Predation of larval benthic invertebrates in St George’s Bay, Nova Scotia

2012 ◽  
Vol 93 (3) ◽  
pp. 591-599 ◽  
Author(s):  
Jessie Short ◽  
Anna Metaxas ◽  
Rémi M. Daigle
Keyword(s):  
Nova Scotia ◽  
Water Column ◽  
Gasterosteus Aculeatus ◽  
Larval Mortality ◽  
Larval Survival ◽  
Gut Contents ◽  
Larval Abundance ◽  
Species Dominance ◽  
Merluccius Bilinearis ◽  
Larval Species

Larval survival during planktonic dispersal is crucial to the connectivity among benthic populations. Although predation has been suggested as an important cause of larval mortality, this process has rarely been quantified in the field. We measured the abundance of various larval species in the water column in St George’s Bay, Nova Scotia, Canada, on 3 different occasions in summer (August 2008, July and August 2009), the period of high larval abundance in our region. We sampled four numerically dominant predators (scyphozoans: Cyanea capillata and Aurelia aurita; fishes: Gasterosteus aculeatus and Merluccius bilinearis) and lobster larvae near the water surface with a neuston net and other larval species in the water column (3 m depth) with a ring net. Larvae found in the gut contents of the predators included various species of gastropods, crustaceans and bivalves, and these were more abundant in the scyphozoans than the fishes. We attribute these differences to variation in predation method. For certain larval taxa, we found significant differences between the proportional abundance in the guts of C. capillata and in the water column, indicating prey selectivity. This study evaluates the potential impact of predation on larval survival and indicates that the presence of predators can cause changes in abundance and consequent taxonomic shifts in species dominance of larvae, influencing their successful subsequent recruitment to the benthos.

Survival and Abundance of Young Atlantic Cod (Gadus morhua) and Haddock (Melanogrammus aeglefinus) as Indicators of Year-class Strength

1989 ◽  
Vol 46 (S1) ◽  
pp. s171-s182 ◽  
Author(s):  
Steven E. Campana ◽  
Kenneth T. Frank ◽  
Peter C. F. Hurley ◽  
Peter A. Koeller ◽  
Fred H. Page ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Larval Mortality ◽  
Larval Growth ◽  
Melanogrammus Aeglefinus ◽  
Larval Abundance ◽  
Life History Stage ◽  
Spawning Site ◽  
Haddock Melanogrammus Aeglefinus

To identify the life history stage(s) most influential in determining yearclass strength, we constructed and analyzed survival curves of the 1983, 1984, and 1985 cohorts of cod and haddock off Southwest Nova Scotia relative to their physical and biological environment. Relative abundance of each Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) yearclass was not reflected by egg or larval abundance in any year examined. However, abundance of both pelagic and settled juveniles did appear to reflect yearclass strength. Egg and larval mortality could not be consistently linked with advection from the spawning site, and did not covary with subsequent recruitment. In both species, mortality between the larval and juvenile stage was inversely correlated with yearclass strength, but sources of the mortality could not be identified. Larval growth was inversely related to mortality of the early larval stage and independent of larval abundance. However, juvenile growth was proportional to mortality and inversely related to abundance. Despite early life coexistence and similarities in spawning time and location, the relative yearclass strengths of cod and haddock in Southwest Nova Scotia were different, suggesting that the timing of local physical and biological events may play an important role in the recruitment success of these stocks.

scholarly journals Sediment-water column fluxes of carbon, oxygen and nutrients in Bedford Basin, Nova Scotia, inferred from <sup>224</sup>Ra measurements

2013 ◽  
Vol 10 (1) ◽  
pp. 53-66 ◽  
Author(s):  
W. J. Burt ◽  
H. Thomas ◽  
K. Fennel ◽  
E. Horne
Keyword(s):  
Organic Matter ◽  
Nova Scotia ◽  
Water Column ◽  
Explicit Knowledge ◽  
Dissolved Inorganic Carbon ◽  
Chemical Constituents ◽  
Water Interface ◽  
Benthic Fluxes ◽  
Pore Waters ◽  
Overlying Water

