Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland

Newly settled age 0 juvenile cod, Atlantic cod Gadus morhua and Greenland cod Gadus ogac, coexist in nearshore areas around Newfoundland, but little is understood on the mechanisms affecting their distribution. In young marine fish, predation risk is often high yet there is generally an increasing c...

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Main Author: Laurel, Benjamin Jeffrey
Format: Thesis
Language:English
Published: Memorial University of Newfoundland 2003
Subjects:
Online Access:https://research.library.mun.ca/10855/
https://research.library.mun.ca/10855/1/Laurel_BenjaminJeffrey.pdf
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spelling ftmemorialuniv:oai:research.library.mun.ca:10855 2023-10-01T03:54:33+02:00 Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland Laurel, Benjamin Jeffrey 2003 application/pdf https://research.library.mun.ca/10855/ https://research.library.mun.ca/10855/1/Laurel_BenjaminJeffrey.pdf en eng Memorial University of Newfoundland https://research.library.mun.ca/10855/1/Laurel_BenjaminJeffrey.pdf Laurel, Benjamin Jeffrey <https://research.library.mun.ca/view/creator_az/Laurel=3ABenjamin_Jeffrey=3A=3A.html> (2003) Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland. thesis_license Thesis NonPeerReviewed 2003 ftmemorialuniv 2023-09-03T06:48:04Z Newly settled age 0 juvenile cod, Atlantic cod Gadus morhua and Greenland cod Gadus ogac, coexist in nearshore areas around Newfoundland, but little is understood on the mechanisms affecting their distribution. In young marine fish, predation risk is often high yet there is generally an increasing capacity in larger individuals to evade predators. It is therefore difficult to distinguish the role of behaviour and differential survival on distribution of fish in their early life stages. In a series of field and laboratory experiments, I investigate how habitat complexity, predators and conspecific density interact to affect survival and behaviour in juvenile cod, and ultimately, their distribution in coastal Newfoundland. -- In a bay-scale study (~10 km²), I monitored patterns of settlement and distribution of G. morhua and G. ogac, following a large-scale alteration of nearshore eelgrass (Zostera marina) habitat. Comparisons of bi-weekly sampling between control and experimental sites from 1995-2001 indicated a significant increase in cod abundance at sites enhanced with simulated eelgrass and a corresponding decrease in cod numbers at sites where eelgrass had been removed. These data supported predictions, demonstrating that: 1) there was a sufficient supply of juvenile cod within the range of areas that have historically been unoccupied (i.e. sand) and 2) both species preferred to settle in complex habitats. However, G. ogac responded significantly to the removal of eelgrass in more comparisons than G. morhua (70% and 37% respectively), suggesting that G. ogac have a higher affinity for complex vegetative habitats than G. morhua at the scale of manipulation (ca. 800m²). Furthermore, despite an overall preference for eelgrass habitat, high within-site catch variation indicated that individuals of both species were not restricted to any single seine site. Rather, the highly variable data indicate that juvenile cod were mobile and occasionally aggregated throughout the study period. My results support previously ... Thesis atlantic cod Gadus morhua Gadus ogac Greenland Greenland cod Newfoundland Memorial University of Newfoundland: Research Repository Greenland
institution Open Polar
collection Memorial University of Newfoundland: Research Repository
op_collection_id ftmemorialuniv
language English
description Newly settled age 0 juvenile cod, Atlantic cod Gadus morhua and Greenland cod Gadus ogac, coexist in nearshore areas around Newfoundland, but little is understood on the mechanisms affecting their distribution. In young marine fish, predation risk is often high yet there is generally an increasing capacity in larger individuals to evade predators. It is therefore difficult to distinguish the role of behaviour and differential survival on distribution of fish in their early life stages. In a series of field and laboratory experiments, I investigate how habitat complexity, predators and conspecific density interact to affect survival and behaviour in juvenile cod, and ultimately, their distribution in coastal Newfoundland. -- In a bay-scale study (~10 km²), I monitored patterns of settlement and distribution of G. morhua and G. ogac, following a large-scale alteration of nearshore eelgrass (Zostera marina) habitat. Comparisons of bi-weekly sampling between control and experimental sites from 1995-2001 indicated a significant increase in cod abundance at sites enhanced with simulated eelgrass and a corresponding decrease in cod numbers at sites where eelgrass had been removed. These data supported predictions, demonstrating that: 1) there was a sufficient supply of juvenile cod within the range of areas that have historically been unoccupied (i.e. sand) and 2) both species preferred to settle in complex habitats. However, G. ogac responded significantly to the removal of eelgrass in more comparisons than G. morhua (70% and 37% respectively), suggesting that G. ogac have a higher affinity for complex vegetative habitats than G. morhua at the scale of manipulation (ca. 800m²). Furthermore, despite an overall preference for eelgrass habitat, high within-site catch variation indicated that individuals of both species were not restricted to any single seine site. Rather, the highly variable data indicate that juvenile cod were mobile and occasionally aggregated throughout the study period. My results support previously ...
format Thesis
author Laurel, Benjamin Jeffrey
spellingShingle Laurel, Benjamin Jeffrey
Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland
author_facet Laurel, Benjamin Jeffrey
author_sort Laurel, Benjamin Jeffrey
title Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland
title_short Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland
title_full Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland
title_fullStr Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland
title_full_unstemmed Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland
title_sort interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (gadus spp.) in newfoundland
publisher Memorial University of Newfoundland
publishDate 2003
url https://research.library.mun.ca/10855/
https://research.library.mun.ca/10855/1/Laurel_BenjaminJeffrey.pdf
geographic Greenland
geographic_facet Greenland
genre atlantic cod
Gadus morhua
Gadus ogac
Greenland
Greenland cod
Newfoundland
genre_facet atlantic cod
Gadus morhua
Gadus ogac
Greenland
Greenland cod
Newfoundland
op_relation https://research.library.mun.ca/10855/1/Laurel_BenjaminJeffrey.pdf
Laurel, Benjamin Jeffrey <https://research.library.mun.ca/view/creator_az/Laurel=3ABenjamin_Jeffrey=3A=3A.html> (2003) Interactions of predators, habitat and conspecifics on the coastal distribution of age 0 juvenile cod (Gadus spp.) in Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland.
op_rights thesis_license
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