The growing degree-day and fish size-at-age: the overlooked metric

2007 ◽  
Vol 64 (2) ◽  
pp. 375-385 ◽  
Author(s):  
Anna B Neuheimer ◽  
Christopher T Taggart
Keyword(s):  
Growth And Development ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Variable Temperature ◽  
Spatial Scales ◽  
Explanatory Power ◽  
Field Studies ◽  
Fish Length ◽  
Degree Day ◽  
Size At Age

Growth rate in ectotherms, including most fish, is a function of temperature. For decades, agriculturalists (270+ years) and entomologists (45+ years) have recognized the thermal integral, known as the growing degree-day (GDD, °C·day), to be a reliable predictor of growth and development. Fish and fisheries researchers have yet to widely acknowledge the power of the GDD in explaining growth and development among fishes. We demonstrate that fish length-at-day (LaD), in most cases prior to maturation, is a strong linear function of the GDD metric that can explain >92% of the variation in LaD among 41 data sets representing nine fish species drawn from marine and freshwater environments, temperate and tropical climes, constant and variable temperature regimes, and laboratory and field studies. The GDD demonstrates explanatory power across large spatial scales, e.g., 93% of the variation in LaD for age-2 to -4 Atlantic cod (Gadus morhua) across their entire range (17 stocks) is explained by one simple GDD function. Moreover, GDD can explain much of the variation in fish egg development time and in aquatic invertebrate (crab) size-at-age. Our analysis extends the well-established and physiologically relevant GDD metric to fish where, relative to conventional time-based methods, it provides greater explanatory power.

Depth-dependent vertebral number of Atlantic cod (Gadus morhua) on the Magdalen Shallows and Scotian Shelf: stock mixing or microgeographic trends within populations?

2000 ◽  
Vol 57 (12) ◽  
pp. 2393-2401 ◽  
Author(s):  
D P Swain ◽  
K T Frank
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Relative Length ◽  
Scotian Shelf ◽  
Age Classes ◽  
Vertebral Number ◽  
Size At Age ◽  
Stock Mixing ◽  
Summer Feeding

We examined spatial variation in the vertebral number of Atlantic cod (Gadus morhua) during the summer feeding season in the southern Gulf of St. Lawrence and on the Scotian Shelf. Mean vertebral number increased significantly with depth in the southern Gulf and on the northeastern Scotian Shelf but not on the southwestern Scotian Shelf. In the southern Gulf, where sampling was most extensive, mean vertebral number increased steadily as depth increased from 25 m to over 175 m. Mean vertebral number was also strongly related to relative length within age-classes, with the larger fish at age having more vertebrae. However, the association between vertebral number and depth could not be attributed to confounding between depth and size at age. These results indicate either unexpected mixing between neighbouring cod populations or unexpected structure at fine spatial scales within cod populations.

scholarly journals Regional variation in otolith geochemistry of juvenile Atlantic cod (Gadus morhua) in coastal Newfoundland

2016 ◽  
Vol 73 (10) ◽  
pp. 1507-1519 ◽  
Author(s):  
Ryan R.E. Stanley ◽  
Claudio DiBacco ◽  
Simon R. Thorrold ◽  
Paul V.R. Snelgrove ◽  
Corey J. Morris ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Environmental Variability ◽  
Atlantic Cod ◽  
Environmental Influence ◽  
Spatial Scales ◽  
Early Life History ◽  
Otolith Chemistry ◽  
Geographic Patterns ◽  
Assignment Success ◽  
Scale Classification

We examined spatial variation in otolith geochemistry as a natural tag in juvenile Atlantic cod (Gadus morhua) to resolve geographic patterns during early life history. Individuals from 54 inshore sites spanned five embayments in eastern Newfoundland. Otolith composition differed at all spatial scales and related inversely to spatial scale. Classification analysis revealed increasing discrimination at coarser spatial scales: site (26%–58%), bay (49%), and coast (76%). Assignment success declined by ∼10% per added site with increasing sampling sites per bay, demonstrating fine-scale (<100 km) variation. When we partitioned environmental variability from observed otolith chemistry using predictive models, assignment success improved by 56%, 14%, and 5% for site, bay, and coast, respectively. Our results demonstrate environmental influence on spatial structure of otolith chemistry and illustrate the importance of resolving baseline variability in otolith chemistry when conducting assignment tests. Collectively, our results describe the potential utility of juvenile otolith composition in evaluating contributions of subpopulations to the Northwest Atlantic cod stock and highlight important limitations imposed by environmental variation at scales less than 100 km.

