Stock Structure of Scotian Shelf Flatfish as Inferred from Ichthyoplankton Survey Data and the Geographic Distribution of Mature Females

1988 ◽  
Vol 45 (10) ◽  
pp. 1674-1685 ◽  
Author(s):  
J. D. Neilson ◽  
E. M. DeBlois ◽  
P. C. F. Hurley
Keyword(s):  
Stock Assessment ◽  
Stock Structure ◽  
Stock Identification ◽  
Scotian Shelf ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Valuable Adjunct ◽  
Commercially Important ◽  
Eggs And Larvae ◽  
Sexually Mature

Data on egg distributions and timing of appearance of maximum egg densities were examined to determine the stock structure of three commercially important flatfish occurring on the Scotian Shelf: American plaice (Hippoglossoides platessoides), yellowtail flounder (Limanda ferruginea), and witch flounder (Glyptocephalus cynoglossus). Distributions of sexually mature females obtained from research vessel surveys were used to further support inferences concerning spawning location. Using such information, more than one stock of both American plaice and yellowtail flounder appear to occur on the Scotian Shelf, but no conclusions could be drawn concerning witch flounder. In the case of American plaice and yellowtail flounder, the existing means of geographic aggregation of data for stock assessment purposes do not appear to adequately represent stock structure. Little or no advection of eggs and larvae appears to occur on the Scotian Shelf, supporting the hypothesis that current-driven retention areas promote stock discreteness in that region. It was concluded that ichthyoplankton surveys can be a valuable adjunct to more traditional means of stock identification.

Eggs and Larvae of Northern Sand Lance (Ammodytes dubius) from the Scotian Shelf

1972 ◽  
Vol 29 (12) ◽  
pp. 1667-1671 ◽  
Author(s):  
J. S. Scott
Keyword(s):  
Growth Rates ◽  
Scotian Shelf ◽  
Sand Lance ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Dorsal Fin ◽  
The North ◽  
Mean Diameter ◽  
Fin Rays ◽  
Eggs And Larvae

Eggs from stomachs of yellowtail flounder (Limanda ferruginea) from Emerald Bank, south of Nova Scotia, were identified as those of northern sand lance, Ammodytes dubius. They were larger than those of other Ammodytes species, with a mean diameter of 1.05 mm. Ovarian eggs from ripe A. dubius were smaller (mean diameter 0.7 mm) with a unimodal distribution of egg diameters, indicating a single spawning each season.Larvae were widespread and abundant on the Scotian Shelf from February to April. They hatched at about 4-mm length and grew to about 25-mm length between February and May on Emerald Bank. Growth rates decreased to the north. Numbers and distribution of melanophores changed with larval length, but showed no differences in number at given length between geographical areas. Change in numbers of anal, caudal, and dorsal fin rays followed a pattern similar to that of corresponding melanophores.

Digenean parasite communities in flatfishes of the Scotian Shelf and southern Gulf of St. Lawrence

1982 ◽  
Vol 60 (11) ◽  
pp. 2804-2811 ◽  
Author(s):  
J. S. Scott
Keyword(s):  
Feeding Behavior ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Parasite Prevalence ◽  
Winter Flounder ◽  
Fish Length ◽  
Pseudopleuronectes Americanus ◽  
Scotian Shelf ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea

Prevalence of digenean parasites in four major flatfishes of the Scotian Shelf and southern Gulf of St. Lawrence, American plaice (Hippoglossoides platessoides), yellowtail flounder (Limanda ferruginea), witch flounder (Glyptocephalus cynoglossus), and winter flounder (Pseudopleuronectes americanus), is compared between hosts in relation to geographic distribution, season, feeding behavior, and fish length. The 13 parasite species indicate overlap of feeding habits among hosts but also considerable diversity in feeding behavior, supporting the evidence from examination of stomach contents. Prevalence of digeneans in different final hosts varied between geographic areas and may be used to characterize the populations of the comparatively sedentary flatfish populations. Seasonal variation in prevalence was consistent from area to area but differed between parasites, from the expected increase in summer in some, concomitant with increased feeding, to a winter increase in others, probably related to a seasonal change of diet. Fish length had little effect on parasite prevalence in yellowtail flounder and witch flounder but had a notable effect on plaice and winter flounder from the Gulf of St. Lawrence, again apparently related to change of diet.

scholarly journals Demonstration of a spatially explicit, tag-integrated stock assessment model with application to three interconnected stocks of yellowtail flounder off of New England

2014 ◽  
Vol 72 (1) ◽  
pp. 164-177 ◽  
Author(s):  
Daniel R. Goethel ◽  
Christopher M. Legault ◽  
Steven X. Cadrin
Keyword(s):  
New England ◽  
Integrated Assessment ◽  
Stock Assessment ◽  
Assessment Model ◽  
Spatially Explicit ◽  
Closed Population ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Stock Assessments ◽  
Source Sink

