Hydrographic Effects on the Vertical Distribution of Haddock (Melanogrammus aeglefinus) Eggs and Larvae on the Southwestern Scotian Shelf

1989 ◽  
Vol 46 (S1) ◽  
pp. s82-s92 ◽  
Author(s):  
Kenneth T. Frank ◽  
Fred H. Page ◽  
Jeff K. McRuer
Keyword(s):  
Vertical Distribution ◽  
Depth Distribution ◽  
Stage Iv ◽  
Melanogrammus Aeglefinus ◽  
Juvenile Period ◽  
Embryonic Period ◽  
Near Shore ◽  
The Vertical Distribution ◽  
Eggs And Larvae ◽  
Haddock Melanogrammus Aeglefinus

Relationships between the density (sigma-t) structure of the water column and the depth distribution of haddock (Melanogrammus aeglefinus) eggs and larvae in May of 1985 and 1986 were investigated. During the early embryonic period the egg concentration decreased exponentially with depth; this contrasted sharply with stage IV eggs which showed a subsurface maximum, the location of which was determined by their specific gravity. Depth of the centre-of-mass (Zcrn) of stage IV eggs ranged from 13 to 47 m over the survey area whereas the sigma-t associated with the Zcm depth varied only slightly (CV = 0.4%) about a mean of 25.58. In stratified offshore waters, haddock eggs were aggregated at middepth but exhibited a progressively more uniform vertical distribution towards the weakly stratified nearshore. Where low-density water (sigma-t < 25.5) occurred near-shore eggs were concentrated at the deepest sampling stratum, suggesting that peak egg concentrations were below this level or possibly on the bottom. The depth distribution of haddock larvae was identical to that of late-stage eggs and was therefore established by buoyancy changes occurring during the embryonic period. Day and night Zcm was similar, averaging 28 and 31 m, respectively, and stability of the depth distribution of larvae appears to persist well into the juvenile period.

scholarly journals The vertical separation of fish in the aft end of a demersal trawl

2009 ◽  
Vol 66 (4) ◽  
pp. 772-777 ◽  
Author(s):  
Ludvig Ahm Krag ◽  
René Holst ◽  
Niels Madsen
Keyword(s):  
Vertical Distribution ◽  
Gadus Morhua ◽  
Melanogrammus Aeglefinus ◽  
Multinomial Model ◽  
Vertical Separation ◽  
Commercially Important ◽  
Merlangius Merlangus ◽  
The Vertical Distribution ◽  
Haddock Melanogrammus Aeglefinus ◽  
Important Fish

Abstract Krag, L. A., Holst, R., and Madsen, N. 2009. The vertical separation of fish in the aft end of a demersal trawl. – ICES Journal of Marine Science, 66: 772–777. Two multi-compartment separator frames were used to study the vertical separation of some commercially important fish species in the aft end of a trawl, with the aim of separating cod (Gadus morhua) from other species. A non-linear multinomial model with random effects was used to analyse the data and to compare the performance of the two frames. The vertical distribution of cod in the aft end of the trawl was close to uniform, whereas haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), plaice (Pleuronectes platessa), and lemon sole (Microstomus kitt) showed more uneven distributions. The use of guiding bars in the separator frame significantly (p < 0.05) increased the catch of cod, plaice, and lemon sole in the upper compartment. The vertical separation of cod was density-dependent; high densities of fish resulted in a more uniform distribution of cod. The species separations found differ from those reported from the studies of species separation in the region of the trawl mouth.

Application of a one-dimensional model to vertical distributions of cod eggs on the northeastern Newfoundland Shelf

1995 ◽  
Vol 52 (9) ◽  
pp. 1978-1989 ◽  
Author(s):  
John T. Anderson ◽  
Brad de Young
Keyword(s):  
Vertical Distribution ◽  
Stage Iv ◽  
Dimensional Model ◽  
Temperature Dependent ◽  
One Dimensional ◽  
Poor Condition ◽  
Vertical Distributions ◽  
The Vertical Distribution ◽  
Eggs And Larvae ◽  
Temperature Water

A one-dimensional model is developed to describe the vertical distribution of cod eggs and larvae on the northeastern Newfoundland Shelf. The model is dependent on egg buoyancy, temperature-dependent development, and age-dependent changes in density for eggs in good and poor condition. The model was fit to physical oceanographic data from the inner and outer shelf collected in 1991. Output from the model compared favourably with field observations. Cod eggs (stages I to III) were bimodally distributed above and below 100 m depth. Late stage eggs (stage IV) and larvae (5–6 mm) were only abundant in surface waters (<50 m). There was a progression from deeper to shallower depths as cod eggs developed through to larvae. Cod eggs observed deeper in the water column were thought to be in poor condition and were probably sinking. The model demonstrates that the vertical distribution of cod eggs is sensitive to changes in water temperature, water density (salinity), and egg condition.