Abstract. Exchanges between sediment pore waters and the overlying water column play a significant role in the chemical budgets of many important chemical constituents. Direct quantification of such benthic fluxes requires explicit knowledge of the sediment properties and biogeochemistry. Alternatively, changes in water-column properties near the sediment-water interface can be exploited to gain insight into the sediment biogeochemistry and benthic fluxes. Here, we apply a 1-D diffusive mixing model to near-bottom water-column profiles of 224Ra activity in order to yield vertical eddy diffusivities (KZ), based upon which we assess the diffusive exchange of dissolved inorganic carbon (DIC), nutrients and oxygen (O2), across the sediment-water interface in a coastal inlet, Bedford Basin, Nova Scotia, Canada. Numerical model results are consistent with the assumptions regarding a constant, single benthic source of 224Ra, the lack of mixing by advective processes, and a predominantly benthic source and sink of DIC and O2, respectively, with minimal water-column respiration in the deep waters of Bedford Basin. Near-bottom observations of DIC, O2 and nutrients provide flux ratios similar to Redfield values, suggesting that benthic respiration of primarily marine organic matter is the dominant driver. Furthermore, a relative deficit of nitrate in the observed flux ratios indicates that denitrification also plays a role in the oxidation of organic matter, although its occurrence was not strong enough to allow us to detect the corresponding AT fluxes out of the sediment. Finally, comparison with other carbon sources reveal the observed benthic DIC release as a significant contributor to the Bedford Basin carbon system.

scholarly journals A New Look at Cultivar Preference in Hoplocampa testudinea (Hymenoptera: Tenthredinidae) on Apple in the Annapolis Valley of Nova Scotia, Canada

Insects ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 769
Author(s):  
Suzanne Blatt ◽  
Kim Hiltz
Keyword(s):  
Nova Scotia ◽  
Physicochemical Properties ◽  
Larval Survival ◽  
Larval Performance ◽  
Differential Survival ◽  
Eastern Canada ◽  
Weak Evidence ◽  
Important Pest ◽  
Annapolis Valley ◽  
Hoplocampa Testudinea

(1) Background: The European apple sawfly, Hoplocampa testudinea Klug (Hymenoptera: Tenthredinidae), can be an economically important pest in eastern Canada and shows preference for apple cultivars in Nova Scotia, Canada. We hypothesized that this preference could be due to oviposition by female H. testudinea (preference-performance hypothesis) during the bloom period or differential larval survival during development due to fruitlet physicochemical properties. (2) Methods: Fifteen commercial and experimental apple (Malusdomestica Borkh.; Rosaceae) cultivars located at the Kentville Research and Development Centre (Kentville, Nova Scotia) were chosen and examined for H. testudinea oviposition, larval performance during fruitlet development, fruitlet physicochemical properties and damage assessment at harvest from 2016–2019, inclusive. (3) Results: H. testudinea showed significant cultivar preference during oviposition, during development and at harvest, but the ranking of these cultivars was not the same throughout the season. Total impact by H. testudinea was consistent for most cultivars over multiple years of the study. (4) Conclusion: Correlation of oviposition with damage provided weak evidence for the preference-performance hypothesis. We propose that this relationship is weak due to differential survival of larvae during development.

The fisheries management implications of maternal-age-dependent larval survival

2006 ◽  
Vol 63 (10) ◽  
pp. 2249-2258 ◽  
Author(s):  
Michael R O'Farrell ◽  
Louis W Botsford
Keyword(s):  
Mortality Rate ◽  
Fisheries Management ◽  
Maternal Age ◽  
Egg Production ◽  
Larval Mortality ◽  
Reproductive Potential ◽  
Larval Survival ◽  
Age Effects ◽  
Fishing Mortality ◽  
Black Rockfish

A common goal of conventional fisheries management is to maintain fishing mortality at a rate that ensures an adequate level of lifetime egg production (LEP) for population sustainability. However, larvae from young spawners can experience higher mortality rates than larvae of older spawners, reducing the effect of egg production by young females (hereafter, maternal age effects). This reduction leads to an error in LEP that can be accounted for by reducing the fishing mortality rate, but raises the question of the magnitude of these errors if they are present but not accounted for. Calculations using parameters from a typical long-lived fish demonstrated that maternal age effects resulted in large errors in estimates of lifetime reproduction when there was a large contrast in the larval mortality rate extending over the reproductive life span. Errors were small when maternal age effects reduced the reproductive potential of only the very youngest spawners, at ages when a small fraction of females are mature. A specific example using the empirically derived maternal age effect for black rockfish (Sebastes melanops) indicated that errors in traditional management would be small for this species.