Small-scale temporal and spatial variation in Atlantic cod (Gadus morhua) life history

2003 ◽  
Vol 60 (9) ◽  
pp. 1111-1121 ◽  
Author(s):  
Tara M McIntyre ◽  
Jeffrey A Hutchings
Keyword(s):  
Body Mass ◽  
Life Histories ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Gonadosomatic Index ◽  
Small Scale ◽  
Hepatosomatic Index ◽  
Georges Bank ◽  
High Fecundity

Life histories of Atlantic cod (Gadus morhua) from the Gulf of St. Lawrence south to Georges Bank differ significantly through time and space. Within the Southern Gulf, fecundity per unit body mass differed by more than 40% over short (2 years) and long (42–45 years) periods of time. Significant variation in size-specific fecundity is also evident among populations: Southern Gulf cod produce almost 30% more eggs per unit body mass than those on Georges Bank, whereas fecundity of Scotian Shelf cod is almost half that of cod in Sydney Bight. Compared with those on Georges Bank, Southern Gulf cod life histories are characterized by high fecundity, late maturity, high gonadosomatic index, and large eggs. Relative to the influence of body size, neither temporal nor spatial differences in fecundity can be attributed to physiological condition, as reflected by liver weight, hepatosomatic index, and Fulton's K. Delayed maturity and higher reproductive allotment among Southern Gulf cod can be explained as selection responses to slower growth, higher prereproductive mortality, and fewer lifetime reproductive events. Patterns of covariation in heritable, fitness-related traits suggest the existence of adaptive variation and evolutionarily significant units at spatial scales considerably smaller than the species range in the Northwest Atlantic.

scholarly journals Trade-offs between growth and reproduction in wild Atlantic cod

2014 ◽  
Vol 71 (7) ◽  
pp. 1106-1112 ◽  
Author(s):  
Arild Folkvord ◽  
Christian Jørgensen ◽  
Knut Korsbrekke ◽  
Richard D.M. Nash ◽  
Trygve Nilsen ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Life History Strategy ◽  
Skipped Spawning ◽  
Growth Increments ◽  
Trade Offs ◽  
Survival And Reproduction ◽  
Size At Age ◽  
Allocation Strategies ◽  
Growth And Reproduction

Animals partition and trade off their resources between competing needs such as growth, maintenance, and reproduction. Over a lifetime, allocation strategies should result in distinct trajectories for growth, survival, and reproduction, but such longitudinal individual data are difficult to reconstruct for wild animals and especially marine fish. We were able to reconstruct two of these trajectories in wild-caught Northeast Arctic cod (Gadus morhua) females: size-at-age was back-calculated from otolith growth increments, and recent spawning history was reconstructed from postovulatory follicles and present oocyte development. Our findings indicate distinct trade-offs between length growth and reproduction. Fish that sexually matured early had attained a larger size at age 3 than immatures, but onset of reproduction caused slower growth compared with immatures. We found that 6- and 7-year-old females skipping spawning grew significantly more in the year of missed spawning than females spawning for the second consecutive year. The latter tentatively supports the hypothesis that skipped spawning may occur as an adaptive life-history strategy, given the potential future fecundity gain with increased size.

Assessing the ability of the growing degree-day metric to explain variation in size-at-age and duration-to-moult of lobsters and crabs

2021 ◽  
Author(s):  
Reid William Steele ◽  
Anna B Neuheimer
Keyword(s):  
Growth And Development ◽  
Linear Models ◽  
Growth Models ◽  
Thermal Time ◽  
Individual Growth ◽  
Calendar Time ◽  
Factors Affecting ◽  
Degree Day ◽  
The Individual ◽  
Size At Age

Environmental temperature directly controls the rate at which ectotherms grow and develop. The growing degree-day metric (GDD, °C∙d) scales time by temperature to create a thermal time scale relevant to ectothermic organisms. Here we assess the ability of GDD to model size-at-age and duration-to-moult in 15 datasets (9 size-at-age, 6 duration-to-moult) comprising 7 species of lobsters and crabs. We applied generalized linear models to assess the ability of GDD vs. “calendar” time to explain growth and development observations within and across trials. Best-fit models included GDD with fewer parameters in 6 of 9 size-at-age and 5 of 6 duration-to-moult datasets, and a better fit to the data in 6 of 9 size-at-age datasets. Our results show that the individual growth of lobster and crab species can be modelled using thermal time models. Such models can be used to identify thermal tolerance limits, predict growth under varying temperature conditions and disentangle temperature effects from those of other factors affecting individual growth and development, resulting in improved growth models for field conditions including fisheries management.

