Spatial Comparison of Recent Growth in Postlarval Atlantic Cod (Gadus morhua) off Southwestern Nova Scotia: Inferior Growth in a Presumed Nursery Area

1989 ◽  
Vol 46 (S1) ◽  
pp. s113-s124 ◽  
Author(s):  
Iain M. Suthers ◽  
Kenneth T. Frank ◽  
Steven E. Campana
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Zooplankton Biomass ◽  
Early Summer ◽  
Sampling Area ◽  
Common Environment ◽  
Sea Temperature ◽  
Recent Growth ◽  
Otolith Increment

Spatial variation in distribution, age, and recent growth of postlarval cod (Gadus morhua) were examined off southwestern Nova Scotia during the early summer of 1985 and 1986. Ages ranged between 40–120 d posthatch throughout the sampling area, from the spawning grounds on Browns Bank, to nearshore (<55 m depth) and offshore regions 150 km north. The hatch-date distributions during 1986 between cruises 3 wk apart were significantly different in the nearshore, contrary to the age structure on the Bank which appeared more stable. These observations are consistent with retention of cod in the Browns Bank gyre, coupled with episodic leakage and northerly advection in the residual current. Recent growth determined from otolith increment widths was significantly less for those cod sampled at nearshore stations than for cod offshore and on the Bank. Recent growth was significantly correlated with Zooplankton biomass in a size range suitable for postlarval cod, while sea temperature was correlated in only one cruise. Nearshore areas had on average 25% of the Zooplankton biomass found on the Bank. Recent growth indices of the third and fourth week precapture were not significantly different between the nearshore and offshore, implying that the cod had shared a common environment, and common origin such as Browns Bank.

Structure and Interannual Variability of the Plankton and its Environment off Southwest Nova Scotia in Late Spring and Early Summer

1989 ◽  
Vol 46 (S1) ◽  
pp. s44-s54 ◽  
Author(s):  
J. Anthony Koslow ◽  
R. Ian Perry ◽  
Peter C. F. Hurley ◽  
Robert O. Fournier
Keyword(s):  
Nova Scotia ◽  
Chlorophyll A ◽  
North Atlantic ◽  
Atmospheric Pressure ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Early Summer ◽  
Tidal Mixing ◽  
Secondary Importance ◽  
The North

Consistent alongshore and/or onshore–offshore gradients in temperature, salinity, and inorganic nutrient were observed off southwest Nova Scotia in June/July, 1981–85. The distributions were established primarily by mixing of relatively warm, high-salinity, nutrient-rich Slope Water with the cold, low-salinity, nutrient-poor water of the Nova Scotia Current. Tidal mixing and frontal dynamics were of secondary importance. Consistent with the distribution of nutrient and the earlier onset of stratification offshore, chlorophyll a concentrations were generally highest offshore and lowest inshore, and the distributions of Zooplankton displacement volume and of dominant copepod species were similar. Salinity, nutrient, and chlorophyll a concentrations and the abundance of zoo-plankton were all generally higher throughout the spring of 1985 than in 1983–84. In 1985, there was greater upwelling and Slope Water influence and decreased flow of the shelf current. This was associated with a reversal of the North Atlantic atmospheric pressure anomaly field, which led to predominantly offshore and southwest alongshore winds in winter and spring, 1985. Correlations of recruitment to northwest Atlantic cod (Gadus morhua) stocks with wind and North Atlantic atmospheric pressure anomalies (Koslow et al. 1987) may be based upon the wind's influence on nutrient availability and plankton abundance.

Natural mortality from poor condition in Atlantic cod (Gadus morhua)

2000 ◽  
Vol 57 (4) ◽  
pp. 826-836 ◽  
Author(s):  
Jean-Denis Dutil ◽  
Yvan Lambert
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Negative Impact ◽  
Fish Muscle ◽  
Early Summer ◽  
Wild Fish ◽  
Natural Mortality ◽  
Muscle Lactate ◽  
Lactate Dehydrogenase Activity ◽  
Poor Condition