Southern king crab larval survival: from intra- and interfemale variations to a fishery-induced mortality

2020 ◽  
Vol 77 (12) ◽  
pp. 1893-1903
Author(s):  
Pablo Di Salvatore ◽  
Hernán J. Sacristán ◽  
M. Paula Sotelano ◽  
Federico Tapella ◽  
María Gowland-Sainz ◽  
...  
Keyword(s):  
Glycogen Content ◽  
Larval Mortality ◽  
Extended Period ◽  
Free Fall ◽  
Larval Survival ◽  
Aerial Exposure ◽  
Hedging Strategy ◽  
Air Exposure ◽  
King Crab ◽  
Energetic Reserves

The southern king crab (Lithodes santolla) supports one of the most important fisheries in southern South America. Lecithotrophic larvae hatch over an extended period, in which brooding females can be fished, but must be discarded due to regulations. Larval mortality by female fishing was evaluated. Samples of newly hatched zoeae I were obtained the day before (control) and after female treatment (aerial exposure or aerial exposure + free fall). Independently of the mothers’ treatment, larvae survived less than those from the control, explained by the air-exposure effects. The intraclutch variability in larval survival and their variability in energetic reserves were studied. Females were maintained during the hatching period, and zoea I samples were taken during 3 successive days. We found high variation in larval survival within a single egg clutch and between different females, only ascribable to the initial larval glycogen content. The intraclutch variability in larval survival combined with extended hatching may be an adaptation that allows mothers to find an adequate substrate as larvae hatch and may constitute a diversified bet-hedging strategy.

scholarly journals Lack of Effects On Bumblebee (Bombus Terrestris) Colony Development And Drone And Queen Production Due To The Insecticide Chlorantraniliprole

2021 ◽  
Author(s):  
Axel Dinter ◽  
Olaf Klein ◽  
Lea Franke
Keyword(s):  
Bombus Terrestris ◽  
Larval Mortality ◽  
Larval Survival ◽  
Flight Activity ◽  
Colony Development ◽  
Growth Stages ◽  
Monitoring Site ◽  
Worst Case ◽  
Set Up ◽  
Spray Applications

Abstract The aim of the study was to investigate the potential impact of the insecticide chlorantraniliprole on queen-right bumblebee (Bombus terrestris) colonies under semi-field conditions in Phacelia tanacetifolia. The P. tanacetifolia crop was grown in soil treated with modelled worst-case 20-year plateau concentration of chlorantraniliprole in the top 20 cm of soil (equivalent to 0.088 mg a.s./kg). Additionally, two chlorantraniliprole spray applications at 60 g a.s./ha were made. In treatment T1 both spray applications took place before P. tanacetifolia flowering at growth stages BBCH 51–55 and BBCH 55–59. In T2 one spray application was conducted before P. tanacetifolia flowering at BBCH 55–59 and one application during P. tanacetifolia flowering and during daily bee flight at BBCH 61–62. The application in the control (C) and reference item treatment (R) (400 g dimethoate a.s./ha) was carried out during full P. tanacetifolia flowering and bumblebee flight. The bumblebee colonies were exposed to the treated flowering P. tanacetifolia crop for 20 days in the tunnels and afterwards the colonies were kept on a monitoring site. Results of this study indicate no significant differences between the chlorantraniliprole groups T1 and T2 and the control regarding all parameters assessed (i.e. adult and larval mortality, flight activity at the hive entrance, colony weight development, condition of the colonies and production of young queens and males). Overall, no effects of chlorantraniliprole on B. terrestris colonies including queen/male production, adult and larval survival, colony development and forager flight activity were found in this worst-case exposure set-up.

Who is Qualified to Survey Canada’s Offshore?

1984 ◽  
Vol 38 (1) ◽  
pp. 15-25
Author(s):  
A. J. Kerr ◽  
P. K. Mukherjee
Keyword(s):  
Nova Scotia ◽  
International Law ◽  
Water Column ◽  
Regulatory Authority ◽  
Law Of The Sea ◽  
Federal Legislation ◽  
Generic Sense ◽  
Hydrographic Surveying

