Annual egg production estimates of cod (Gadus morhua), plaice (Pleuronectes platessa) and haddock (Melanogrammus aeglefinus) in the Irish Sea: The effects of modelling choices and assumptions

2012 ◽  
Vol 117-118 ◽  
pp. 146-155 ◽  
Author(s):  
David L. Maxwell ◽  
Michael J. Armstrong ◽  
Steven Beggs ◽  
John N. Aldridge
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Irish Sea ◽  
Melanogrammus Aeglefinus ◽  
Pleuronectes Platessa ◽  
The Irish Sea ◽  
Haddock Melanogrammus Aeglefinus

Diet overlap and prey selection through metamorphosis in Irish Sea cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and whiting (Merlangius merlangus)

2008 ◽  
Vol 65 (7) ◽  
pp. 1297-1306 ◽  
Author(s):  
William Ll. Rowlands ◽  
Mark Dickey-Collas ◽  
Audrey J. Geffen ◽  
Richard D.M. Nash
Keyword(s):  
Gadus Morhua ◽  
Prey Selection ◽  
Stomach Contents ◽  
Irish Sea ◽  
Melanogrammus Aeglefinus ◽  
Prey Preferences ◽  
Merlangius Merlangus ◽  
The Irish Sea ◽  
Haddock Melanogrammus Aeglefinus ◽  
Calanus Species

Copepods in the genus Calanus are usually considered to be the preferred prey of gadoid larvae in many areas; however, in the Irish Sea, the abundances of these Calanus species are low and highly variable. We use this situation to test whether Calanus species are still actively selected by gadoid larvae in Calanus -poor environments. Diets of Irish Sea cod ( Gadus morhua ), haddock ( Melanogrammus aeglefinus ), and whiting ( Merlangius merlangus ) were studied from the yolk-sac stage to the juvenile stage. Prey from stomach contents were compared with in situ abundance via an index of prey preference. As expected, all larvae selected copepod nauplii at the onset of feeding. As the larvae developed, their prey preferences changed and varied with species. Cod and whiting showed a similar transition of prey species preference, with a clear preference for Calanus species after metamorphosis, even in this area of low abundance of these Calanus species. The diet composition of haddock differed from that of cod and whiting, as nauplii remained in their diet later into development and there was little preference for individual copepod species detected. The differences in prey selectivity suggested between these gadoids may be attributed to their population variability through the known variability of their preferred prey items.

scholarly journals Fishery discards in the Irish Sea exhibit temporal oscillations and trends reflecting underlying processes at an annual scale

2010 ◽  
Vol 68 (1) ◽  
pp. 221-227 ◽  
Author(s):  
Mafalda Viana ◽  
Norman Graham ◽  
James G. Wilson ◽  
Andrew L. Jackson
Keyword(s):  
Gadus Morhua ◽  
Temporal Dynamics ◽  
Stock Assessment ◽  
Irish Sea ◽  
Melanogrammus Aeglefinus ◽  
Annual Cycles ◽  
The Irish Sea ◽  
Fishery Discards ◽  
Annual Scale ◽  
Underlying Processes

Abstract Viana, M., Graham, N., Wilson, J. G., and Jackson, A. L. 2011. Fishery discards in the Irish Sea exhibit temporal oscillations and trends reflecting underlying processes at an annual scale. – ICES Journal of Marine Science, 68: 221–227. Non-inclusion of discard data in stock assessment can lead to underestimation of biomass and fishing mortality; this is of particular concern if there have been changes in discard practices over time. Although variability in space and time is a well-documented feature of discards, the temporal dynamics of the practice has received little detailed attention. The aim here is to characterize the temporal patterns of discarding practices in the Irish Sea (ICES Division VIIa) from 1994 to 2008. Trend and seasonality were explored in discards per unit effort (dpue) of haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and cod (Gadus morhua) through Bayesian harmonic regression (HREG) models. The HREG models reveal discarding of all three species in annual cycles, with a peak in the second quarter, perhaps reflecting species biology or fisher behaviour, or both. The dpue of cod cycled around a constant level throughout the observation period, but whiting and haddock dpue increased.

