Greenland Cod Gadus Ogac Research Articles

Examination of fine‐scale spatial‐temporal overlap and segregation between two closely related congeners Gadus morhua and Gadus ogac in coastal Newfoundland

The spatial and temporal movement patterns of sympatric juvenile Atlantic cod Gadus morhua and Greenland cod Gadus ogac were studied using high-resolution radio-acoustic positioning in a coastal area of Newfoundland during the summers of 2009 and 2010. A total of 20 fish (10 G. ogac and 10 G. morhua) were equipped with acoustic transmitters and monitored for periods up to 23 days. Most fishes showed high site fidelity with mean residence times of 12·4 (G. morhua) and 14·4 days (G. ogac). A few individuals showed a transient use of the study area, ranging distances up to c. 4 km. Mean daily home ranges [95% kernel utilization distributions (KUDs)] and core activity areas were significantly larger for G. morhua (3·8 and 0·5 ha) than for G. ogac (2·7 and 0·3 ha). Home ranges were not related to total length (LT ) for G. morhua but showed a weak positive relationship for G. ogac. Gadus morhua occupied larger areas during the day while G. ogac occupied slightly larger areas at night. Mean rates of movement for G. ogac and G. morhua ranged from 0·83 to 1·24 and 0·76 to 1·76 LT s(-1) , respectively, and were highest during crepuscular periods. Overall, G. morhua were wider ranging, moved at faster rates and were active throughout the diel cycle compared to G. ogac of the same size. It is suggested that differential use of space and activity periods plays an important role in the successful coexistence of these two species.

Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod Gadus ogac in a Newfoundland fjord

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 503:235-246 (2014) - DOI: https://doi.org/10.3354/meps10729 Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod Gadus ogac in a Newfoundland fjord Melanie Shapiera1,*, Robert S. Gregory2, Corey J. Morris2, Curtis J. Pennell2, Paul V. R. Snelgrove1 1Department of Biology and Ocean Sciences Centre, Memorial University of Newfoundland, St. John’s, Newfoundland A1C 5S7, Canada 2Fisheries and Oceans Canada, Ecological Sciences Section, 80 East White Hills Road, PO Box 5667, St. John’s, Newfoundland A1C 5X1, Canada *Corresponding author: m.shapiera22@gmail.com ABSTRACT: We used acoustic telemetry to track age 1 juvenile Greenland cod Gadus ogac in Newman Sound, Newfoundland, from October 2010 to November 2012, in 2 consecutive 1 yr experiments. Using single (Year 1) and reciprocal (Year 2) transplant study designs, we investigated seasonal dispersal, home range area, and potential homing behaviour between coves ~3.5 km apart. We tracked individuals moving at metre to kilometre scales, using a network of 26 to 32 hydrophones. We converted tag detections to position estimates in order to calculate seasonal home ranges and individual movement patterns. Home range increased significantly with season (pre-winter, winter, and post-winter) in both study years. Mean seasonal home range area ranged from 0.29 to 3.47 km2 in Year 1 and 0.43 to 1.72 km2 in Year 2. In contrast, fish size-at-capture, capture location, and release location had no significant effect on seasonal home range. Increased movement distance during the winter and post-winter season suggests a reduction in predation pressure on age 1 juveniles at these times, challenging previous assumptions about their vulnerability. We observed variable behaviour spanning residency to kilometre-scale dispersal movements, which represent greater distances than previously assumed. Similar proportions of control and transplant fish visited the other cove, indicating an absence of homing behaviour among dispersing individuals. Juveniles of marine fishes are often characterized as key life history transition stages between vulnerable larvae and older, larger individuals which are less susceptible to predators. Our results indicate that early juvenile life stages may be substantially more mobile than presupposed and contribute to population connectivity in temperate fishes in ways not well described previously. KEY WORDS: Home range · Telemetry · Gadus ogac · Dispersal · Juvenile · Site fidelity Full text in pdf format PreviousNextCite this article as: Shapiera M, Gregory RS, Morris CJ, Pennell CJ, Snelgrove PVR (2014) Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod Gadus ogac in a Newfoundland fjord. Mar Ecol Prog Ser 503:235-246. https://doi.org/10.3354/meps10729 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 503. Online publication date: April 29, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Variability of microsatellite loci of Greenland cod Gadus ogac Richardson 1836: Comparison with other species of Gadus genus (Gadidae)

Comparative analysis of variability of seven microsatellite loci—Gmo3, Gmo-G12, Gmo-G18, Gmo19, Gmo34, Gmo35 and Pgmo32—was performed for the Greenland cod Gadus ogac, Pacific cod G. macrocephalus, Atlantic cod G. morhua, and White Sea cod G. morhua marisalbi. High genetic identity was observed between the Greenland cod and Pacific cod (I = 0.9520). Pair analysis of genetic differentiation was performed on the studied microsatellite loci according to θ (analogue of F ST). The Greenland cod differed significantly from the Pacific, Atlantic, and the White Sea cod; however, the differentiation level varied. The lowest value was observed for the pair Greenland cod-Pacific cod (0.123), and the highest levels were registered for the pairs Greenland cod-Atlantic cod (0.605) and Greenland cod-White Sea cod (0.535).

Behavioural consequences of density-dependent habitat use in juvenile cod Gadus morhua and G. ogac: the role of movement and aggregation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 272:257-270 (2004) - doi:10.3354/meps272257 Behavioural consequences of density-dependent habitat use in juvenile cod Gadus morhua and G. ogac: the role of movement and aggregation B. J. Laurel1,*, R. S. Gregory1,2, J. A. Brown1, J. K. Hancock1, D. C. Schneider1 1Memorial University of Newfoundland, Ocean Sciences Centre, St. John¹s, Newfoundland A1C 5S7, Canada 2Department of Fisheries and Oceans, St. John¹s, Newfoundland A1C 5X1, Canada *Email: blaurel@mun.ca ABSTRACT: Fish behaviour can change to accommodate a variable environment, but changes in behaviour have not been considered in the context of density-dependent habitat use. In Bonavista Bay, Newfoundland, we measured how fish density movement and schooling behaviour changed with habitat in 2 gadids, Atlantic cod Gadus morhua and Greenland cod Gadus ogac, using a combination of field-seines, mark-recapture and laboratory experiments. Density estimates from seines (n = 427) over 5 yr (1996, 1998 to 2001) indicated that these species associated with eelgrass but periodically were detected in high abundance over unvegetated habitat (i.e. sand). Within-site catch variation indicated both species aggregated more in sand than eelgrass habitat, and, in Atlantic cod, aggregations over sand increased as density in eelgrass increased. Although such patterns in catch data could be interpreted as due to the effects of differential mortality between habitats, a mark-recapture experiment indicated that both species of cod were not site-attached and moved between seine locations. Furthermore, video-analysis from laboratory experiments demonstrated that cod formed tighter aggregations over sand compared to eelgrass habitats. Our results suggest that juvenile cod modify their behaviour with changing density, possibly as a means of exploiting poor-quality habitats when high-quality habitats are saturated with conspecifics. Consequently, habitat suitability for Atlantic cod may be a dynamic rather than fixed variable in density-dependent habitat models. KEY WORDS: Density-dependence · Habitat selection · Atlantic cod · Greenland cod · Aggregation · Shoaling Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 272. Online publication date: May 19, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.