The extent of energy depletion was assessed in Atlantic cod (Gadus morhua) in spring and early summer (1993-1995) to assess relationships between poor condition and natural mortality. Several indices of condition were compared in wild fish in the northern Gulf of St. Lawrence and in fish exposed to a prolonged period of starvation in laboratory experiments. Discriminant analyses classified only a small fraction of the wild fish as similar to cod that did not survive and a much larger fraction as similar to cod that survived starvation. This percentage increased from April to May and peaked in June 1993 and 1994. Condition factor and muscle somatic index allowed a clear distinction between live and dead fish. Muscle lactate dehydrogenase activity suggested that cod had experienced a period of negative growth early in 1993, 1994, and 1995. Fish classified as similar to starved individuals were characterized by a higher gonad to liver mass ratio than others. Reproduction may have a negative impact on survival not only in spring but also later into summer, as some individuals were found not to have recovered by late summer. This study shows that natural mortality from poor condition contributed to lower production in the early 1990s.

Recent Growth, Biochemical Composition and Prey Field of Larval Haddock (Melanogrammus aeglefinus) and Atlantic Cod (Gadus morhua) on Georges Bank

1987 ◽  
Vol 44 (1) ◽  
pp. 14-25 ◽  
Author(s):  
L. J. Buckley ◽  
R. G. Lough
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Dry Weight ◽  
Melanogrammus Aeglefinus ◽  
Good Growth ◽  
Georges Bank ◽  
Larval Population ◽  
Prey Biomass ◽  
Recent Growth ◽  
Haddock Melanogrammus Aeglefinus

A transect across southern Georges Bank in May 1983 showed higher levels of available prey for haddock (Melanogrammus aeglefinus) and cod (Gadus morhua) larvae at two stratified sites than at a well-mixed site. At the stratified sites, prey biomass was high (30–300 μg dry wt∙L−1) near the surface above the thermocline; values were lower and more uniform with depth (10–30 μg dry wt∙L−1) at the well-mixed site. Larval population centers generally coincided with prey biomass vertically. Recent growth in dry weight of haddock larvae as estimated by RNA–DNA ratio analysis was higher at the stratified sites (8–13%∙d−1) than at the well-mixed site (7%∙d−1). Larvae appeared to be in excellent condition at the stratified sites, but up to 50% of haddock larvae from the well-mixed site had RNA–DNA ratios in the range observed for starved larvae in the laboratory. Cod collected at the same site were in better condition and growing faster than haddock. The data support the hypotheses that (1) stratified conditions in the spring favor good growth and survival of haddock larvae and (2) cod larvae are better adapted to grow and survive in well-mixed waters at lower levels of available food than haddock larvae.

Some ectoparasitic trichodinids from Atlantic cod, Gadus morhua L., with a description of Trichodina cooperi n.sp.

1989 ◽  
Vol 67 (7) ◽  
pp. 1793-1800 ◽  
Author(s):  
S. L. Poynton ◽  
J. Lom
Keyword(s):  
Nova Scotia ◽  
Body Surface ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Geographic Range ◽  
The Body ◽  
Wild Fish ◽  
Eastern Canada ◽  
Mean Diameter ◽  
The Mean

Trichodina murmanica Polyanskiy, 1955 (= Trichodina domerguei subsp. saintjohnsi Lom and Laird, 1969) and Trichodina cooperi n.sp. were commonly encountered on skin and fins of Atlantic cod, Gadus morhua L., near Halifax, Nova Scotia, Canada. A third species of Trichodina, probably new, was recorded from the skin of one fish. This is believed to be the first report of the genus Trichodina from the body surface of gadoid fish from eastern Canada, and the known geographic range of T. murmanica is extended. Trichodina cooperi n.sp. has an adoral ciliary spiral of 370–380° and is relatively large, the mean diameter of the body is 110 μm, of the adhesive disc (with dark center), 95 μm, and of the denticulate ring, 59 μm. The denticulate ring consists of 24–29 denticles (usually 27), with 7–9 radial pins per denticle. Each denticle has a broad blade, a large central part, and a slightly curved thorn of moderate to broad width, with a central rib when mature. The thorn is approximately twice the length of the blade. The horseshoe-shaped macronucleus has a diameter of 80.0 μm and the micronucleus is in the +y position. Trichodina spp. infected 26% of 39 wild fish 20 to < 60 cm long. Most wild fish yielded less than five ciliates per 24 × 50 mm smear.