An examination is made of what constitutes offshore survey, who is qualified to carry out such a survey and what is Canada’s offshore in terms of the new international law of the sea. It is submitted that the term “offshore” as used in a generic sense consists of two components, i.e., (1) the seabed and subsoil; and (2) the superjacent water column. It appears that under the Canada Lands Surveys Act the term “survey” is inadequately defined, giving rise to the impression that only persons holding a commission as a Canada Lands Surveyor may survey the offshore in any sense, including hydrographic surveying. It is submitted that the term “hydrographic surveying” when used in a given context, could denote either a methodology, or a purpose or both. It is proposed that more precise definitions are required for the term “survey” in relevant federal legislation and that consideration be given to defining legal surveys in terms of title or ownership as is the case for example, with Nova Scotia legislation. This would make it clear that boundary or delimitation surveys for the purpose of separating jurisdictional units are not regulated under the Canada Lands Surveys Act. This would be consistent with international practice where it has been geographers and hydrographers who have been considered the experts in the field of delimitation of boundaries between maritime jurisdictional units. It is further proposed that all offshore surveys using hydrographic methodology, in particular those carried out for the purpose of defining boundaries of jurisdictional units, be brought under the regulatory authority of the Dominion Hydrographer through appropriate legislation.

scholarly journals Interannual variability of diet composition and prey preference of larval redfish (Sebastes spp.) in the Gulf of St. Lawrence

2020 ◽  
Vol 42 (5) ◽  
pp. 581-594
Author(s):  
Corinne M Burns ◽  
Félix Lauzon ◽  
Stéphane Plourde ◽  
Pascal Sirois ◽  
Dominique Robert
Keyword(s):  
Interannual Variability ◽  
Diet Composition ◽  
Calanoid Copepod ◽  
Fish Larvae ◽  
Larval Survival ◽  
Calanus Finmarchicus ◽  
Gut Contents ◽  
Reproductive Phenology ◽  
Prey Identification ◽  
Sebastes Mentella

Abstract Spatiotemporal overlap between fish larvae and their planktonic prey is an important source of recruitment variability. Over the past decade, one species of redfish, Sebastes mentella, from the Gulf of St. Lawrence (GSL) produced multiple strong cohorts following decades of low recruitment, which has generated strong interest in identifying potential drivers of larval survival. The present study provides the first detailed, multi-year assessment of larval redfish (Sebastes spp.) trophodynamics. Interannual variability in larval redfish diet composition and prey selectivity was assessed using high-resolution prey identification of larval gut contents and in situ prey fields. Eggs from the calanoid copepod Calanus finmarchicus represented the most frequently consumed prey in 3 of the 4 collection years, and contributed the largest proportion of carbon ingested by redfish larvae in all years. The high consumption of C. finmarchicus eggs by larvae, combined with evidence of positive selection for this taxon in some years, supports the hypothesis of a strong trophic link between larval redfish and a key calanoid copepod in the GSL ecosystem. Our results indicate that future efforts investigating GSL redfish recruitment processes should consider environment-driven variability in the reproductive phenology and abundance of C. finmarchicus.

Multiple effects of tebufenozide on the survival and performance of the spruce budworm (Lepidoptera: Tortricidae)

2016 ◽  
Vol 149 (2) ◽  
pp. 227-240 ◽  
Author(s):  
Kees van Frankenhuyzen ◽  
Jacques Régnière
Keyword(s):  
Mating Success ◽  
Choristoneura Fumiferana ◽  
Larval Mortality ◽  
Pupal Stage ◽  
Spruce Budworm ◽  
Larval Survival ◽  
Host Trees ◽  
Population Reduction ◽  
High Larval Mortality ◽  
And Performance

AbstractAerial application of Mimic® 2LV to rising outbreak populations of the spruce budworm (Choristoneura fumiferana (Clemens); Lepidoptera: Tortricidae) in Québec, Canada, resulted in high levels of population reduction at spray deposits of 0.5–1.2 μg tebufenozide/g of foliage. Application to potted host trees in outdoor enclosures followed by bioassays revealed multiple effects on spruce budworm survival and recruitment. Chronic (14-day) exposure of late-instars to treated foliage reduced larval survival and also pupal survival, mating success, and fecundity, depending on the product concentration applied. Treatments that produced foliar deposits of ~ 0.5–1.5 μg tebufenozide/g caused high larval mortality. Exposure to deposits of ~ 0.15–0.5 μg/g caused delayed mortality during the pupal stage and reduced the mating success of survivors, while exposure to ~ 0.07–0.15 μg/g reduced the fecundity of mated females. Sublethal exposure did not affect the progeny of survivors, either in egg hatch, survival during diapause, or survival and performance after diapause. Reduced survival during late-larval and pupal stages combined with lower recruitment as a result of reduced mating success and fecundity are likely to play a role in the suppression of Mimic®-treated spruce budworm populations in the years following treatment.

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