Gull Island, Witless Bay, southeastern Newfoundland, was quantified in relation to the timing of the annual arrival of capelin (Mallotus villosus) to spawn. The frequency of predation attempts by large gulls on kittiwakes was compared among three periods: before the mean hatching date for herring gulls, between the mean hatching date for herring gulls and the arrival of the capelin, and following capelin arrival. The frequency varied significantly among the three periods, being highest after gull chicks hatched but before the capelin arrived. The frequency of gull predation was significantly correlated with the percentage of kittiwake eggs and chicks that disappeared each week. We estimated that 43 and 30% of kittiwake eggs and chicks at Gull Island were taken by gulls in 1998 and 1999, respectively. Kittiwakes have been indirectly (through increased predation by gulls) affected by the delayed arrival and lower abundance of capelin in recent years, which underlines the need to understand multispecies interactions when interpreting the effects of human alteration of the marine environment.

Ecosystem changes and the effects on capelin (Mallotus villosus), a major forage species

2001 ◽  
Vol 58 (1) ◽  
pp. 73-85 ◽  
Author(s):  
J E Carscadden ◽  
K T Frank ◽  
W C Leggett
Keyword(s):  
Physical Environment ◽  
Population Biology ◽  
Single Species ◽  
Zooplankton Abundance ◽  
Mallotus Villosus ◽  
Northwest Atlantic ◽  
Commercial Fish ◽  
Commercial Exploitation ◽  
Capelin Mallotus Villosus ◽  
The Impact

Capelin (Mallotus villosus), an important forage and commercial fish in the Northwest Atlantic, has exhibited dramatic changes in its biology during the 1990s, coincident with extreme oceanographic conditions and the collapse of major groundfish stocks. Commercial exploitation has not been a serious factor influencing the population biology of capelin in the area. The overall consumption of capelin has declined as predator stock abundances have changed. Data on plankton are sparse, but there appears to have been a decline in zooplankton abundance during the 1990s, and at the same time, a phytoplankton index increased. The impact of the changes in the physical environment has been the subject of previous studies and these are reviewed. The relative impacts of four factors, commercial exploitation, predation, food availability, and the physical environment, on the changes in capelin biology are discussed in the context of capelin as a single species and in the context of the ecosystem. The overall patterns suggest the existence of a "trophic cascade" within the distributional range of capelin in the Northwest Atlantic during the 1990s primarily driven by declines in major finfish predators.

The effects of ice cover over the colony site on reproductive activities of herring gulls

1985 ◽  
Vol 63 (3) ◽  
pp. 607-611 ◽  
Author(s):  
Ralph D. Morris ◽  
John W. Chardine
Keyword(s):  
Lake Erie ◽  
Hatching Success ◽  
Thick Layer ◽  
Egg Laying ◽  
Larus Argentatus ◽  
Herring Gull ◽  
Herring Gulls ◽  
The Mean ◽  
Colony Site ◽  
Reproductive Activities

The substrate at a herring gull (Larus argentatus) colony on Lake Erie near Port Colborne, Ontario (Lighthouse), was completely covered by a thick layer of ice throughout April and early May 1982. Egg laying normally begins at this location in mid-April. An adjacent herring gull colony (Canada Furnace) was ice free. Herring gull pairs at the Lighthouse colony defended territories on top of the ice but only 3 of about 90 pairs built nests on the ice. Birds neither deserted the colony nor moved within it to ice-free areas as these became available. The mean date of egg laying at the Lighthouse colony in 1982 was about 2 weeks later than in the previous year. At the adjacent Canada Furnace colony, there was no difference in the mean date of egg laying between the 2 years. There were no differences in the distribution of clutch sizes, mean clutch sizes, or hatching success of three-egg clutches laid within ± 1 SD of the mean date of egg laying at either colony in the 2 years. By these measures, the ice-induced delay in breeding chronology of birds at the Lighthouse colony in 1982 did not adversely effect reproductive performance in that year.