Substock variation in reproductive traits in North Sea cod (Gadus morhua)

2010 ◽  
Vol 67 (5) ◽  
pp. 866-876 ◽  
Author(s):  
Marion Harrald ◽  
Peter J. Wright ◽  
Francis C. Neat
Keyword(s):  
Spatial Variation ◽  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Liver Weight ◽  
Adaptive Divergence ◽  
Female Size ◽  
Common Environment ◽  
Relative Liver Weight ◽  
Trade Offs

The North Sea stock of Atlantic cod ( Gadus morhua ) is comprised of a number of subcomponents that differ both genetically and phenotypically. A potential cause for such spatial variability is adaptive divergence, which may be linked to differences in thermal environment and (or) historical fishing pressure. Here we present evidence that spatial variation in maturity–size relationships in the wild has a significant intrinsic component. Using a common-environment experiment on wild-caught juveniles raised through to maturity, we demonstrate that cod from the southern North Sea (SNS) mature at larger sizes than those from the northwestern North Sea (NWNS) despite broadly similar growth rates. Consistent with these experimental results, year-class-specific maturity ogives for recent maturing year classes (1999–2001) suggested that the length at which 50% of females reached maturity was 11 cm greater for SNS than for NWNS cod. Under a common environment, smaller female size at maturity partly reflected higher relative liver weight, with NWNS females having a higher relative liver weight than SNS females. By investigating maturation under controlled conditions, our study provides evidence for life history trade-offs in energy allocation between growth, energy storage, and reproduction that may underlie the spatial variation observed in the field.

Studies on the Life-History of the Ascarid Porrocaecum decipiens in the Bras d'Or Lakes, Nova Scotia, Canada

1960 ◽  
Vol 17 (6) ◽  
pp. 763-774 ◽  
Author(s):  
D. M. Scott ◽  
W. F. Black
Keyword(s):  
Life History ◽  
Nova Scotia ◽  
Intermediate Host ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Phoca Vitulina ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Important Food ◽  
History Of

Larvae of the parasitic ascarid (Porrocaecum decipiens) occurred commonly in the musculature and viscera of Atlantic cod (Gadus morhua) in the Bras d'Or Lakes. They were also present in the musculature of nine other species of teleosts and probably also in the viscera of skates (Raja sp.). Most larvae were longer than 20 mm. None was shorter than 10 mm, a fact which suggested the existence of some earlier intermediate host, probably an invertebrate. More than 8,000 mysids, an important food of fishes when they first become infected, were examined for nematodes. Although 110 nematodes were found, only one certainly and four dubiously appeared to be Porrocaecum. The definitive hosts were the harbour seal (Phoca vitulina) and the grey seal (Halichoerus grypus). The distribution of seals coincided with local variations in the incidence of the parasite in cod.

Survival and Abundance of Young Atlantic Cod (Gadus morhua) and Haddock (Melanogrammus aeglefinus) as Indicators of Year-class Strength

1989 ◽  
Vol 46 (S1) ◽  
pp. s171-s182 ◽  
Author(s):  
Steven E. Campana ◽  
Kenneth T. Frank ◽  
Peter C. F. Hurley ◽  
Peter A. Koeller ◽  
Fred H. Page ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Larval Mortality ◽  
Larval Growth ◽  
Melanogrammus Aeglefinus ◽  
Larval Abundance ◽  
Life History Stage ◽  
Spawning Site ◽  
Haddock Melanogrammus Aeglefinus

To identify the life history stage(s) most influential in determining yearclass strength, we constructed and analyzed survival curves of the 1983, 1984, and 1985 cohorts of cod and haddock off Southwest Nova Scotia relative to their physical and biological environment. Relative abundance of each Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) yearclass was not reflected by egg or larval abundance in any year examined. However, abundance of both pelagic and settled juveniles did appear to reflect yearclass strength. Egg and larval mortality could not be consistently linked with advection from the spawning site, and did not covary with subsequent recruitment. In both species, mortality between the larval and juvenile stage was inversely correlated with yearclass strength, but sources of the mortality could not be identified. Larval growth was inversely related to mortality of the early larval stage and independent of larval abundance. However, juvenile growth was proportional to mortality and inversely related to abundance. Despite early life coexistence and similarities in spawning time and location, the relative yearclass strengths of cod and haddock in Southwest Nova Scotia were different, suggesting that the timing of local physical and biological events may play an important role in the recruitment success of these stocks.

