Effect of the Outflow from the Gulf of St. Lawrence on Nova Scotia Shelf Zooplankton

1992 ◽  
Vol 49 (5) ◽  
pp. 857-869 ◽  
Author(s):  
D. D. Sameoto ◽  
A. W. Herman
Keyword(s):  
Nova Scotia ◽  
Surface Water ◽  
Large Population ◽  
Early Spring ◽  
Zooplankton Biomass ◽  
Shelf Break ◽  
Late Winter ◽  
Scotian Shelf ◽  
Calanus Glacialis

Significant differences in concentrations (per square metre) of the copepods Calanus glacialis and C. hyperboreus found between the northeastern (NE) and southwestern (SW) halves of the Scotian Shelf were apparently related to the Gulf of St. Lawrence outflow. This outflow introduces these species to the Shelf during late winter and early spring and is probably responsible for maintaining their populations on the Shelf. Deep basins on the NE half of the Shelf are also sources of breeding animals of these two species. The influence of the Gulf outflow on C. finmarchicus was less clear because a large population of this species was found in the basins and beyond the Shelf break. Temora was the only other copepod genus to show a relationship with the Gulf outflow, indicating that it is carried onto the Shelf from the Gulf. The outflow dominated the surface water of the NE Shelf over the entire year; its influence was less marked on the SW Shelf due to mixing with slope water. This mixing in turn dilutes the concentrations of the Gulf Calanus spp. introduced by the Nova Scotia Current. The Gulf outflow is responsible for the high zooplankton biomass concentrations on the NE Shelf in June and October.

On the Biology and Fishery of the Canadian Atlantic Halibut, Hippoglossus hippoglossus L.

1958 ◽  
Vol 15 (6) ◽  
pp. 1269-1311 ◽  
Author(s):  
F. D. McCracken
Keyword(s):  
Nova Scotia ◽  
Deep Water ◽  
Early Spring ◽  
Large Female ◽  
Late Winter ◽  
Atlantic Halibut ◽  
Large Numbers ◽  
Water Edge ◽  
Mature Fish

Exploratory fishing in the northern Gulf of St. Lawrence in 1945 and 1946 and off western Nova Scotia in 1947 caught 739 halibut, of which 229 were tagged and released. About 590 fish from the commercial fishery of the two regions were also examined.Larger, older halibut were caught in the northern part of the Gulf of St. Lawrence than off western Nova Scotia. Tagged halibut recaptures, size and age composition of commercial landings, and differences in rate of growth suggest generally separate stocks in the two regions.Younger, immature halibut were most available in shallower water; larger, mature fish usually in deep water. Most halibut were caught at temperatures between about 3° and 9 °C. Seasonal, inshore, relatively shallow water halibut fisheries in the northern part of the Gulf of St. Lawrence and off western Nova Scotia occur as the bottom water warms. Large female halibut predominate in such catches.Mature halibut, about 9 to 11 years and older, must spawn in late winter and early spring, probably along the deep-water edge of the banks. Mature halibut grow slowly though the females exceed the mature males and reach a much larger size. The faster-growing, immature halibut of both sexes grow at about the same rate.Halibut landings from ICNAF Subareas 3 and 4 which were at a low level between 1940 to 1948 increased sharply to about 13 million pounds in 1950. More recent landings approximate the long-term annual average of about 5 million pounds. Changes in the level of landings are related to changes in the magnitude of the Canadian fishery which, since 1940, has produced most of the halibut from Subareas 3 and 4.Offshore and inshore fisheries specifically for large halibut produce most of the landings. Catches of halibut taken incidentally in other fisheries contribute little by weight but take large numbers of small, faster-growing individuals. With a continuation of present fishing practices and intensities an annual yield of about 5 million pounds may be expected to continue, but some increased yield might result from controlling the incidental catches of younger halibut. Ways and means of effecting such control should be explored.

Life cycles of four species of Pseudocalanus in Nova Scotia

1989 ◽  
Vol 67 (3) ◽  
pp. 552-558 ◽  
Author(s):  
I. A. McLaren ◽  
Estelle Laberge ◽  
C. J. Corkett ◽  
J.-M. Sévigny
Keyword(s):  
Life Cycle ◽  
Nova Scotia ◽  
First Generation ◽  
Early Summer ◽  
Life Cycles ◽  
The Arctic ◽  
Late Winter ◽  
Early Winter ◽  
Temperature Dependent ◽  
Scotian Shelf

