The reproductive cycle of male Atlantic cod (Gadus morhua L.) from Placentia Bay, Newfoundland

2000 ◽  
Vol 78 (6) ◽  
pp. 1017-1025 ◽  
Author(s):  
Rick M. Rideout ◽  
Margaret P.M. Burton
Keyword(s):  
Reproductive Cycle ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Placentia Bay

The reproductive cycle of male Atlantic cod (Gadus morhua L.) from Placentia Bay, Newfoundland

2000 ◽  
Vol 78 (6) ◽  
pp. 1017-1025 ◽  
Author(s):  
Rick M Rideout ◽  
Margaret PM Burton
Keyword(s):  
Reproductive Cycle ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Rapid Development ◽  
Liver Lipid ◽  
Gonad Development ◽  
Feeding Intensity ◽  
Gonad Mass ◽  
Gonad Size ◽  
Placentia Bay

The timing of the reproductive cycle of male Atlantic cod (Gadus morhua L.) from Placentia Bay, Newfoundland, was determined from histological gonad samples collected throughout the year. Cycles in gonad mass, whole mass, and somatic mass indices were also determined. Results were consistent with a spring spawning population, with males having testes filled with spermatozoa as early as January. There was a short resting period following spermiation, during which residual sperm was resorbed, followed by rapid development so that some sperm was again evident in the testes as early as November. At first, the presence of spermatozoa was accompanied by cells in all other stages of development, but by spermiation the testes were filled mostly with spermatozoa. Gonad size was largest in April, smallest in October, and increased steeply again in November. Energy for gonad growth came from food intake, as well as liver lipid stores. Gonad development was, for the most part, finished prior to the winter reduction in feeding intensity.

scholarly journals Otolith chemistry and redistributions of Northern cod: evidence of Smith Sound – Bonavista Corridor connectivity

2018 ◽  
Vol 75 (12) ◽  
pp. 2302-2312 ◽  
Author(s):  
Victoria Neville ◽  
George Rose ◽  
Sherrylynn Rowe ◽  
Robyn Jamieson ◽  
Glenn Piercey
Keyword(s):  
Oxygen Isotope ◽  
Gadus Morhua ◽  
Direct Evidence ◽  
Atlantic Cod ◽  
Otolith Chemistry ◽  
Stable Oxygen Isotope ◽  
Metapopulation Structure ◽  
Northern Cod ◽  
Stable Oxygen ◽  
Placentia Bay

Stable oxygen isotope assays of otoliths (δ18Ooto) from migrant Atlantic cod (Gadus morhua Linnaeus, 1758) that overwintered in Smith Sound, Newfoundland, during 1995–2006 differed from those of nonmigrating summer residents and cod from Placentia Bay and Halibut Channel but did not differ from those of cod from the adjacent offshore Bonavista Corridor in summer. All fish sampled were of the 1990 year class (founder of the Smith Sound aggregation) at ages 8–10 years. Hence, overwintering Smith Sound and summering Bonavista Corridor cod likely experienced similar temperatures and salinities in each year of life, representing different migration stages of an intermixed group. Moreover, predictions of δ18Ooto from near-bottom ocean temperatures and salinities differed between inshore and offshore sites and, in general, matched observed signatures of inshore and offshore cod. The Bonavista Corridor cod, however, were an exception, having δ18Ooto signatures suggestive of inshore exposure. Our findings provide direct evidence of metapopulation structure in the Northern cod and are consistent with offshore rebuilding having been spurred by dispersal of cod from inshore Smith Sound.

Small-scale spatial and temporal patterns in spawning of Atlantic cod (Gadus morhua) in coastal Newfoundland waters

2000 ◽  
Vol 57 (5) ◽  
pp. 1011-1024 ◽  
Author(s):  
Gareth L Lawson ◽  
George A Rose
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Temporal Patterns ◽  
Small Scale ◽  
Spatial And Temporal Patterns ◽  
Spawning Grounds ◽  
Acoustic Surveys ◽  
Placentia Bay ◽  
June July ◽  
Timing Of Spawning