Why the Atlantic cod (Gadus morhua) stock off eastern Nova Scotia has not recovered

2001 ◽  
Vol 58 (8) ◽  
pp. 1613-1623 ◽  
Author(s):  
Caihong Fu ◽  
Robert Mohn ◽  
L Paul Fanning
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Commercial Fishing ◽  
Sudden Increase ◽  
Annual Variations ◽  
Structured Population ◽  
Population Dynamics Model ◽  
Structured Population Dynamics ◽  
Age Structured

An age-structured population dynamics model, incorporating interactions between Atlantic cod (Gadus morhua), the fishery, and the grey seal (Halichoerus grypus) population, was applied to the cod stock off eastern Nova Scotia (Northwest Atlantic Fisheries Organization Divisions 4Vs and 4W, commonly abbreviated to 4VsW), a stock that has dramatically declined since the late 1980s. Mortality was modeled as having three components: fishing mortality (F), seal predation (Mp), and all other sources of natural mortality (M). Specifically, M was assumed to be distinct for immature cod (ages 1–4; Mi) and mature cod (age 5 and older; Mm), and respective annual variations were estimated. Parameters estimated also included recruitment (cod abundance at age 1; R), F, and Mp. Based on our estimates of F, Mp, and M, it is unlikely that the collapse of the 4VsW cod stock can be attributed to a sudden increase in M; fishing appears to have been the primary cause for the stock's decline. However, after the moratorium on commercial fishing in 1993, increasing Mp and Mm and low R may have contributed to the failure of the 4VsW cod stock to recover.

Distribution and Abundance of Haddock (Melanogrammus aeglefinus) and Atlantic Cod (Gadus morhua) Eggs and Larvae in the Waters off Southwest Nova Scotia

1989 ◽  
Vol 46 (S1) ◽  
pp. s103-s112 ◽  
Author(s):  
Peter C. F. Hurley ◽  
Steven E. Campana
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Melanogrammus Aeglefinus ◽  
Eggs And Larvae ◽  
Haddock Melanogrammus Aeglefinus ◽  
Egg Abundance

Synoptic ichthyoplankton surveys conducted at monthly intervals during the winter–spring of 1983–85 were used to determine the location, timing, and magnitude of spawning by haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua) off southwest Nova Scotia. There was a marked similarity in the spawning locations of the two species: primary spawning occurred on Browns Bank, although lower levels of spawning were observed on adjacent banks and in the inshore region. Cod egg abundance peaked in April in all years, while that of haddock varied between April–June.

Interactive Effects of Geophysically-Forced Sea Temperatures and Prey Abundance on Mesoscale Coastal Distributions of a Marine Predator, Atlantic Cod (Gadus morhua)

1989 ◽  
Vol 46 (11) ◽  
pp. 1904-1913 ◽  
Author(s):  
G. A. Rose ◽  
W. C. Leggett
Keyword(s):  
Coastal Zone ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Distribution Patterns ◽  
Prey Abundance ◽  
Interactive Effects ◽  
Mallotus Villosus ◽  
Sea Temperature ◽  
Marine Predator ◽  
Capelin Mallotus Villosus

Geophysically-forced sea temperatures and prey abundance interactively regulated mesoscale (10's to 100's of km) inshore Atlantic Cod (Gadus morhua) distribution patterns in the northeastern Gulf of St. Lawrence, in both 1985 and 1986. Cod were located most often at temperatures within the range 0–5 °C. However, when mean densities of their chief prey (capelin, Mallotus villosus) were high (> 100/105m3) within the coastal zone, cod frequented waters having temperatures similar to those at which this prey were aggregated, within the broader range of temperatures −0.5 to 8.5 °C. The proportions of cod occupying sea temperature strata were significantly and positively correlated with those of capelin (r = 0.64, slope = 0.6, df = 86), in both 1985 and 1986, under two conditions: (1) sea temperatures within the range 1–9 °C; and (2) mean capelin densities > 100/105m3. Under conditions of lower mean capelin densities, cod distributions were independent of those of capelin. At temperatures outside the range 1–9 °C, cod and capelin densities were not correlated, regardless of capelin densities.

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