The primarily arctic Pseudocalanus acuspes, relict in Bedford Basin, Nova Scotia, produces a first generation (G1) in late winter; most G1 individuals mature in late spring. The G1 then produces a G2, most of which "rest" in copepodite stages III and IV until early winter. These stages store large amounts of lipid in early summer, which slowly diminish subsequently. A small number of G2 individuals continue to develop at temperature-dependent rates, maturing in early autumn and producing G3 adults in November. Copepodites developing in winter and spring store less lipid. The primarily arctic Pseudocalanus minutus, rare in Bedford Basin and on the Scotia Shelf, is strictly annual, developing to a lipid-filled copepodite stage V after spawning in late winter. The arctic–temperate Pseudocalanus newmani is abundant on the Scotian Shelf, but may not be self-sustaining when advected into Bedford Basin. It stores little lipid and appears to have at least three mature generations at temperature-dependent intervals over Browns Bank between May and November. It may rest in winter, or its life-cycle synchrony by spring could result from food-limited development during winter. The temperate Pseudocalanus moultoni appears to have a life cycle similar to that of P. newmani, but was less common during summer on Browns Bank. These life cycles are appropriately adapted to the geographical ranges of the species, and show some parallels with species of Calanus.

Distribution of Calanus spp. on and around the Nova Scotia Shelf in April: evidence for an offshore source of Calanus finmarchicus to the central and western regions

1999 ◽  
Vol 56 (12) ◽  
pp. 2463-2476 ◽  
Author(s):  
Erica JH Head ◽  
Leslie R Harris ◽  
Brian Petrie
Keyword(s):  
Nova Scotia ◽  
Deep Water ◽  
Shelf Break ◽  
Calanus Finmarchicus ◽  
Surface Layers ◽  
Scotian Shelf ◽  
Near Surface ◽  
Calanus Hyperboreus

Observations of hydrography and Calanus spp. abundance were made at stations on lines across the central and eastern Scotian Shelf (SS) in April 1995 and 1997 and on additional lines on the western SS and across Cabot Strait (CS) and the Laurentian Channel (LC) in 1997. Calanus finmarchicus was more abundant on the central and western SS than in the east, and Calanus hyperboreus was concentrated in the east and in areas influenced by the Nova Scotia Current. Calanus spp. on the eastern SS probably originated mainly from populations overwintering in the Gulf of St. Lawrence. High abundances of C. finmarchicus occurred at or beyond the shelf break when warm slope water was present, suggesting that they derived from a population overwintering in the deep water south of the SS. In both years, slope water was present in the near-surface layers at shelf stations of the Halifax Line (HL), but in 1997 the degree of intrusion was greater. Calanus finmarchicus abundances were also substantially higher at shelf stations of the HL in 1997, implying contribution from the offshore population to the populations in central and western SS regions. Consistent with the suggested difference in their origins, C. finmarchicus on the western SS belonged primarily to the new year's generation, whereas those on the eastern SS belonged mainly to that of the previous year.

Nutrient and plankton distribution near a shelf break front in the region of the Bass Strait cascade

1991 ◽  
Vol 42 (2) ◽  
pp. 201 ◽  
Author(s):  
CF Gibbs ◽  
GH Arnott ◽  
AR Longmore ◽  
JW Marchant
Keyword(s):  
Chlorophyll A ◽  
Dry Weight ◽  
Zooplankton Biomass ◽  
Shelf Break ◽  
Late Winter ◽  
Photic Zone ◽  
North East ◽  
The North ◽  
Tasman Sea ◽  
Plankton Distribution

Nutrient enrichment of surface water to the east of a shelf break front at the eastern end of Bass Strait occurs in winter. This area of enrichment is more than 100 nautical miles (E-W) by 150 nm (N-S). From east of Banks Strait (40� 45'S,148�E), some of the nutrient-rich water is carried northwards with the northward flow of Bass Strait water which later forms the well-known 'cascade' below the warmer waters of the Tasman Sea. In September 1984, the chlorophyll a concentration increased along the line of this northward flow, producing a maximum off the Victorian coast near where the cascade occurs. In contrast to nutrient and chlorophyll a distributions, zooplankton biomass (dry weight) was higher in the shallow water of Bass Strait than over the continental slope. This suggests that the plankton growth observed in shallow Bass Strait waters in late winter had ceased by September, but was continuing to the north-east and over the slope in waters with a shallow mixed depth. We propose that the northward flow of water along the shelf break maintains plankton in a nutrient-rich environment, so that they continue to grow until they are carried below the photic zone by the cascade.