Acoustic surveys were used to locate coastal Atlantic cod (Gadus morhua) spawning grounds and examine spatial and temporal patterns of spawning in Placentia Bay, Newfoundland, Canada. The same three grounds were used in 1997 and 1998 (Bar Haven in the inner bay and Cape St. Mary's and Oderin Bank in the outer bay). Grounds had densities >0.1 fish·m-2 over scales of 100 m and >13% of mature females in spawning condition. Ground use and spawning timing differed between years. Mean spawning female densities were highest at Cape St. Mary's in 1997 (1.6 × 10-2 fish·m-2) and Oderin Bank in 1998 (1.0 × 10-2 fish·m-2). At all grounds, spawning peaked earlier in 1997 (April) than in 1998 (June-July). In both years, cod spawned at sub- or near-zero temperatures. "Spawning columns" were observed at sites and times having high densities of spawning females. Sex ratios suggested that males arrived first and stayed later, while females followed when ready to spawn, accompanied by juveniles. Older females spawned earlier and later than younger females. Peaks in density of spawning females and the proportion of females spawning did not coincide. Hence, the location and timing of spawning cannot be quantified solely from the proportions of females in spawning condition.

Peculiarities in ovarian structure leading to multiple-year delays in oogenesis and possible senescence in Atlantic cod, Gadus morhua L.

2000 ◽  
Vol 78 (10) ◽  
pp. 1840-1844 ◽  
Author(s):  
Rick M Rideout ◽  
Margaret PM Burton
Keyword(s):  
Atlantic Ocean ◽  
Reproductive Cycle ◽  
Gadus Morhua ◽  
East Coast ◽  
Atlantic Cod ◽  
Spawning Season ◽  
Northwest Atlantic ◽  
Spawning Cycle ◽  
Ovarian Structure

Five specimens of female Atlantic cod, Gadus morhua L., four collected during regular surveys of the northwest Atlantic Ocean, had ovarian structures that suggested that multiple-year interruptions were occurring in the spawning cycle of these fish. One specimen was experiencing a minimal 2-year delay in its reproductive cycle because the ovary contained only oogonia, which would have had to mature before any spawning could occur. Two other specimens did not contain oogonia or perinucleolar-stage oocytes, suggesting that these ovaries were senescent. Another two ovaries, one removed from a broodstock female and one taken from a female collected off Newfoundland's east coast, contained large masses of resorbing hyaline oocytes, which would likely have impaired the normal release of hydrated oocytes in the next spawning season.

Multiyear homing of Atlantic cod to a spawning ground

2001 ◽  
Vol 58 (12) ◽  
pp. 2325-2329 ◽  
Author(s):  
D Robichaud ◽  
G A Rose
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spawning Season ◽  
Spawning Ground ◽  
Long Distance ◽  
Tag Loss ◽  
Sea Bed ◽  
Placentia Bay

Long-term sonar transmitting tags were implanted in 27 female and 21 male cod (Gadus morhua) at the Bar Haven spawning ground in Placentia Bay, Newfoundland, in April 1998. Two thirds of tagged fish were relocated. All relocations during the 1999 and 2000 spawning seasons were within 10 km of the tagging site, the majority being within a few hundred metres. No tagged fish were relocated at other spawning grounds or elsewhere in the bay during the spawning season. Outside the spawning season, several tagged fish were relocated in other parts of the bay at ranges of a few kilometres to 110 km from the tagging site, as were 13 of 15 fishery returns (2 returns from several hundred kilometres outside the bay). Homing rates in 1999 and 2000 were 39% and 53%, respectively, after adjustments for tag loss, mortality, misreporting, and relocation efficiency based on returns from a sea-bed beacon tag left at the Bar Haven grounds. Multiyear homing was observed in 26% of cod. This study provides the first direct evidence that cod undertaking long-distance feeding migrations may home to a specific spawning ground in consecutive years, and a hypothesis for the slow recolonisation rates observed in North Atlantic cod stocks.

scholarly journals Passive- and active-acoustic properties of a spawning Atlantic cod (Gadus morhua) aggregation