Abstract Ignoring population structure and connectivity in stock assessment models can introduce bias into important management metrics. Tag-integrated assessment models can account for spatially explicit population dynamics by modelling multiple population components, each with unique demographics, and estimating movement among them. A tagging submodel is included to calculate predicted tag recaptures, and observed tagging data are incorporated in the objective function to inform estimates of movement and mortality. We describe the tag-integrated assessment framework and demonstrate its use through an application to three stocks of yellowtail flounder (Limanda ferruginea) off New England. Movement among the three yellowtail flounder stocks has been proposed as a potential source of uncertainty in the closed population assessments of each. A tagging study was conducted during 2003–2006 with over 45 000 tagged fish released in the region, and the tagging data were included in the tag-integrated model. Results indicated that movement among stocks was low, estimates of stock size and fishing mortality were similar to those from conventional stock assessments, and incorporating stock connectivity did not resolve residual patterns. Despite low movement estimates, new interpretations of regional stock dynamics may have important implications for regional fisheries management given the source-sink nature of movement estimates.

Distribution, Abundance, and Spawning of Yellowtail Flounder, Limanda ferruginea, in the Newfoundland Area of the Northwest Atlantic

1970 ◽  
Vol 27 (12) ◽  
pp. 2261-2271 ◽  
Author(s):  
T. K. Pitt
Keyword(s):  
Drastic Reduction ◽  
Upward Trend ◽  
Northwest Atlantic ◽  
Spawning Period ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Far North ◽  
Sexually Mature

Yellowtail flounder were found as far north as the Strait of Belle Isle; however, the main concentrations were located on Grand and St. Pierre banks. The highest concentrations were found at 31–35 fath (57–64 m) and temperatures of 3.1–4.8 C. Abundance on the Grand Bank apparently increased from 1961 to 1968 coincident with a general upward trend in bottom temperatures and a drastic reduction in the haddock population. The peak spawning period was the latter half of June. Fifty percent of the males were sexually mature at age 5 and 31 cm, and 50% of females at age 6 and 37 cm.

scholarly journals Genetic identification of hake and megrim eggs in formaldehyde-fixed plankton samples

2005 ◽  
Vol 62 (5) ◽  
pp. 908-914 ◽  
Author(s):  
Juliana Perez ◽  
Paula Álvarez ◽  
Jose L. Martinez ◽  
Eva Garcia-Vazquez
Keyword(s):  
Stock Assessment ◽  
Pcr Amplification ◽  
Species Specificity ◽  
Genetic Identification ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Merluccius Merluccius ◽  
Commercially Important ◽  
Eggs And Larvae ◽  
European Hake

Abstract Spawning of European hake (Merluccius merluccius) and megrim (Lepidorhombus whiffiagonis and L. boscii) overlap in time and space. Their eggs are morphologically similar, so genetic identification is needed for purposes of stock assessment based on plankton surveys. Amplification fragment sizes of a partial sequence within the 16S rRNA genes are different for Merluccius merluccius, Lepidorhombus boscii, and L. whiffiagonis. Species-specificity of the pattern was confirmed after analysing adult individuals from all distribution areas of the three species. After Chelex-based DNA extraction and PCR amplification, fragment sizes at this gene were successfully determined from 85% formaldehyde-fixed eggs and larvae recovered from plankton samples. Species-specificity was resolved using an ABI genetic analyser. The results were 100% reproducible. This methodology for genetic identification of hake and megrim eggs can be very useful for stock assessment of these three commercially important fish species.

Age Composition and Growth of Yellowtail Flounder (Limanda ferruginea) from the Grand Bank

1974 ◽  
Vol 31 (11) ◽  
pp. 1800-1802 ◽  
Author(s):  
T. K. Pitt
Keyword(s):  
New England ◽  
Growth Curves ◽  
Scotian Shelf ◽  
Age Composition ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Similar Growth

The commercial yellowtail flounder (Limanda ferruginea) fishery on the Grand Bank is comprised of fish age 4–12 with the main contribution from 6–8-yr-olds. Comparison of Grand Bank yellowtail with those reported for the Scotian Shelf indicates similar growth curves. The New England stocks are significantly larger at comparable age probably because of higher water temperatures.