scholarly journals EARLY SPRING FLOWERING IN NOVA SCOTIA: AN EXTREME SPRING IS REFLECTED IN ADVANCED FLOWERING

2013 ◽  
Vol 47 (2) ◽  
Author(s):  
Nicholas M. Hill ◽  
David J. Garbary
Keyword(s):  
Climate Change ◽  
Nova Scotia ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Flowering Phenology ◽  
Early Spring ◽  
Late Winter ◽  
Climate Conditions ◽  
Precocious Flowering ◽  
Native Group

Twenty species of herbaceous plants and four non-amentiferous shrubs were found in flower in March-April in Nova Scotia during the spring of 2012. Plants were observed primarily in Kings and Antigonish Counties, with several observations from Inverness County. The precocious flowering is attributed to an abnormally warm late winter and spring (February-March) in which climate normals for monthly average temperature were exceeded by a minimum of 1.2°C in February (Tracadie) to a maximum of 8.5°C in March (Kentville). Flowering was an average of 17 days earlier than herbarium records in the largest regional herbaria (ACAD, NSAC). Proportional contribution to the early flowering guild was greater for exotic species which featured weedy families not represented in the native group. These observations of spring climate conditions and flowering phenology are consistent with regional climate change associated with milder and earlier springs.Key Words: climate change, Nova Scotia, phenology, spring flowering, exotic range expansion.

Seasonal activity and estivation of lumbricid earthworms in the midlands of Tasmania

Soil Research ◽  
1994 ◽  
Vol 32 (6) ◽  
pp. 1355 ◽  
Author(s):  
RB Garnsey
Keyword(s):  
Soil Moisture ◽  
Adult Development ◽  
Survival Rates ◽  
Soil Surface ◽  
Early Spring ◽  
Lumbricus Rubellus ◽  
Late Winter ◽  
Cocoon Production ◽  
Density And Biomass ◽  
Earthworm Activity

Earthworms have the ability to alleviate many soil degradational problems in Australia. An attempt to optimize this resource requires fundamental understanding of earthworm ecology. This study reports the seasonal changes in earthworm populations in the Midlands of Tasmania (<600 mm rainfall p.a.), and examines, for the first time in Australia, the behaviour and survival rates of aestivating earthworms. Earthworms were sampled from 14 permanent pastures in the Midlands from May 1992 to February 1994. Earthworm activity was significantly correlated with soil moisture; maximum earthworm activity in the surface soil was evident during the wetter months of winter and early spring, followed by aestivation in the surface and subsoils during the drier summer months. The two most abundant earthworm species found in the Midlands were Aporrectodea caliginosa (maximum of 174.8 m-2 or 55.06 g m-2) and A. trapezoides (86 m-2 or 52.03 g m-2), with low numbers of Octolasion cyaneum, Lumbricus rubellus and A. rosea. The phenology of A. caliginosa relating to rainfall contrasted with that of A. trapezoides in this study. A caliginosa was particularly dependent upon rainfall in the Midlands: population density, cocoon production and adult development of A. caliginosa were reduced as rainfall reduced from 600 to 425 mm p.a. In contrast, the density and biomass of A. trapezoides were unaffected by rainfall over the same range: cocoon production and adult development continued regardless of rainfall. The depth of earthworm aestivation during the summers of 1992-94 was similar in each year. Most individuals were in aestivation at a depth of 150-200 mm, regardless of species, soil moisture or texture. Smaller aestivating individuals were located nearer the soil surface, as was shown by an increase in mean mass of aestivating individuals with depth. There was a high mortality associated with summer aestivation of up to 60% for juvenile, and 63% for adult earthworms in 1993 in the Midlands. Cocoons did not survive during the summers of 1992 or 1994, but were recovered in 1993, possibly due to the influence of rainfall during late winter and early spring.

Behaviour and Vocalizations of Two Single Sperm Whales, Physeter macrocephalus, Off Nova Scotia

1988 ◽  
Vol 45 (10) ◽  
pp. 1736-1743 ◽  
Author(s):  
Julia Mullins ◽  
Hal Whitehead ◽  
Linda S. Weilgart
Keyword(s):  
Nova Scotia ◽  
Sound Production ◽  
Ocean Floor ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Scotian Shelf ◽  
Male Sperm

During June 1986, two male sperm whales, Physeter macrocephalus, on the Scotian Shelf were tracked by listening for their clicks with a directional hydrophone for periods of 12.5 and 7 h, respectively. Each whale travelled along the edge of the shelf at about 2 kn (3.6 km/h), and one whale, on two occasions at least, dived to the ocean floor. After about 30 min underwater, the whales spent approximately 9 min at the surface breathing. When the whales were visible at the surface, they were silent, except on one occasion when "slow clicking" (mean interclick interval of 4.6 s) was heard from Whale 2. While underwater, most of the sound production consisted of "usual clicks" (mean interclick interval 0.96 and 0.69 s for the two whales) interrupted by frequent short silences (mean durations 21.06 and 27.82 s) and occasional "creaks" (with interclick intervals less than 0.2 s) and "slow clicks." No "codas" (stereotyped patterns of clicks) were heard from these two single whales. These results are consistent with the hypotheses that "usual clicks" and "creaks" are used for echolocation and "codas" for communication.

