首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Ascophyllum nodosum (rockweed) is the main economic resource of the seaweed industry in the Atlantic Provinces of Canada. The annual harvest steadily increased since 1995, reaching a historic peak of 37,000 tonnes in 2007. Due to a high demand for fertilizers and animal feed supplements derived from rockweed, this trend seems likely to continue. The current management plan for the sustainable harvest of the A. nodosum resource is considered conservative. The resource has been managed with a precautionary approach since 1995 to protect the integrity of the habitat. Acadian Seaplants Limited (ASL) has been granted approximately 90% of the government-issued licenses to harvest A. nodosum resources in the Maritimes. The Canadian approach is based on an annual harvest from a given bed and not strip-and-return after several years. Since 1995, ASL has proactively undertaken extensive annual surveys and research on biomass productivity of this renewable resource to establish acceptable annual exploitation rates. Historically, the rockweed beds of southwestern Nova Scotia (NS) have been almost 99% pure A. nodosum, with a minor component of Fucus vesiculosus. However, since 2004, a steady increase in F. vesiculosus, with a peak of 4.6% of the total biomass in 2008, was recorded. This coincided with one of the mildest winters on record for the Maritimes. This increase in temperature seemed to be also responsible for an unusual recruitment of the blue mussel Mytilus edulis in rockweed beds in some areas of southern New Brunswick (NB) in 2006, causing the detachment of up to 30% of the seaweed biomass in some harvesting sectors. Another phenomenon observed in southwestern NS during 2003 and 2004 was extensive ice damage on rockweed beds produced by an early melting of the ice, with losses of up to 90% of the rockweed biomass in some areas.  相似文献   

2.
Ascophyllum nodosum (rockweed) landings in the Atlantic Maritime provinces of Canada totalled 36,500 wet tonnes in 2009. Due to the relative slow growth, stochastic recruitment, and the importance of habitat protection, strict harvest regulations are in place in the region to maintain the integrity of this resource. Special harvesting rakes have been designed to cut the plants and not to dislodge the clumps and their holdfasts from the substratum. However, for various reasons, close to 6% of the biomass harvested annually contains holdfast material. This proportion is closely monitored by the province as it is assumed to represent clump mortality. However, due to the complex structure of A. nodosum clumps, this relationship with mortality is not simple. A study was carried out to evaluate the real impact of this detachment on the A. nodosum population of southern New Brunswick in 2004. The structure of harvested A. nodosum clumps with associated holdfast material was analyzed and compared to non-harvested clumps from the same harvest area. Results showed that when a rake strips a clump, it only detaches 17.4% of the holdfast surface, leaving 36.8% of the plant biomass and 80.3% of the shoot density intact. An analysis of storm-cast material from the same study area showed a similar effect in the clump structure, although the incidence of holdfast in the detached biomass could be as high as 30%. Due to the high biomass detached each year by coastal storms in New Brunswick, their impact on the A. nodosum resource is 21 times higher than the annual harvest.  相似文献   

3.
Commercial exploitation of Ascophyllum nodosum (rockweed) along the coast of Nova Scotia began in the late 1950s when it was used as a raw material for manufacturing alginate and “kelp” meal. Today, this resource is used as a biostimulant extract for crops and animal feed supplements and is the main economic resource of the seaweed industry in the Maritime Provinces and Canada. The management of rockweed, by dividing the resource into many sectors, permitted the assessment of yield per unit area of bed. In Nova Scotia, mechanical harvesting of A. nodosum operated on a pulse of 2- to 3-year schedule providing yields of 21.9 to 47.7?wet?t ha?1 averaging 35.3?±?7.6?wet?t ha?1. Acadian Seaplants Limited (ASL) has become the dominant player in the region since 1995 with more than 75% of the total biomass under its leases and more than 90% of the total landing of rockweed in the last 13?years. Sustained harvests at ASL leases and under an annual harvest schedule using hand cutting methods have averaged 17.4?±?2.6?t ha?1. Exploitation rates above 35% of the harvestable crop lead to a pulse harvest strategy and the need to move infrastructure year after year. In New Brunswick, a new approach to management began in 1995 with a regulated 17% exploitation rate. Thus, the yield in that province is 14.3?wet?t ha?1. The current summer standing crop for this region has been calculated at 352,723?wet?t, covering an area of 4,960?ha, with an average biomass of 71.3?t ha?1. The harvest in the region reached peak landings in 2010 with just over 40,100?t. The consistent yield per hectare of A. nodosum beds is proof of good management practices and an ecologically sustainable harvest in the Canadian Maritimes.  相似文献   

