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 Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys

2009 ◽  
Vol 66 (6) ◽  
pp. 1225-1232 ◽  
Author(s):  
Viacheslav A. Ermolchev
Keyword(s):  
Gadus Morhua ◽  
Barents Sea ◽  
Atlantic Cod ◽  
Biological Data ◽  
Target Strength ◽  
Fish Length ◽  
The Barents Sea ◽  
Total Fish ◽  
Acoustic Surveys

Abstract Ermolchev, V. A., 2009. Methods and results of in situ target-strength measurements of Atlantic cod (Gadus morhua) during combined trawl-acoustic surveys. – ICES Journal of Marine Science, 66: 1225–1232. This paper presents methods for collecting acoustic and biological data, including in situ target-strength (TS) estimates of fish, with results presented for Atlantic cod (Gadus morhua) obtained from combined trawl-acoustic surveys. These include fish in the small, average, and maximum length classes, within the range 5–136 cm (total fish length, LT). The investigations were done using Simrad EK500/EK60 echosounders with split-beam transducers and special post-processing software. Based on an analysis of data collected in the Barents Sea during 1998–2007, a relationship TS = 25.2 log10(LT) − 74.8 was obtained for Atlantic cod at 38 kHz, with TS in dB and LT in centimetres. Seasonally, and for depths between 50 and 500 m, the variability in cod TS was 3.1 dB, decreasing with depth. The largest day–night difference in mean TS was in August–September, with changes as large as 1.0–1.7 dB. In the other seasons, the day–night difference was <1.0 dB.

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.

Larval Fish Age, Growth, and Body Shrinkage: Information Available from Otoliths

1989 ◽  
Vol 46 (11) ◽  
pp. 1884-1894 ◽  
Author(s):  
Richard L. Radtke
Keyword(s):  
Growth Rate ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Larval Fish ◽  
Quadratic Function ◽  
Age And Growth ◽  
Fish Length ◽  
Elapsed Time ◽  
Developmental Rates ◽  
The Relationship

External and internal examination of Atlantic cod (Gadus morhua) otoliths for macrostructure and microstructure, by light and scanning electron microscopy, indicated daily rhythmic patterns. The first daily increment developed the day after hatching. Sagittae changed shape from spherical to oblong at 20 d and to crenulated at 50−60 d old. Cod were reared at three temperatures (6,8 and 10 °C), to provide a range of growth and developmental rates. Distinctive marks formed at yolk-sac absorption, initiation of feeding and settlement. It was possible to determine age and growth rate from otolith analyses. The relationship between otolith length and fish size was independent of growth rate; it followed a quadratic function for the smaller individuals (< 6.5 mm), and it was linear in individuals greater than 25 mm. Larval fish shrank considerably at death. The magnitude of shrinkage was dependent on larval length, and the elapsed time between death and fixation. Immediate fixation in ethanol resulted in minimal shrinkage. The relationship between fish length and otolith diameter may be used to correct for shrinkage associated with collection and death.

Antifreeze Production, Freeze Resistance, and Overwintering of Juvenile Northern Atlantic Cod (Gadus morhua)

1992 ◽  
Vol 49 (3) ◽  
pp. 516-522 ◽  
Author(s):  
Sally V. Goddard ◽  
Ming H. Kao ◽  
Garth L. Fletcher
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Length ◽  
Antifreeze Glycoproteins ◽  
Freeze Resistance ◽  
Ambient Temperatures ◽  
Temperature Regimes ◽  
Northern Atlantic ◽  
Freezing Temperatures ◽  
Cycling Temperature

Four size groups of northern Atlantic cod (Gadus morhua) (juveniles < 15, 15–25, and 26–40 cm and adults > 50 cm) were investigated over a winter cycle for their ability to increase freeze resistance by producing plasma antifreeze glycoproteins. All juveniles had significantly higher plasma antifreeze levels than adults during the winter (January–March) under similar conditions of cycling temperature and ambient photoperiod. Highest winter plasma antifreeze levels and lowest plasma freezing temperatures were consistently found in the 15–25 cm group. Fish length and plasma antifreeze levels were inversely related from January to April, with the exception of the 0 + cod. All juvenile groups developed considerable freeze protection early in the winter cycle before the onset of freezing temperatures. However, the adults were not significantly protected until the end of January, when ambient temperatures had fallen below 0 °C. The 15–25 cm cod were held in three cycling temperature regimes. Induction temperatures for antifreeze production in this size group appeared to be between 2 and 3 °C, as compared with between 1 and 0 °C for the adults. We suggest that these patterns of antifreeze production may have direct bearing on habitat selection and overwintering behaviour of the northern Atlantic cod at different stages of development.

Distribution of gill parasite (Lernaeocera branchialis) infection in Northwest Atlantic cod (Gadus morhua) and parasite-induced host mortality: inferences from tagging data

1998 ◽  
Vol 55 (2) ◽  
pp. 364-375 ◽  
Author(s):  
Megan EB Jones ◽  
Christopher T Taggart
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Negative Relationship ◽  
Parasite Prevalence ◽  
Geographic Region ◽  
Fish Length ◽  
Differential Survival ◽  
Northwest Atlantic ◽  
Gill Parasite ◽  
In The Wild

We describe geographic and host size related trends in the prevalence of the gill parasite Lernaeocera branchialis (Copepoda, Pennellidae) infecting Atlantic cod (Gadus morhua) in coastal Newfoundland and Labrador and assess the effect of parasitism on cod survival in the wild. Using cod-tagging studies conducted between 1962 and 1989, we test three null hypotheses: (1) parasite prevalence in the Northwest Atlantic is latitudinally invariant, (2) infected cod have the same survival probability as parasite-free cod, and (3) parasite prevalence is independent of fish length. The first hypothesis is rejected given a significantly negative relationship between prevalence and latitude. The second hypothesis is rejected in one geographic region where 8% fewer infected cod from northeast Newfoundland were recaptured relative to uninfected cod. This implies that parasitized cod can suffer an 8% differentially higher mortality relative to nonparasitized cod. The third hypothesis is rejected because the proportion of cod infected was generally greatest in the 43-49 cm length-class and decreased significantly with increasing length. Differential survival between infected and uninfected cod within length-classes was not observed. The use of L. branchialis as a population marker warrants caution. The parasite has the potential to affect the recovery of depleted Northwest Atlantic cod stocks in a geographically differential manner.