A Modified Freeze-Core Technique to Quantify the Depth Distribution of Fauna in Stony Streambeds

1983 ◽  
Vol 40 (5) ◽  
pp. 637-643 ◽  
Author(s):  
C. W. Pugsley ◽  
H. B. N. Hynes
Keyword(s):  
Vertical Distribution ◽  
Liquid Nitrogen ◽  
Benthic Invertebrates ◽  
Depth Distribution ◽  
Sampling Methods ◽  
Freezing Front ◽  
Southern Ontario ◽  
Freeze Core ◽  
Order Of Magnitude ◽  
The Vertical Distribution

A freeze-coring device using liquid nitrogen is described, which enables one person to take a columnar core, extending from the surface to at least 50 cm below a stony streambed. An experiment to validate the technique showed that animals did not flee from the advance of the freezing-front. Using frozen streambed cores, the vertical distribution of benthic invertebrates of two streams in southern Ontario was investigated. In contrast to previous estimates,~70% of the fauna was found in the top 10 cm of the streambed, and invertebrate densities were often lower by an order of magnitude. These differences are attributed to problems of quantifying previous sampling methods.

Distribution and Abundance of Haddock (Melanogrammus aeglefinus) and Atlantic Cod (Gadus morhua) Eggs and Larvae in the Waters off Southwest Nova Scotia

1989 ◽  
Vol 46 (S1) ◽  
pp. s103-s112 ◽  
Author(s):  
Peter C. F. Hurley ◽  
Steven E. Campana
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Melanogrammus Aeglefinus ◽  
Eggs And Larvae ◽  
Haddock Melanogrammus Aeglefinus ◽  
Egg Abundance

Synoptic ichthyoplankton surveys conducted at monthly intervals during the winter–spring of 1983–85 were used to determine the location, timing, and magnitude of spawning by haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua) off southwest Nova Scotia. There was a marked similarity in the spawning locations of the two species: primary spawning occurred on Browns Bank, although lower levels of spawning were observed on adjacent banks and in the inshore region. Cod egg abundance peaked in April in all years, while that of haddock varied between April–June.

The Vertical Distribution of Pelagic Decapods [Crustacea: Natantia] Collected on the Sond Cruise 1965 II. The Penaeidea and General Discussion

1970 ◽  
Vol 50 (4) ◽  
pp. 961-1000 ◽  
Author(s):  
P. Foxton
Keyword(s):  
Vertical Distribution ◽  
North Atlantic ◽  
Depth Distribution ◽  
Final Part ◽  
Decapod Crustaceans ◽  
Eastern North Atlantic ◽  
And Migration ◽  
The Vertical Distribution ◽  
Diurnal Migration

This paper represents the second and final part of a study of the depth distribution and diurnal migration of pelagic decapod crustaceans in an area of the eastern North Atlantic. Part I (Foxton, 1970) dealt with the Caridea; Part II now considers the Penaeidea. In the discussion the data as a whole are analysed and the resulting patterns of vertical distribution and migration discussed.

Observations on the Vertical Distribution of Eggs and Larvae of Mackerel and other Teleosts in the Celtic Sea and on the Sampling Performance of Different Nets in Relation to Stock Evaluation

1980 ◽  
Vol 60 (2) ◽  
pp. 295-311 ◽  
Author(s):  
A. J. Southward ◽  
B. McK. BARY
Keyword(s):  
Vertical Distribution ◽  
Geographical Pattern ◽  
Spawning Grounds ◽  
The Past ◽  
South West ◽  
Complete Survey ◽  
Celtic Sea ◽  
The Vertical Distribution ◽  
Eggs And Larvae ◽  
Made In

There is some controversy about the strength of the stock of mackerel in the Celtic Sea and off the coasts of Cornwall and Ireland, and it is difficult to find out if the numbers of mackerel in this area have fluctuated in the past (Johnson, 1977; Lockwood & Johnson, 1976; Lockwood, 1978; Coombs, Pipe & Mitchell, 1977,1979, 1980). The earliest complete survey of the south-west spawning grounds was made in 1937–9 (Steven & Corbin, 1939; Corbin, 1947) and was principally designed to show the seasonal and geographical pattern, not provide a basis for stock evaluation. Nevertheless, this survey is the only information we have about the breeding of mackerel in the days before the war when fishing was performed with drift-nets and lines, a period when we can assume exploitation was very much less intense than today when trawls and purse-seines are used. Attempts to use the 1937–9 data for estimation of the pre-war stock have been regarded as giving unsatisfactory results (Walsh, 1976). The data from the 1937–9 surveys were defective because we did not know the influence of the depth of fishing of the nets in relation to the vertical distribution of the eggs, nor the efficiency and catching capacity of the nets for sampling eggs and post-larvae.

Sign in / Sign up

Export Citation Format

Share Document