4.
The maritime shrew, Sorex maritimensis, is a Canadian endemic species with a limited distribution in two provinces in eastern Canada. Phylogeographic analysis of mitochondrial DNA control region and cytochrome b sequences revealed two clades, one found in New Brunswick and the other primarily in Nova Scotia, Canada. We propose that these clades have come back into secondary contact following the Wisconsin glaciation via wetlands on the narrow Isthmus of Chigneto that connects these provinces. Despite evidence of an historic separation of maritime shrew subpopulations in Nova Scotia and New Brunswick, we conclude that shrews in these two regions should be considered a single evolutionary significant unit but separate, semi-isolated management units that should be recognized as such for conservation purposes. The susceptibility of this stenotopic species with limited dispersal capabilities raises concerns about its long-term persistence if climate-change induced habitat fragmentation increases. Maintenance of contiguous wetland habitats is needed to ensure connectivity and gene flow among populations of the maritime shrew.  相似文献   

5.
References Rangeley (1994) has argued that sampling biases, errors in experimental design and low statistical power make the conclusion by Black & Miller (1991), that there was no large impact of an experimental harvest of the seaweedAscophyllum nodosum on fishes, unmerited and misleading. Our study was conducted mainly at two sites close to Lower Argyle, southern Nova Scotia, Canada where harvesting ofAscophyllum nodosum has been carried out continuously for 30 years along-side intense and productive shellfish and finfish fisheries. In southern Nova Scotia, on-going removal ofAscophyllum nodosum with mechanical harvesters is about 17% (Sharpe & Semple 1991); planned annual removal in New Brunswick where Rangeley has worked will be only about 5% (Anon. 1993). The context of our investigation was a small-scale (400 m2) but extreme, experimental removal (100%) of the seaweed. Our focus was on fishes that moved into the intertidal zone as the tide rose in the evening and early morning and were caught in trammel nets, and on the fishes that were retained in a fixed seine that was set at high tide in early morning and the fishes removed at the next low tide. Thus, subject to the constraint on the size of the fishes imposed by the nature of our fishing gear with its stretch mesh of 25 mm, we were concerned with the identity and abundance of fishes that moved in and out of the intertidal zone and their behavioural response to the 400 m2 patches of habitat that formed our experimental units. The most striking result was the unexpected, low abundance of fishes caught in our gear.  相似文献   

6.
Shoots and clumps of shoots of the commercial brown seaweed Ascophyllum nodosum (“rockweed”) add to the benthic complexity of the intertidal environment, providing an important habitat for invertebrates and vertebrates. To protect the structure of this habitat, management plans for the rockweed harvest of southern New Brunswick include restrictions on gear type and exploitation rates limited to 17% of the harvestable biomass. However, owing to physical and environmental factors, the harvest is not homogeneous, creating patches of exploitation ranging from 15 to 50%.A direct relationship existed between clump vulnerability, weight and length in a controlled harvest at 50% exploitation within 8 m by 8 m plots. At this exploitation rate, the gear rarely impacted clumps below 50 g or 60 cm in length. Clumps larger than 300 g and 130 cm were reduced by up to 55% of their length and 78% of their biomass. The overall impacts of the harvest on intertidal habitat is however of short duration as biomass recovers after a year of the experimental harvest. The rapid recovery is mostly due to a stimulation of growth and branching of the suppressed shoots of the clumps. Some harvested plots showed biomass even higher than initial levels, suggesting an increase in productivity at least during the first year after the harvest.  相似文献   