Otolith Elemental Fingerprinting for Stock Identification of Atlantic Cod (Gadus morhua) Using Laser Ablation ICPMS

1994 ◽  
Vol 51 (9) ◽  
pp. 1942-1950 ◽  
Author(s):  
Steven E. Campana ◽  
Anthony J. Fowler ◽  
Cynthia M. Jones
Keyword(s):  
Laser Ablation ◽  
Trace Element ◽  
Inductively Coupled Plasma ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Length ◽  
Stock Identification ◽  
Inductively Coupled ◽  
Elemental Fingerprint ◽  
Elemental Fingerprinting

Trace element incorporation into fish otoliths varies among samples collected at different sites. If otolith elemental composition (the elemental "fingerprint") somehow reflects the characteristics of the ambient water, the elemental fingerprint of the otolith nucleus could serve as a natural marker of fish hatched at different sites. To test this hypothesis, Atlantic cod (Gadus morhua) otoliths collected from five spawning grounds in the northwest Atlantic were tested for differences in elemental and isotopic composition. Laser ablation – inductively coupled plasma mass spectroscopy (LA-ICPMS) was used to assay the concentration of 14 isotopes (nine elements) in otolith nuclei. The sensitivity of the laser ablation system exceeded that of the electron microprobe by 2–4 orders of magnitude, with an average CV of 21% for any given isotope. Most isotopic concentrations were consistent between left and right otoliths of a given fish, and most differed significantly among sample sites; there were no significant differences by age, sex, or fish length. Multivariate analyses of the elemental fingerprints resulted in significant discrimination among sample sites. While the mechanism underlying trace element incorporation into otoliths is still unclear, otolith elemental fingerprinting has the potential to become an effective and accurate means of stock identification.

Back-calculation of previous fish size using individually tagged and marked Atlantic cod (Gadus morhua)

2008 ◽  
Vol 65 (11) ◽  
pp. 2496-2508 ◽  
Author(s):  
L. Li ◽  
H. Høie ◽  
A. J. Geffen ◽  
E. Heegaard ◽  
J. Skadal ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Time Interval ◽  
Fish Length ◽  
Food Regimes ◽  
Back Calculation ◽  
Width Measurements ◽  
Nonlinear Scale ◽  
Marking Time ◽  
Selection Of

The performance of five back-calculation (B-C) models was tested with individually tagged and multiple alizarin-marked Atlantic cod ( Gadus morhua ) reared at seasonally varying water temperature and food regimes over a 10-month period. The otoliths were transversely sectioned and the otolith growth between marks was measured along the dorsal, distal, and ventral radii and across the otolith width. Observed fish lengths at each marking time were compared with back-calculated lengths using linear and nonlinear scale and body proportional hypotheses (SPH and BPH) and biological intercept (BI) models. Measurements along the dorsal and distal radius with SPH and BI provided more accurate fish length estimates but with lower precision, whereas measurements of the ventral radius consistently produced greater overestimations by any model. Otolith width measurements produced moderately overestimated fish length estimates but with the highest precision and were significantly affected by temperature in all models. Certain combinations of model and otolith dimension were more sensitive to the length of the back-calculation time interval, whereas varying feeding regime induced temporary biases only. The selection of B-C model and otolith dimension thus depends not only on the environmental conditions that the fish experience, but also on the requirements of the application for which the B-C is used.

Settlement processes induce differences in daily growth rates between two co-existing ecotypes of juvenile cod Gadus morhua

2020 ◽  
Vol 650 ◽  
pp. 175-189 ◽  
Author(s):  
KEM Jørgensen ◽  
AB Neuheimer ◽  
PE Jorde ◽  
H Knutsen ◽  
P Grønkjær
Keyword(s):  
North Sea ◽  
Growth Rates ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Life Stage ◽  
Fish Length ◽  
Daily Growth ◽  
The North ◽  
Significant Difference ◽  
The North Sea

Co-existence of sympatric populations of a fish species is a common phenomenon. In the fjords of southern Norway, 2 ecotypes of Atlantic cod Gadus morhua co-exist during their juvenile life stage. Cod of the North Sea ecotype are on average 2 cm larger than the fjord ecotype at the end of their first growing season in October, suggesting either differences in spawning time or differences in growth during the larval and early juvenile phase. We analysed 24352 daily otolith increments from 145 cod sampled in September 2000, 2003, 2008 and 2015 at 2 locations to estimate individual hatching times and daily growth rates. There was no significant difference in hatching time between ecotypes, locations or years. Population-specific models of the effect of year, temperature and fish length on growth rates showed that the North Sea ecotype grew significantly faster than the fjord ecotype, but growth rate differences were small until the juveniles reached ~40 mm and disappeared again in juveniles larger than 110 mm. The size range (40-110 mm) corresponds to the period following settling. This study documents how vital rates (e.g. growth rates) may change rapidly at ontogenetic transition points, leading to different phenotypic trajectories in co-existing ecotypes. It also highlights the importance of settlement as a key life-history transition that may amplify small existing differences in growth rates through positive feedback of size on competitive ability and eventually recruitment.

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