2009 ◽  
Vol 66 (6) ◽  
pp. 1259-1263 ◽  
Author(s):  
Susan B. Fudge ◽  
George A. Rose
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Sea Surface ◽  
Acoustic Properties ◽  
Marine Science ◽  
Spawning Aggregation ◽  
Acoustic Sensors ◽  
Migratory Behaviour ◽  
Night Time ◽  
Placentia Bay

Abstract Fudge, S. B., and Rose, G. A. 2009. Passive- and active-acoustic properties of a spawning Atlantic cod (Gadus morhua) aggregation. – ICES Journal of Marine Science, 66: 1259–1263. A spawning aggregation of Atlantic cod (Gadus morhua) was observed at depths of 40–50 m with passive- and active-acoustic sensors at the Bar Haven grounds in Placentia Bay, Newfoundland, in April 2003. A hydrophone was positioned on the seabed beneath the aggregation, while a 38-kHz split-beam echosounder was moored at the sea surface above it for 18.5 h. Ten grunts were recorded with peak frequencies ranging from 30 to 250 Hz and durations of nearly 300 ms. These grunts are similar to the sounds recorded in the presence of captive, spawning cod from the same substock. The echogram reveals that cod exhibit diel, vertical-migratory behaviour, densely aggregating near the seabed by day and forming columns that extend approximately halfway to the surface at night. This is the first study to demonstrate that cod produce sounds and form columns while migrating vertically during night-time spawning.

scholarly journals Density-dependent distribution of demersal juvenile Atlantic cod (Gadus morhua) in Placentia Bay, Newfoundland

2006 ◽  
Vol 63 (4) ◽  
pp. 766-774 ◽  
Author(s):  
David Robichaud ◽  
George A. Rose
Keyword(s):  
Spatial Patterns ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fish Size ◽  
Density Dependent ◽  
Placentia Bay ◽  
Western Side ◽  
Catch Rates ◽  
Single Cohort

Abstract Age 0 cod (Gadus morhua) were surveyed with beach-seines monthly from September to December, 1997–1999, at sites located throughout Placentia Bay, Newfoundland. Catch rates (densities) varied annually, being highest in 1998 (7 fish per sample) and lowest in 1997 (<1). Each year, fish size and density increased from September to November, as expected from a stock that tends to produce a single cohort spawned in April/May. However, in December the expected larger fish were absent, and the presence of smaller cod suggested a later cohort (July spawning). Large-scale spatial patterns also persisted among years, with densities consistently higher in the inner bay and on the western side, and lower on the eastern side. The rank of the sites from greatest to lowest density of age 0 cod remained fairly consistent among years. In a comparison of all 12 sampling events, the proportion of sites occupied by cod was strongly and positively correlated with the total number caught (r2 = 0.95). These observations suggested a density-dependent range expansion not previously reported for age 0 cod.

Transport and development of eggs and larvae of Atlantic cod, Gadus morhua, in relation to spawning time and location in coastal Newfoundland

2000 ◽  
Vol 57 (9) ◽  
pp. 1761-1772 ◽  
Author(s):  
Ian R Bradbury ◽  
Paul V.R. Snelgrove ◽  
Sandra Fraser
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Early Spring ◽  
Egg Hatching ◽  
Larval Size ◽  
Order Of Magnitude ◽  
Larval Production ◽  
Placentia Bay ◽  
Eggs And Larvae

We provide evidence that variation in location and timing of spawning of Atlantic cod, Gadus morhua, has a major impact on occurrence, distribution, and development of eggs and larvae in a large embayment on the south coast of Newfoundland. Atlantic cod egg densities, measured with a series of ichthyoplankton surveys in Placentia Bay during the spawning and postspawning seasons of 1997 and 1998, were highest during the early spring of both years and decreased through the spring and summer. Egg development stages and larval size suggest that eggs and larvae were released from spawning locations within the bay and developed as they were transported in cyclonic flow from the southeast and around the bay towards the southwest, where late-stage eggs and larvae were found to be most abundant. Although egg densities were generally lower in 1998, late-season egg production during the summer of 1998 was elevated in relation to 1997, providing a possible explanation for the observation that larval total densities were more than an order of magnitude higher in 1998 than in 1997. In terms of larval production, late spawners may be particularly important to successful egg hatching in the coastal waters of Newfoundland.

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