7.
On NW Atlantic rocky shores, the main basal organisms in intertidal communities are seaweeds (Ascophyllum nodosum, Fucus spp. and Chondrus crispus) and filter feeders (barnacles, Semibalanus balanoides, and mussels, Mytilus spp.). Their ecology has been extensively studied in New England (United States), but knowledge gaps exist for northern shores, which are subjected to stronger environmental stress. Therefore, we studied the above organisms on Canadian shores. We quantified the summer abundance of these seaweeds and filter feeders across full vertical (intertidal elevation) and horizontal (wave exposure and winter ice scour) environmental gradients on the Gulf of St. Lawrence and open Atlantic coasts of Nova Scotia. At the regional scale along the open Atlantic coast, seaweeds showed similar abundances in Nova Scotia than values reported for New England. However, both filter feeders were considerably less abundant in Nova Scotia. At the local scale in Nova Scotia, intense winter ice scour (which only occurs on the Gulf of St. Lawrence coast) was associated with a very low abundance of all species except barnacles. Spatial trends in Nova Scotia were similar to patterns known for certain species elsewhere, such as A. nodosum being almost restricted to sheltered habitats, regardless of elevation, and C. crispus being almost restricted to low elevations, regardless of exposure. Other trends were, however, characteristic of Nova Scotia, such as C. crispus being frequent at low elevations in exposed habitats, unlike in New England, where mussels often predominate there because of competitive advantages. In Nova Scotia, mussels were always restricted to cracks and crevices, unlike in New England, where they form extensive intertidal beds on exposed shores. The direct effects of increased environmental stress and indirect effects through altered interspecific interactions might explain the regional differences in local species distribution, which will require experimental validation. Handling editor: K. Martens  相似文献   

8.
Synopsis In Nova Scotia the annual harvest of the intertidal seaweed Ascophyllum nodosum exceeds 20 000 tons. This study investigated the possible impact of removal of the seaweed on intertidal abundance of fishes and their gut contents. At sites near Lower Argyle, Nova Scotia, absolute abundance of fish in small areas with Ascophyllum removed and intact was determined with pop-up seines. Gut contents were investigated from fish collected with the seines and with trammel nets. Number and weight of fish were not significantly different between cleared and intact areas and averaged 4.6 individuals and 160 g per 400 m2 during June to October. Cunner and sculpins had more food in their guts when leaving than when entering the intertidal, but only cunner had more food in their stomachs when leaving intact areas than when leaving cleared areas. Most fish captured in the intertidal were small (< 15 cm) and of no commercial value, and the numbers of commercial species were too low to be of much value. Numbers of fish in the intertidal was significantly lower than in the shallow subtidal. This study provided no evidence for adverse effects of the removal of patches of Ascophyllum on fishes.  相似文献   

9.
We report 63 species of Curculionoidea that are new to New Brunswick (three species of Anthribidae, four species of Brentidae, three species of Dryophthoridae, three species of Brachyceridae, 50 species of Curculionidae). Among these are 27 species (two Anthribidae, two Brenthidae, one Brachyceridae, 22 Curculionidae) that are also newly recorded for the Maritime provinces, and one species, Plesiobaris disjuncta Casey (Curculionidae) that is newly recorded for Canada from New Brunswick and Quebec. Bagous planatus LeConte is reinstated to the faunal list of New Brunswick. Two species of Curculionidae are newly recorded from Nova Scotia and the Maritime provinces, and two others are reported for the first time for Prince Edward Island.  相似文献   

10.
Infectious salmon anaemia (ISA) is a serious disease responsible for high morbidity in farmed Atlantic salmon Salmo salar in Norway, Scotland and New Brunswick, Canada. Recent attempts to identify different strains of ISA virus (ISAV) based on nucleotide sequence variation have shown that the Norwegian and Scottish samples are similar to one another but markedly different from New Brunswick samples. These data may suggest the presence of different strains on each side of the Atlantic but no functional difference has been found with either strain. We describe the first identification and characterisation of ISAV in Atlantic salmon from Nova Scotia, Canada. Further, salmon infected with the Nova Scotia ISAV do not show typical ISAV pathology or mortality. Sequencing of this new strain showed it to possess greater similarity to ISAV from Norway and Scotland than to ISAV from New Brunswick. These findings are discussed in terms of a possible origin of the Nova Scotia ISAV strain and the existence of an avirulent ISAV strain. The impact of current strain variation studies on our knowledge of ISAV is also discussed.  相似文献   