Changes in nesting-habitat use of large gulls breeding in Witless Bay, Newfoundland

2001 ◽  
Vol 79 (12) ◽  
pp. 2159-2167 ◽  
Author(s):  
Gregory J Robertson ◽  
David Fifield ◽  
Melanie Massaro ◽  
John W Chardine
Keyword(s):  
Reproductive Output ◽  
Prey Species ◽  
No Reduction ◽  
Breeding Habitat ◽  
Larus Argentatus ◽  
Herring Gull ◽  
Fish Prey ◽  
Oceanodroma Leucorhoa ◽  
Herring Gulls ◽  
Capelin Mallotus Villosus

We counted herring gull (Larus argentatus) and great black-backed gull (Larus marinus) nests in the Witless Bay Seabird Ecological Reserve in southeastern Newfoundland, Canada, in 1999 and 2000 and compared our results with previous nest counts from the 1970s. On Gull Island, herring gull nest numbers were 27.5% (1999) and 30.0% (2000) lower than in 1979. Similarly, on Great Island, by 2000 the numbers of herring gull nests had declined 40.8% from numbers in 1979. Counts of great black-backed gull nests were more variable, but suggest a slight or no reduction since 1979. Numbers of herring gulls nesting in rocky and puffin-slope habitats were much reduced (50–70%), while numbers nesting in meadows and forests have actually increased since the 1970s. Great black-backed gulls showed a similar change in nesting distribution. For herring gulls, these changes in nesting numbers matched differences in reproductive success previously documented in these habitats. We suggest that the decline in gull numbers and the change in breeding-habitat selection were caused by changes in the food availability for gulls. Reduced amounts of fisheries offal and the delayed arrival onshore of capelin (Mallotus villosus), an important fish prey species for gulls, have all likely led to the decline in gull reproductive output. Gulls nesting in meadows and forests may be maintaining adequate reproductive output by focusing on alternative prey, such as adult Leach's storm-petrels (Oceanodroma leucorhoa), rather than scarce refuse and fish.

scholarly journals The impact of the sandeel fishery closure on seabird food consumption, distribution, and productivity in the northwestern North Sea

2008 ◽  
Vol 65 (3) ◽  
pp. 362-381 ◽  
Author(s):  
Francis Daunt ◽  
Sarah Wanless ◽  
Simon P.R. Greenstreet ◽  
Henrik Jensen ◽  
Keith C Hamer ◽  
...  
Keyword(s):  
North Sea ◽  
Breeding Success ◽  
Seabird Species ◽  
Rissa Tridactyla ◽  
The North ◽  
Top Predators ◽  
Before And After ◽  
Beneficial Impact ◽  
The North Sea ◽  
The Impact

In the North Sea, the lesser sandeel (Ammodytes marinus) is the target of an industrial fishery and the principal prey of many top predators. Because of concerns about potential effects on predators, the sandeel fishery off eastern Scotland was closed in 2000, and local sandeel abundance increased subsequently. To examine whether closure benefitted sandeel-dependent seabirds, we compared summer sandeel consumption, at-sea distributions, and breeding success of seven species with fishery removals and abundance of older (1+ group) and young-of-the-year (0 group) sandeels from 1996 to 2003. Breeding success of black-legged kittiwake (Rissa tridactyla), a species that has declined in recent decades, was related to abundance of both 1+ group (the age class targeted by the fishery) and 0 group sandeels. The proportion of 0 group consumed by kittiwakes and proportion of the kittiwake population foraging in the area were linked to 0 group abundance. None of these parameters in the other seabird species were associated with sandeel abundance. Our results suggest that fishery closure can have a beneficial impact on top predators sensitive to variation in abundance of the target species, although environmental conditions before and after closure are also likely to be critically important.

Evidence for the Presence of a Metamorphic Check in Capelin (Mallotus villosus) Otoliths and Implications for Age Determination

1977 ◽  
Vol 34 (11) ◽  
pp. 2008-2014 ◽  
Author(s):  
R. F. J. Bailey ◽  
K. W. Able ◽  
W. C. Leggett
Keyword(s):  
Average Length ◽  
Age Determination ◽  
Length Frequency ◽  
Mallotus Villosus ◽  
The Third ◽  
Capelin Mallotus Villosus ◽  
Mean Size ◽  
The Mean ◽  
Age Verification ◽  
Hyaline Zone

The otolith method of aging capelin (Mallotus villosus) from the estuary and western Gulf of St. Lawrence was validated. Hyaline zones are deposited annually in the late fall and winter and thus can be used in age determination. Back-calculated mean length at the first hyaline zone corresponded well with the average length of capelin larvae collected in November and this zone is interpreted as the first annulus. The mean size at the second hyaline zone corresponded exactly with the length at which capelin undergo a profound metamorphosis. This second hyaline zone, which is laid down in the summer of the 2nd yr, was thus interpreted to be a metamorphic check. The third hyaline zone, deposited at a mean length of 95 mm, which corresponded with the peak in the length frequency distribution (when allowance was made for growth), was interpreted as the second annulus. Analysis of two otolith aging techniques currently used suggests that the "Newfoundland" method misinterprets the metamorphic check as the first annulus, rejecting the true first annulus as a "larval check,” a feature having no biological basis in fact. This results in correct ages, but estimates of lengths at the first annulus are exaggerated. The "Greenland" or "Danish" method may misinterpret the metamorphic check as the second annulus thereby resulting in erroneous ages. Key words: capelin, Mallotus villosus, otoliths, age verification, Gulf of St. Lawrence

scholarly journals Low burrow occupancy and breeding success of burrowing petrels at Gough Island: a consequence of mouse predation