Back-Calculated Fish Lengths and Hg and Zn Levels from Recent and 100-Yr-Old Cleithrum Bones from Atlantic Cod (Gadus morhua)

1977 ◽  
Vol 34 (1) ◽  
pp. 147-150 ◽  
Author(s):  
J. S. Scott
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Length ◽  
Zinc Levels

Dimensions of cleithrum bones from recently caught Atlantic cod (Gadus morhua) were measured and plotted against observed fish lengths to back-calculate cod lengths from cleithra from a ship wrecked in 1865. Mercury levels in the historical bones were approximately the same as those in recent material and showed no increase with fish length, but zinc levels appearto have increased since 1865 and increased with fish length.

Factors affecting the swimming endurance and catchability of Atlantic cod (Gadus morhua)

2000 ◽  
Vol 57 (6) ◽  
pp. 1200-1207 ◽  
Author(s):  
Paul D Winger ◽  
Pingguo He ◽  
Stephen J Walsh
Keyword(s):  
Swimming Speed ◽  
Newfoundland And Labrador ◽  
Gadus Morhua ◽  
Failure Time ◽  
Atlantic Cod ◽  
Fish Length ◽  
Time Analysis ◽  
Factors Affecting ◽  
Highly Sensitive ◽  
Swimming Endurance

The swimming endurance of Atlantic cod (Gadus morhua), native to the cold waters off the east coast of Newfoundland and Labrador, was investigated under laboratory conditions. Using a swimming flume, endurance was tested at swimming speeds ranging from 0.6 to 1.3 m·s-1 using water temperatures from 0.0 to 9.8°C ( mean = 3.2°C, SD = 2.8) and fish lengths from 41.0 to 86.0 cm ( mean = 57.8 cm, SD = 10.5). The results revealed that swimming speed was the only significant factor affecting the endurance of cod. The maximum sustained swimming speed (Ums) was predicted to be 0.66 m·s-1. Statistical analysis of the data was conducted using failure time analysis. The hazard, or risk of exhaustion, was found to increase rapidly with increasing swimming speed, i.e., there was a decrease in the probability of cod achieving a given swimming endurance. Probability curves for the endurance of cod were calculated for different swimming speeds. The findings suggest that the catching efficiency of commercially targeted cod (>41.0 cm) by otter trawls may be highly sensitive to changes in towing speed while being independent of both fish length and water temperature.

scholarly journals Evolutionary response to size-selective mortality in an exploited fish population

2007 ◽  
Vol 274 (1613) ◽  
pp. 1015-1022 ◽  
Author(s):  
Douglas P Swain ◽  
Alan F Sinclair ◽  
J Mark Hanson
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Population ◽  
Fish Populations ◽  
Selective Mortality ◽  
Genetic Changes ◽  
Evolutionary Response ◽  
In The Wild ◽  
Size At Age ◽  
Change In Mean

Many collapsed fish populations have failed to recover after a decade or more with little fishing. This may reflect evolutionary change in response to the highly selective mortality imposed by fisheries. Recent experimental work has demonstrated a rapid genetic change in growth rate in response to size-selective harvesting of laboratory fish populations. Here, we use a 30-year time-series of back-calculated lengths-at-age to test for a genetic response to size-selective mortality in the wild in a heavily exploited population of Atlantic cod ( Gadus morhua ). Controlling for the effects of density- and temperature-dependent growth, the change in mean length of 4-year-old cod between offspring and their parental cohorts was positively correlated with the estimated selection differential experienced by the parental cohorts between this age and spawning. This result supports the hypothesis that there have been genetic changes in growth in this population in response to size-selective fishing. Such changes may account for the continued small size-at-age in this population despite good conditions for growth and little fishing for over a decade. This study highlights the need for management regimes that take into account the evolutionary consequences of fishing.

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