11.
Grynocharis quadrilineata (Melsheimer) and Tenebroides corticalis (Melsheimer) of the family Trogossitidae are newly recorded for New Brunswick, Canada. Additional records of the recently reported Calitys scabra (Thunberg)and Ostoma fraterna (Randall) are presented for the province. The record of Ostoma fraterna is the first recent record of this species from New Brunswick. Additional New Brunswick records of the thaneroclerine, Zenodosus sanguineus (Say), are given, indicting that this species is common and widespread in the province. One species of Cleridae, Cymatodera bicolor (Say),is newly reported from New Brunswick, and the adventive Thanasimus formicarius Linnaeus is newly recorded from Nova Scotia and the Maritime provinces. Attalus morulus (LeConte) and Dolichosoma foveicolle (Kirby), family Melyridae, are reported for the first time for New Brunswick and the Maritime provinces. Collection, habitat data, and distribution maps are presented for these species.  相似文献   

12.
Ang  Put O.  Sharp  Glyn J.  Semple  Robert E. 《Hydrobiologia》1996,326(1):179-184
Changes in the structure of the Ascophyllum nodosum population at Pubnico, southwest Nova Scotia, Canada, at an experimental site subjected to mechanical harvest and at two control sites never subjected to mechanical harvest were monitored from 1991 to 1994. A bimodal population structure measured in terms of plant length was characteristic of all these sites before the experiment. The population structure of the experimental site became unimodal immediately after experimental harvest by machine and remained unimodal for the subsequent two years. However, a bimodal population structure began to appear in the third year. A bimodal population structure remained evident at the control site with bedrock as the substratum but was less evident at the other control site where the substratum is made up of boulders and cobbles. Movement of loose rocks with rockweeds still attached may have contributed to the less distinct modal structure of this control site. Other sites with different harvesting histories monitored in the summer of 1992 showed some interesting patterns. A unimodal population structure was evident in Argyle Sound and Pubnico Point South and at Charlesville, which had been harvested one and two years before, respectively. A bimodal population structure was more evident at Frenchman's Point, which had been harvested three years prior. The rate of change from a unimodal to a bimodal population structure may depend on the intensity of harvest. Extensive canopy removal in intensively harvested areas may be conducive to an influx of recruits and to regeneration from the holdfast. Hence, plant length modal structure may be a useful measure of the relative state of recovery of a harvested population.  相似文献   

13.
Garbary  D.J.  &Jess  C.B. 《Journal of phycology》2000,36(S3):23-24
Ten years after the initial discovery of Codium fragile in eastern Canada on the Atlantic coast of Nova Scotia, C. fragile has extended its range considerably to northern Nova Scotia, southern New Brunswick and Prince Edward Island (P.E.I.) in the Gulf of St. Lawrence. In all principal areas C. fragile subsp. tomentosoides is present. In two regions of Prince Edward Island, Codium is becoming extremely abundant, and is known by local fishers as the "oyster thief". A potential second taxon of Codium was collected in 1999 at three sites in Malpeque Bay where it is locally abundant. These plants are distinguished from C. fragile subsp. tomentosoides by their smaller frond size, flatter utricle tops, smaller mucrons, and smaller gametangia. Principal component analysis distinguishes plants of the two types. The abundance of C. fragile on both hard bottom and soft bottom substrata suggests that it will become the dominant alga in many subtidal algal communities in eastern Canada.  相似文献   

14.
The seaweed Ascophyllum nodosum (Phaeophyceae, Fucales) often forms extensive beds in wave‐sheltered, rocky intertidal habitats on northern Atlantic shores. Since this alga is an ecosystem engineer that influences benthic biodiversity, it is important to understand the factors that regulate its performance. Epiphytism is known to affect the performance of macroalgal hosts. In this study, we investigated the effects of surface irregularities on A. nodosum fronds (wounds, branch axils, and lateral pits resulting from receptacle shedding) on the recruitment rate of its obligate epiphyte Vertebrata lanosa (=Polysiphonia lanosa, Rhodophyta, Ceramiales). For this purpose, we performed a field experiment in Nova Scotia, Canada. In June–July 2007, we created wounds on the surface of host fronds that mimicked the wounds that result from invertebrate grazing. At that time, we also mapped the position of epiphyte‐free lateral pits and branch axils on host fronds. In October 2007, after the reproductive season for V. lanosa, the percentage of microsites colonized by this epiphyte was statistically similar for wounds and lateral pits, but significantly lower for branch axils, although by a small difference (mean recruitment rates ranged between 37 and 50%). Since V. lanosa is known not to colonize smooth frond surfaces, our study suggests that the degree of epiphyte load on A. nodosum beds should largely be affected by the overall amount of surface irregularities, with little influence of the relative availability of each microsite type.  相似文献   

