Regulation of infrapopulations of Cryptocotyle lingua on cod
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Abstract:
To study the infection dynamics of metacercariae of the digenean Cryptocotyle lingua , wild living Atlantic cod, Gadus morhua , were caged for 18 months close to the shore. Here they were exposed to naturally occurring transmission stages of the parasite. First, both the abundance and the variance to mean ratio of metacercariae increased, but during the second half of the study the abundance levelled out, and the variance to mean ratio showed a significant decrease. Host mortality was negligible throughout the study. Based on the relationship between pigment spots and metacercariae observed by skin digestion, there was no indication of density-dependent parasite mortality. We conclude that the infrapopulations of metacercariae on the caged cod probably were regulated by density-dependent host responses acting against the cercariae.Keywords:
Gadidae
Density dependence
The gadoid fishes, including the Atlantic cod and haddock, are currently being exploited close to their safe biological limits, requiring restrictions upon the human activities that may harm them. This has prompted interest in the biology of such fishes. Studies of the cod and haddock have shown highly complex behavior, involving prolonged and energetic visual and acoustic displays. Different sounds are produced in different behavioral contexts and are emitted almost continuously by cod and haddock, especially throughout the spawning season (February to May). The distinctive characteristics of these sounds make it possible to locate spawning cod and haddock at their marine spawning grounds. Human activities in these areas may affect their spawning adversely and have deleterious effects upon their stocks. Man-made sounds in water do have an adverse effect upon cod and haddock, and other fishes. Listening for the cod and haddock sounds provides a reliable, non-invasive technique for detecting their locations, and especially their spawning areas, and enables them to be protected well.
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Gadidae
Swim bladder
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Gadidae
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Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) are two commercially important marine fishes impacted by both overfishing and climate change. Increasing ocean temperatures are affecting the physiology of these species and causing changes in distribution, growth, and maturity. While the physiology of cod has been well investigated, that of haddock has received very little attention. Here, we measured the metabolic response to increasing temperatures, as well as the critical thermal maximum (CTmax), of cod acclimated to 8 and 12 °C and haddock acclimated to 12 °C. We also compared the swimming performance (critical swimming speed, Ucrit) of cod and haddock at 12 °C, as well as the Ucrit of 12 °C-acclimated cod acutely exposed to a higher-than-optimal temperature (16 °C). The CTmax for cod was 21.4 and 23.0 °C for 8- and 12 °C-acclimated fish, respectively, whereas that for the 12 °C-acclimated haddock was 23.9 °C. These values were all significantly different and show that haddock are more tolerant of high temperatures. The aerobic maximum metabolic rate (MMR) of swimming cod remained high at 16 °C, suggesting that maximum oxygen transport capacity was not limited at a temperature above optimal in this species. However, signs of impaired swimming (struggling) were becoming evident at 16 °C. Haddock were found to reach a higher Ucrit than cod at 12 °C (3.02 vs. 2.62 body lengths s-1, respectively), and at a lower MMR. Taken together, these results suggest that haddock perform better than cod in warmer conditions, and that haddock are the superior swimmer amongst the two species.
Haddock
Gadidae
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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.
Gadidae
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Gadidae
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The immunoglobulin (Ig) level in serum from Atlantic cod, Gudus morhua L. (Teleostomi, Gadiformes), was measured using ELISA. Cod serum contains 5.62 ± 0.19 mg Ig ml, which constitute 17.2% of the total serum proteins. Polyclonal and monoclonal antibodies (Ab) against cod‐Ig were used for cross‐reactivity studies in sera from other species. The cross‐reaction with polyclonal Ab was high in gadifom fish, and low or absent in the other tested species. Immunoprecipitation showed that the Ab only binds to the Ig of the serum from the other species. The results within the gadiform group indicate that (1) Gadidae and Lotidae are more closely related to each other than to Merluccidae, (2) Phycidae is more distant related to Lotidae than earlier considered, (3) Zoarcidae seem to be more distant related to Gadus than other species of Gadiformes. These results support recent revisions of the systematics of Gadiformes. Monoclonal Ab against the heavy chain of cod‐Ig show no, or small (< 15%) cross‐reactions with serum from gadiform species. One monoclonal Ab against the light chain shows high cross‐reaction and also binds to Ig from species outside the Gadiformes, indicating that the light chain of Ig might be more conserved than the heavy chain.
Polyclonal antibodies
Gadidae
Cross-reactivity
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Gadidae
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Haddock
Gadidae
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Gadidae
Haddock
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