TEMPERATURE RESISTANCE OF GOLDFISH MAINTAINED UNDER CONTROLLED PHOTOPERIODS

1959 ◽  
Vol 37 (4) ◽  
pp. 419-428 ◽  
Author(s):  
William S. Hoar ◽  
G. Beth Robertson
Keyword(s):  
Temperature Change ◽  
Seasonal Variations ◽  
Rapid Growth ◽  
Endocrine System ◽  
Early Spring ◽  
Late Winter ◽  
Thyroid Activity ◽  
Temperature Resistance ◽  
Sudden Temperature Change

Goldfish maintained under controlled photoperiods for 6 weeks or longer were relatively more resistant to a sudden elevation in temperature when the daily photoperiods had been long (16 hours) and relatively more resistant to sudden chilling when they had been short (8 hours). The magnitude of the effect varied with the season. Thyroid activity was slightly greater in fish maintained under the shorter photoperiods. The longer photoperiods stimulated more rapid growth of ovaries during late winter and early spring. The endocrine system is considered a link in the chain of events regulating seasonal variations in resistance to sudden temperature change.

Leaf spot and dry rot of lettuce caused by Xanthomonas vitians (Brown) Dowson

1963 ◽  
Vol 14 (6) ◽  
pp. 778 ◽  
Author(s):  
DE Harrison
Keyword(s):  
Leaf Spot ◽  
Early Spring ◽  
Late Winter ◽  
Laboratory Studies ◽  
Dry Rot ◽  
Complete Destruction ◽  
Western Victoria ◽  
Valley Area ◽  
North Western

During the late winter and early spring of 1960, and again to a lesser extent in 1961 and 1962, many lettuce crops in the Murray Valley area of north-western Victoria were seriously affected by a disease characterized by blackening, dry rotting, and collapse of the affected leaves. The incidence of disease varied from about 10% up to practically complete destruction of some plantings. A yellow bacterium was consistently isolated from affected plants and proved to be pathogenic to lettuce. Laboratory studies have shown that the organism agrees closely with the recorded description of Xanthomonas vitians (Brown) Dowson, which has not, apparently, been previously studied in Australia.

Insecticide sprays, natural enemy assemblages and predation on Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae)

2014 ◽  
Vol 104 (5) ◽  
pp. 576-585 ◽  
Author(s):  
C. Monzo ◽  
J.A. Qureshi ◽  
P.A. Stansly
Keyword(s):  
Natural Enemy ◽  
Early Spring ◽  
Citrus Greening ◽  
Asian Citrus Psyllid ◽  
Late Winter ◽  
Diaphorina Citri ◽  
Citrus Groves ◽  
Arthropod Fauna ◽  
Predator Exclusion ◽  
Insecticide Sprays

AbstractThe Asian citrus psyllid (ACP), Diaphorina citri Kuwayama is considered a key citrus pest due to its role as vector of ‘huanglongbing’ (HLB) or citrus greening, probably the most economically damaging disease of citrus. Insecticidal control of the vector is still considered a cornerstone of HLB management to prevent infection and to reduce reinoculation of infected trees. The severity of HLB has driven implementation of intensive insecticide programs against ACP with unknown side effects on beneficial arthropod fauna in citrus agroecosystems. We evaluated effects of calendar sprays directed against this pest on natural enemy assemblages and used exclusion to estimate mortality they imposed on ACP populations in citrus groves. Predator exclusion techniques were used on nascent colonies of D. citri in replicated large untreated and sprayed plots of citrus during the four major flushing periods over 2 years. Population of spiders, arboreal ants and ladybeetles were independently assessed. Monthly sprays of recommended insecticides for control of ACP, adversely affected natural enemy populations resulting in reduced predation on ACP immature stages, especially during the critical late winter/early spring flush. Consequently, projected growth rates of the ACP population were greatest where natural enemies had been adversely affected by insecticides. Whereas, this result does not obviate the need for insecticidal control of ACP, it does indicate that even a selective regimen of sprays can impose as yet undetermined costs in terms of reduced biological control of this and probably other citrus pests.

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