15.
J. A. McKiel 《CMAJ》1964,91(11):573-577
A Canada-wide survey of Q fever was begun in 1958 in co-operation with public health and veterinary laboratories to determine the presence and prevalence of the disease so that medical practitioners might be alerted to the potential dangers existing. Serologic evidence obtained indicated that the Q fever rickettsia now exists in cattle in all provinces of Canada except New Brunswick, Nova Scotia, and Prince Edward Island. Isolations of the rickettsia were obtained from bovine milk samples from Ontario and Quebec. The data suggest that the etiologic agent was not present in the western provinces during the early 1950''s but since having been introduced into that area it has established itself successfully, particularly in Alberta. The ease with which the disease in man may be missed is illustrated by a previously unreported case which occurred in 1960 in the Eastern Townships of Quebec.  相似文献   

16.
Assessing spatial variation in waterfowl harvest probabilities from banding data is challenging because reporting and recovery probabilities have distinct spatial patterns that covary temporally with harvesting regulations, hunter effort, and reporting methods. We analyzed direct band recovery data from American black ducks banded on the Canadian breeding grounds from 1970 through 2010. Data were registered to a 1‐degree grid and analyzed using hierarchical logistic regression models with spatially correlated errors to estimate the annual probabilities of band recovery and the proportion of individuals recovered in Canada. Probability of harvest was estimated from these values, in combination with independent estimates of reporting probabilities in Canada and the USA. Model covariates included estimates of hunting effort and factors for harvest regulation and band reporting methods. Both the band recovery processes and the proportion of individuals recovered in Canada had significant spatial structure. Recovery probabilities were highest in southern Ontario, along the Saint Lawrence River in Quebec, and in Nova Scotia. Black ducks breeding in Nova Scotia and southern Quebec were harvested predominantly in Canada. Recovery probabilities for juveniles were correlated with hunter effort, while the adult recoveries were weakly correlated with the implementation of stricter harvest regulations in the early 1980s. Mean harvest probability decreased in the northern portion of the survey area but remained stable or even increased in the south. Harvest probabilities for juveniles in 2010 exceeded 20% in southern Quebec and the Atlantic provinces. Our results demonstrate fine‐scale variation in harvest probabilities for black duck on the Canadian breeding ground. In particular, harvest probabilities should be closely monitored along the Saint Lawrence River system and in the Atlantic provinces to avoid overexploitation.  相似文献   

17.
Ang  P. O.  Sharp  G. J.  Semple  R. E. 《Hydrobiologia》1993,260(1):321-326
The use of a Norwegian suction cutter to harvest populations of the brown alga Ascophyllum nodosum (L.) Le Jolis in southwestern Nova Scotia started in 1985. The impact of this type of mechanical harvest on the algal population structure was evaluated. Changes in the length and density of individual plants (clumps) within 0.25 m–2 quadrats, as well as the length of individual shoots within clumps were monitored before and after an experimental harvest. The mechanical harvest cut mainly the longer plants, thus changed the initial bimodal size structure of the population to unimodal. There was a 20 to 36% plant mortality, reducing the plant density from 92.6 to 73.6 individuals m–2. Pre-harvest size distribution of the tagged shoots was skewed to the right and became more normal after the harvest. Tagged shoots in the harvested quadrats suffered a 42% mortality as compared to 11% of those in the control quadrats. An understanding of the impact of the mechanical harvesting on the harvested population is essential in the design of a management strategy. Sources of variation in the impact of mechanical harvest include the tide level at time of harvest, length of time the machine operated in one site, skill of the machine operator, and sharpness of the machine cutting blades.  相似文献   

