Reply to the comment by Payne et al. on “Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus, through parental condition?”Appears in Can. J. Fish. Aquat. Sci. 65: 1076–1086.

2009 ◽  
Vol 66 (5) ◽  
pp. 873-877 ◽  
Author(s):  
Kevin D. Friedland ◽  
Jonathan A. Hare ◽  
Grayson B. Wood ◽  
Laurel A. Col ◽  
Lawrence J. Buckley ◽  
...  
Keyword(s):  
Phytoplankton Bloom ◽  
Explanatory Variable ◽  
Zooplankton Biomass ◽  
Melanogrammus Aeglefinus ◽  
Georges Bank ◽  
Parental Condition ◽  
Bloom Control ◽  
Haddock Melanogrammus Aeglefinus ◽  
Recruitment Time

Payne et al. (Can. J. Fish. Aquat. Sci. 66: 869–872, 2009) raised several points concerning the handling and interpretation of data that went into an analysis of the population dynamics of Georges Bank haddock that suggested a relationship between the fall phytoplankton bloom and recruitment (Can. J. Fish. Aquat. Sci. 65: 1076–1086, 2008). Their main points were the manner in which logarithmic transforms were applied, whether the 2003 year class was truly as large as estimated in a 2006 assessment, and if correlation analyses of zooplankton data should be reconsidered. The reply to these comments was aided by a new assessment which provided additional years of data and improved the quality of the recruitment time series. The reply analyses showed that the relationships were robust to the way the logarithmic transform was applied, the initial estimates of the size of the 2003 year class were correct, and relationships between recruitment and spring zooplankton biomass levels remain statistically insignificant. From these new analyses, the interpretations and conclusions reached in the original paper remain the same; the fall bloom has emerged as a candidate explanatory variable for the stock independent variation in haddock recruitment on Georges Bank.

Comment on “Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus, through parental condition?”Appears in Can. J. Fish. Aquat. Sci. 65: 1076–1086.

2009 ◽  
Vol 66 (5) ◽  
pp. 869-872 ◽  
Author(s):  
Mark R. Payne ◽  
Mark Dickey-Collas ◽  
Richard D.M. Nash
Keyword(s):  
Phytoplankton Bloom ◽  
Uncertain Data ◽  
Melanogrammus Aeglefinus ◽  
Georges Bank ◽  
Alternative Hypotheses ◽  
Parental Condition ◽  
Bloom Control ◽  
Haddock Melanogrammus Aeglefinus ◽  
Sizable Number ◽  
Main Factor

In the paper “Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus , through parental condition?”, Friedland et al. (Can. J. Fish. Aquat. Sci. 65(6): 1076–1086, 2008) examine a sizable number of hypotheses aiming to explain the recruitment patterns observed in Georges Bank haddock. The authors focus on a correlation between the size of the autumnal phytoplankton bloom and the survivor ratio (recruitment), concluding this to be the main factor determining recruitment, via the mechanism of adult condition at the time of spawning. Here we examine this result in close detail and re-analyse some of the data presented in the paper. We show that the recruitment metric upon which Friedland et al. base their conclusions inadvertently biases the analysis in favour of high recruitment events and against low recruitments. As a consequence, Friedland et al. disregard correlations that are, in fact, significant. Furthermore, we show that the parental condition hypothesis hinges upon a single, highly uncertain data point, without which the correlation is no longer significant. We find that evidence for the parental condition hypothesis is weak, and that in performing the analysis in the chosen manner, Friedland et al. have overlooked alternative hypotheses.

Does the fall phytoplankton bloom control recruitment of Georges Bank haddock, Melanogrammus aeglefinus, through parental condition?

2008 ◽  
Vol 65 (6) ◽  
pp. 1076-1086 ◽  
Author(s):  
Kevin D. Friedland ◽  
Jonathan A. Hare ◽  
Grayson B. Wood ◽  
Laurel A. Col ◽  
Lawrence J. Buckley ◽  
...  
Keyword(s):  
Phytoplankton Bloom ◽  
Larval Growth ◽  
Melanogrammus Aeglefinus ◽  
Georges Bank ◽  
Growth And Survival ◽  
Probability Of Survival ◽  
Bank Stock ◽  
Parental Condition ◽  
Recruitment Event ◽  
Haddock Melanogrammus Aeglefinus

In 2003, the Georges Bank stock of haddock ( Melanogrammus aeglefinus ) experienced the largest recruitment event recorded during its assessed history. Several hypotheses have been advanced to explain recruitment variability in this much-scrutinized stock, including variability in the retention of eggs and larvae on Georges Bank, the timing of haddock spawning, and variability in the spring bloom, which influences larval growth and survival. Although these processes may contribute to the formation of successful year classes, none of the factors associated with these previous hypotheses provides an adequate explanation of the 2003 recruitment event. We analyzed data on the dynamics of the fall phytoplankton bloom the year prior to spawning and show it to be highly correlated with subsequent recruitment. We suggest that the fall bloom affects recruitment through enhanced condition of adults and by increasing the quantity and quality of their reproductive output, which in turn leads to a higher probability of survival of their offspring. Although synoptic data on the fall bloom are limited and our analyses are correlative, our purpose is to stimulate a rigorous test of this promising “parental condition hypothesis”.

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.

Recruitment Variability and Its Implication for Managing and Rebuilding the Georges Bank Haddock (Melanogrammus aeglefinus) Stock

1986 ◽  
Vol 43 (4) ◽  
pp. 748-753 ◽  
Author(s):  
William J. Overholtz ◽  
Michael P. Sissenwine ◽  
Stephen H. Clark
Keyword(s):  
Melanogrammus Aeglefinus ◽  
Georges Bank ◽  
Fishing Mortality ◽  
Initial Strategy ◽  
Low Probability ◽  
The Relationship ◽  
Constant Growth ◽  
Spawning Biomass ◽  
Haddock Melanogrammus Aeglefinus ◽  
Stock Recovery

The Georges Bank haddock (Melanogrammus aeglefinus) fishery has fluctuated dramatically since the early 1960's. Abundance declined from the mid-1960's to the mid-1970's, partially recovered, and has declined again since 1980. In general, poor year-classes have been associated with a low spawning biomass although the relationship is variable. The fishery was simulated by using the Baranov catch equation, constant growth and natural mortality, and stochastic levels of recruitment whose probabilities correspond to historic patterns in the stock and recruitment data. Simulations suggest a low probability for stock recovery and improved yield under current conditions (F ≈ 0.5). Recovery time increased with increases in fishing mortality (F), and beyond F = 0.40 recovery is unlikely within 25 yr. With recruitment of a very large year-class (100 million fish) an initial strategy providing for a relatively low level of F(= 0.10) for 3−5 yr, followed by exploitation at historically sustainable levels (F = 0.35), would result in stock recovery. With recruitment of a smaller year-class (50 million fish) low initial levels (F = 0.10) and subsequent management at or near F0.1 (F = 0.26) would be required to initiate stock recovery and reasonable harvest levels in future years.

scholarly journals Fecundity estimation of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) of Georges Bank: Application of the autodiametric method

2009 ◽  
Vol 99 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Alexandre Alonso-Fernández ◽  
Ann Carole Vallejo ◽  
Fran Saborido-Rey ◽  
Hilario Murua ◽  
Edward A. Trippel
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Melanogrammus Aeglefinus ◽  
Georges Bank ◽  
Haddock Melanogrammus Aeglefinus
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