Recent Growth, Biochemical Composition and Prey Field of Larval Haddock (Melanogrammus aeglefinus) and Atlantic Cod (Gadus morhua) on Georges Bank

1987 ◽  
Vol 44 (1) ◽  
pp. 14-25 ◽  
Author(s):  
L. J. Buckley ◽  
R. G. Lough
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Dry Weight ◽  
Melanogrammus Aeglefinus ◽  
Good Growth ◽  
Georges Bank ◽  
Larval Population ◽  
Prey Biomass ◽  
Recent Growth ◽  
Haddock Melanogrammus Aeglefinus

A transect across southern Georges Bank in May 1983 showed higher levels of available prey for haddock (Melanogrammus aeglefinus) and cod (Gadus morhua) larvae at two stratified sites than at a well-mixed site. At the stratified sites, prey biomass was high (30–300 μg dry wt∙L−1) near the surface above the thermocline; values were lower and more uniform with depth (10–30 μg dry wt∙L−1) at the well-mixed site. Larval population centers generally coincided with prey biomass vertically. Recent growth in dry weight of haddock larvae as estimated by RNA–DNA ratio analysis was higher at the stratified sites (8–13%∙d−1) than at the well-mixed site (7%∙d−1). Larvae appeared to be in excellent condition at the stratified sites, but up to 50% of haddock larvae from the well-mixed site had RNA–DNA ratios in the range observed for starved larvae in the laboratory. Cod collected at the same site were in better condition and growing faster than haddock. The data support the hypotheses that (1) stratified conditions in the spring favor good growth and survival of haddock larvae and (2) cod larvae are better adapted to grow and survive in well-mixed waters at lower levels of available food than haddock larvae.

Distinguishing Between One-Day-Old Cod (Gadus morhua) and Haddock (Melanogrammus aeglefinus) Eggs by Gas Chromatography and SIMCA Pattern Recognition

1985 ◽  
Vol 42 (11) ◽  
pp. 1823-1826 ◽  
Author(s):  
H. Knutsen ◽  
E. Moksnes ◽  
N. B. Vogt
Keyword(s):  
Fatty Acids ◽  
Pattern Recognition ◽  
Gas Chromatography ◽  
Multivariate Analysis ◽  
Methyl Ester ◽  
Gadus Morhua ◽  
Melanogrammus Aeglefinus ◽  
One Step ◽  
High Resolution Gas Chromatography ◽  
Haddock Melanogrammus Aeglefinus

Single cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) eggs were acid hydrolized. All the fatty acids were liberated and converted to methyl ester in a one-step reaction. The nonpolar hexane extract was analyzed by high resolution gas chromatography (HRGC). Selected peaks, occurring in both types of samples and in all chromatograms, were used to create a matrix for multivariate analysis. We conclude that cod and haddock eggs can be distinguished using this method.

scholarly journals On the Food of Young Plaice (Pleuronectes platessa)

1922 ◽  
Vol 12 (4) ◽  
pp. 678-687 ◽  
Author(s):  
Andrew Scott
Keyword(s):  
Present Report ◽  
Stomach Contents ◽  
Annual Reports ◽  
Irish Sea ◽  
Pleuronectes Platessa ◽  
Larval Stages ◽  
Marine Biological Association ◽  
Open Sea ◽  
Pelagic Eggs ◽  
The Irish Sea

The investigation of the food contents in the stomachs of young fishes was included in the scheme of scientific investigations drawn up and initiated by Professor Herdman for the Lancashire Sea Fisheries Committee nearly thirty years ago. The lengthy series of Annual Reports contain here and there accounts of the observations made on the stomach contents of various Pleuronectidæ captured close inshore, and the pelagic stages of other fishes caught from time to time in the plankton tow-nets. No systematic attempt has, however, been made, in connection with the investigation of the Irish Sea, to determine the food of any particular species of fish during the early part of its life history.Other observers working in other areas, notably Dr. Marie Lebour at Plymouth, have added very much to our knowledge of the early food of young fishes. Dr. Lebour's reports, published in the Journal of the Marine Biological Association, Vols. XI and XII, deal with a very large number of larval and post-larval stages of the more important food fishes caught in the tow-nets and young fish-trawl in Plymouth Sound and beyond.The present report gives an account of the food contained in the stomachs of young plaice (Pleuronectes platessa, Linn.) from a few days after hatching to about five months old. The samples examined in April and May were taken from the spawning pond at Port Erin, Isle of Man, where they had hatched from the pelagic eggs spawned by the adult plaice early in 1921. The later stages examined during May to August represented young plaice hatched in the open sea about the same time as those in the pond, and which had made their way close inshore.

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