18.
During three decades of research on conifer endophytes of the Acadian forest, numerous insights have been gained in conifer-fungal ecology and secondary metabolite production. Recently, we have explored endophyte assemblages of understory plants commonly occurring with pine. Here we report for the first time the production of the potent antifungal compound griseofulvin by a fungal endophyte isolated from eastern white pine (Pinus strobus) needles and lowbush blueberry (Vaccinium angustifolium) stems from the Acadian forest of New Brunswick and Nova Scotia, Canada. Maximum likelihood phylogenetic analysis has placed the endophyte strains as an undescribed Xylaria sp. Our study highlights the complexity of endophyte-host lifecycles and points to the existence of a pine-blueberry ecotype. Aside from griseofulvin, piliformic acid was isolated from one of the pine endophytes. This compound has been reported from Xylaria and related species but not from Penicillium species known to produce griseofulvin.  相似文献   

19.
Waterfowl management is more effective when based on detailed information on population connectivity between breeding, wintering, and stopover sites. For the American black duck (Anas rubripes), a species of conservation concern, estimates for the fall age ratio at harvest differed depending on whether harvest data were derived from Canada or the United States, suggesting regional differences. Within Canada, hunters in Atlantic Canada were more likely to harvest black ducks from nearby breeding locations compared to hunters in southern Ontario and Quebec, Canada, who were more likely to harvest individuals from the Boreal Softwood and Taiga Shield of eastern Canada. Black ducks harvested in the United States are thought to originate predominantly from northern portions of the breeding range, leading to the flyover hypothesis, which postulates that black ducks produced in the Boreal Softwood and Taiga Shield region are less susceptible to harvest by hunters in Atlantic Canada and northeastern United States. To test the flyover hypothesis, we examined regional and temporal differences in the origins of harvested black ducks using feathers from wings (n = 664) submitted by hunters to the species composition and parts collection surveys across 3 hunting seasons (2017–2018, 2018–2019, 2019–2020). We used a likelihood-based assignment method that relied on feather stable-hydrogen isotopes (δ2H) and stable-carbon isotopes (δ13C) to determine the natal or molt origin of individuals harvested within eastern Canada and the United States. We also used a spatial clustering technique to group harvested individuals by area of origin without a priori knowledge of such regions. Adult female black ducks originated farther south compared to males and juveniles. All sexes and ages of black ducks harvested in Atlantic Canada showed predominantly southern origins, while those harvested in the United States and other Canadian provinces primarily originated farther north within the boreal, supporting the flyover hypothesis. By contrast, we found no relationship between timing of harvest or peaks of migration and individual origin. After combining band returns and stable isotopes, we inferred 2 distinct stocks: the Mississippi flyway stock and the Atlantic flyway stock. We recommend that regional demographic parameters, particularly for Atlantic Canada, be directly measured to promote more effective conservation of black ducks and optimize harvest opportunities in the United States and Canada.  相似文献   

20.
ABSTRACT In Quebec, Canada, harvest of bobcats (Lynx rufus) started to decline in 1985 and by 1991, harvest seasons were closed due to concerns of a perceived population decline. Since the closing of harvest season in 1991, the average temperature has increased, snow quantity has decreased, and important changes in agriculture and forest management have occurred. In light of changing conditions, the situation of Quebec bobcats needed reassessment. Thus, we analyzed harvest data to clarify the current status of bobcat populations in Quebec. From 1980 to 1991, bobcat harvest in Quebec was strongly correlated with bobcat harvest in Maine (USA), Nova Scotia (Canada), Ontario (Canada), and Vermont (USA). Extrapolations of harvest in Quebec relative to harvest in Maine, Ontario, Vermont, and Nova Scotia suggested an increase in number of bobcats after 1991. Mass of male and female bobcats before 1991 was less than mass of animals captured after 1991. Percentage of juveniles in the reported harvest before 1991 was higher than after 1991. However, percentage of males and litter sizes in the harvest did not differ before and after 1991. The geographic distribution of bobcats captured has gradually expanded after the closure of the harvest season. Our findings suggest that bobcat populations in Quebec have recovered from the 1985–1991 decline, and that the harvest season for this species could resume. This study also illustrates how managers can rely on data from neighboring jurisdiction to manage species when local harvest data is unavailable.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号