Testing the performance of a spatially explicit tag-integrated stock assessment model of yellowtail flounder (Limanda ferruginea) through simulation analysis

2015 ◽  
Vol 72 (4) ◽  
pp. 582-601 ◽  
Author(s):  
Daniel R. Goethel ◽  
Christopher M. Legault ◽  
Steven X. Cadrin
Keyword(s):  
Stock Assessment ◽  
Population Models ◽  
Assessment Model ◽  
Spatially Explicit ◽  
Parameter Estimates ◽  
Integrated Models ◽  
Closed Population ◽  
Yellowtail Flounder ◽  
Limanda Ferruginea ◽  
Wide Range

In any stock assessment application, the implicit assumptions regarding spatial population structure must be carefully evaluated. Tag-integrated models offer a promising approach for incorporating spatial structure and movement patterns in stock assessments, but the complexity of the framework makes implementation challenging and the appraisal of performance difficult. A flounder-like fishery was simulated to emulate the metapopulation dynamics of the three yellowtail flounder (Limanda ferruginea) stocks off New England, and the robustness of spatially explicit tag-integrated models were compared with closed population assessments. Different movement parametrizations and data uncertainty scenarios were simulated, while the ability of the tag-integrated model to estimate reporting rate and time-varying movement were also evaluated. Results indicated that the tag-integrated framework was robust for the simulated fishery across a wide range of connectivity levels and that tag reporting rates were accurately estimated. Closed population models also demonstrated limited error. Therefore, spatially explicit approaches may not always be warranted even when regional connectivity is occurring, but tag-integrated models can provide improved parameter estimates when reliable tagging data are available. Tag-integrated models also serve as valuable tools for informing spatially explicit operating models, which can then be used to evaluate the assumptions and performance of closed population models.

scholarly journals THE PERIOD OF THE CATTLE BUNOSTOM DEVELOPMENT OF THE IN THE AMUR REGION

2019 ◽  
pp. 128-132
Author(s):  
T. I. Trukhina ◽  
I. A. Solovieva ◽  
G. A. Bonadrenko
Keyword(s):  
Infection Rate ◽  
Small Ruminants ◽  
Amur Region ◽  
Mature Stage ◽  
Economic Damage ◽  
Veterinary Science ◽  
Age Related ◽  
Eggs And Larvae ◽  
Sexually Mature ◽  
Cattle And Sheep

The authors focus on the fight against the most common helminthic diseases of agricultural animals as they see it as an important part of the veterinary science. Bunostomosis is one of such diseases; it is a helminthiasis of ruminants caused by vipostomum trigonocephalum nematodes (in sheep and goats) and vipostomum phlebotomum (mainly in the cattle), which are parasitic in the small intestines. The disease is characterized by diarrhea, exhaustion and death of ruminants. The disease is widespread and causes great economic damage. The authors explored the prevalence of tuberculosis and age-related infection with tuberculosis by ovoscopy and levoscopy in the Amur region. They examined 2655 animals, including 1415 small ruminants and 1240 cattle from five districts of the Amur region. The researchers examined 4 calves and 4 lambs aged 4 inorder to study the period of bunostom development in the organism of animals, which were infected with percutaneously and orally. Brown larvae received from faeces of spontaneously infested animals is considered to be the material for infection. The development and survival of larvae in the environment were investigated in 2016-2017. The authors found out that in the Amur region larvae develop at the temperatures above 40С. The period of development at the temperature from 40С tо 9 0С was 23 days. When the temperature was increasing, the development period was reduced to 5-7 days. In October larvae stop their development. The underdeveloped eggs and larvae left die in winter. At the farms of the Amur region, the infection rate of cattle and sheep is 31.9 and 49.6%. The bunostome infection of the cattle aged 1-11 months is 59,8%; 1-2 years - 26,0; 3 years and more - 19,9; sheep aged 4-11 months infection rate is 52,9; 1 year - 60,9, 3 years and more - 38,7%. The authors observed bunostomes development during 89-102 days in the ruminant organism before the sexually mature stage in the conditions of the Amur region.

Nonstationarity of Production Relationships in Exploited Populations

1987 ◽  
Vol 44 (S2) ◽  
pp. s156-s165 ◽  
Author(s):  
Carl J. Walters
Keyword(s):  
Environmental Changes ◽  
Historical Data ◽  
Stock Assessment ◽  
Policy Implications ◽  
Data Sets ◽  
Stock Structure ◽  
Stock Size ◽  
Rate Processes ◽  
And Shifts ◽  
Time Invariant

Stock assessment usually proceeds from the assumption that there are time-invariant relationships between stock size and rate processes such as recruitment, although such relationships are difficult to discern due to noise caused by factors other than stock size. There are good biological reasons not to trust this assumption in exploited populations, where persistent environmental changes and shifts in stock structure may cause various parameters to change. Graphical and statistical procedures can be used to detect this nonstationarity in historical data sets for which stock size has varied so as to repeatedly sample a range of sizes. The policy implications of nonstationarity depend on whether the changes are clearly observable as deviations from known, Song-term baseline responses. If the changes are observable, it is usually best to pretend that the current deviation will persist unless strong constraints on policy change make it necessary to plan for changes that may occur far into the future. If the changes are not observable (the usual case), then it is necessary to make a difficult policy choice between passively waiting for informative stock responses versus actively experimenting with harvest rates so as to quickly get information about responses over a range of stock sizes.

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