2013 ◽  
Vol 23 (2) ◽  
pp. 113-124 ◽  
Author(s):  
RICHARD J. CUTHBERT ◽  
HENK LOUW ◽  
JEROEN LURLING ◽  
GRAHAM PARKER ◽  
KALINKA REXER-HUBER ◽  
...  
Keyword(s):  
Mus Musculus ◽  
Breeding Success ◽  
House Mice ◽  
Population Declines ◽  
Predatory Behaviour ◽  
Breeding Parameters ◽  
Gough Island ◽  
The Impact ◽  
Detrimental Impact ◽  
Winter Breeding

SummaryThe predatory behaviour of introduced house mice Mus musculus at Gough Island is known to impact on albatross and petrels, resulting in the Tristan Albatross Diomedea dabbenena and Atlantic Petrel Pterodroma incerta being listed as “Critically Endangered” and “Endangered”, respectively. Although predation has been documented for two burrowing petrels and one albatross species, the impact of house mice on other burrowing petrels on Gough Island is unknown. We report burrow occupancy and breeding success of Atlantic Petrels, Soft-plumaged Petrels Pterodroma mollis, Broad-billed Prions Pachyptila vittata, Grey Petrels Procellaria cinerea and Great Shearwaters Puffinus gravis. With the exception of the Great Shearwater, breeding parameters of burrowing petrels at Gough Island were very poor, with low burrow occupancy (range 4–42%) and low breeding success (0–44%) for four species, and high rates of chick mortality in Atlantic Petrel burrows. Breeding success decreased with mass, suggesting that smaller species are hardest hit, and winter-breeding species had lower breeding success than summer breeders. The results indicate that introduced house mice are having a detrimental impact on a wider range of species than previously recorded and are likely to be causing population declines among most burrowing petrels on Gough Island. The very low values of burrow occupancy recorded for Soft-plumaged Petrels and Broad-billed Prions and greatly reduced abundance of burrowing petrels in comparison to earlier decades indicate that Gough Island’s formerly abundant petrel populations are greatly threatened by the impact of predatory house mice which can only be halted by the eradication of this species from the island.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Sound Production Treatment for Acquired Apraxia of Speech: An Examination of Dosage in Relation to Probe Performance

2020 ◽  
pp. 1-16
Author(s):  
Julie L. Wambaugh ◽  
Lydia Kallhoff ◽  
Christina Nessler
Keyword(s):  
Retrospective Analysis ◽  
Sound Production ◽  
Apraxia Of Speech ◽  
Practice Schedule ◽  
Practice Schedules ◽  
Baseline Performance ◽  
The Mean ◽  
Number Of Treatment ◽  
The Impact

Purpose This study was designed to examine the association of dosage and effects of Sound Production Treatment (SPT) for acquired apraxia of speech. Method Treatment logs and probe data from 20 speakers with apraxia of speech and aphasia were submitted to a retrospective analysis. The number of treatment sessions and teaching episodes was examined relative to (a) change in articulation accuracy above baseline performance, (b) mastery of production, and (c) maintenance. The impact of practice schedule (SPT-Blocked vs. SPT-Random) was also examined. Results The average number of treatment sessions conducted prior to change was 5.4 for SPT-Blocked and 3.9 for SPT-Random. The mean number of teaching episodes preceding change was 334 for SPT-Blocked and 179 for SPT-Random. Mastery occurred within an average of 13.7 sessions (1,252 teaching episodes) and 12.4 sessions (1,082 teaching episodes) for SPT-Blocked and SPT-Random, respectively. Comparisons of dosage metric values across practice schedules did not reveal substantial differences. Significant negative correlations were found between follow-up probe performance and the dosage metrics. Conclusions Only a few treatment sessions were needed to achieve initial positive changes in articulation, with mastery occurring within 12–14 sessions for the majority of participants. Earlier occurrence of change or mastery was associated with better follow-up performance. Supplemental Material https://doi.org/10.23641/asha.12592190

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