scholarly journals Diet and prey preferences of larval and pelagic juvenile Faroe Plateau cod (Gadus morhua)

2020 ◽  
Vol 167 (8) ◽  
Author(s):  
Sólvá Jacobsen ◽  
Kristoffer Klitgaard Nielsen ◽  
Rune Kristiansen ◽  
Peter Grønkjær ◽  
Eilif Gaard ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Prey Preferences ◽  
Pelagic Juvenile

Diet overlap and prey selection through metamorphosis in Irish Sea cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and whiting (Merlangius merlangus)

2008 ◽  
Vol 65 (7) ◽  
pp. 1297-1306 ◽  
Author(s):  
William Ll. Rowlands ◽  
Mark Dickey-Collas ◽  
Audrey J. Geffen ◽  
Richard D.M. Nash
Keyword(s):  
Gadus Morhua ◽  
Prey Selection ◽  
Stomach Contents ◽  
Irish Sea ◽  
Melanogrammus Aeglefinus ◽  
Prey Preferences ◽  
Merlangius Merlangus ◽  
The Irish Sea ◽  
Haddock Melanogrammus Aeglefinus ◽  
Calanus Species

Copepods in the genus Calanus are usually considered to be the preferred prey of gadoid larvae in many areas; however, in the Irish Sea, the abundances of these Calanus species are low and highly variable. We use this situation to test whether Calanus species are still actively selected by gadoid larvae in Calanus -poor environments. Diets of Irish Sea cod ( Gadus morhua ), haddock ( Melanogrammus aeglefinus ), and whiting ( Merlangius merlangus ) were studied from the yolk-sac stage to the juvenile stage. Prey from stomach contents were compared with in situ abundance via an index of prey preference. As expected, all larvae selected copepod nauplii at the onset of feeding. As the larvae developed, their prey preferences changed and varied with species. Cod and whiting showed a similar transition of prey species preference, with a clear preference for Calanus species after metamorphosis, even in this area of low abundance of these Calanus species. The diet composition of haddock differed from that of cod and whiting, as nauplii remained in their diet later into development and there was little preference for individual copepod species detected. The differences in prey selectivity suggested between these gadoids may be attributed to their population variability through the known variability of their preferred prey items.

Inter-Annual Distributions of Larval and Pelagic Juvenile Cod (Gadus morhua) in Southwestern Nova Scotia determined with two Different Gear Types

1989 ◽  
Vol 46 (4) ◽  
pp. 591-602 ◽  
Author(s):  
Iain M. Suthers ◽  
Kenneth T. Frank
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Empirical Support ◽  
Single Type ◽  
Sampling Effort ◽  
Limited Sampling ◽  
Inshore Waters ◽  
Made In ◽  
Spawning Sites ◽  
Pelagic Juvenile

Ichthyoplankton surveys conducted during 1979 on the Scotian Shelf have shown coincident egg and larval distributions for cod (Gadus morhua) and other related groundfish species. These data have been used by other investigators to support the larval retention hypothesis, in spite of three limitations: the exclusive use of a single type of small sampling gear, limited sampling landward of the 50-m isobath, and analysis of data collected in a single year. During May of 1985, 1986, and 1987 two gear types were used, from the shelf to coastal waters in southwestern Nova Scotia to assess the horizontal distributions of larval and pelagic juvenile cod. Tucker trawl collections made in each year revealed a cohort of cod [Formula: see text] that was not evident in the smaller gear, which effectively sampled cod larvae < 10 mm. During 1985 and 1986, when both larvae and juveniles were abundant, their distributions coincided. The mixture of sizes of cod from 3–45 mm reduced the importance of using multiple gear types. The interannual location of young cod shifted markedly between the nearshore and offshore demonstrating that a single year of sampling effort is inadequate to assess their distribution. Nearshore sampling revealed high densities of young cod as much as three-fold greater than offshore. The inshore waters may serve as a nursery area for young cod originating from offshore spawning sites. Our results confirm the existence of two important sampling limitations of previous cod ichthyoplankton surveys that reduce their utility as empirical support for the retention hypothesis.

Offshore spawning and year-class strength of northern cod (2J3KL) during the fishing moratorium, 1994-1996

2001 ◽  
Vol 58 (7) ◽  
pp. 1386-1394 ◽  
Author(s):  
John T Anderson ◽  
George A Rose
Keyword(s):  
Gadus Morhua ◽  
Juvenile Fish ◽  
Late Summer ◽  
Rapid Decline ◽  
Natural Mortality ◽  
Potential Fecundity ◽  
Larval Stages ◽  
Northern Cod ◽  
Class Strength ◽  
Pelagic Juvenile

Two new surveys have been conducted in recent years to assess the status of the northern cod (Gadus morhua) stock (2J3KL). An offshore acoustic survey in spring sampled concentrations of spawning adults and estimated potential fecundity. A pelagic juvenile fish survey carried out in late summer measured cod year-class strength prior to settlement. Spawning biomass of offshore cod decreased from 11 700 t in 1994 to 2000 t in 1995 to 900 t in 1996 with a corresponding decrease in eggs spawned. This decline was mirrored in the distribution and abundance of pelagic juvenile cod. Natural mortality estimated between the egg and pelagic juvenile stages increased from –0.068·day–1 in 1994 to –0.084·day–1 in 1995 to –0.112·day–1 in 1996. The decline in year-class strength of cod appeared to result primarily from a reduction in the number of offshore spawners compounded by an increase in natural mortality during the egg and larval stages. The decline in spawners occurred 2 years after the implementation of a fishing moratorium and cannot be linked to fishing. The rapid decline in abundance of adult fish combined with increased natural mortality during the egg and larval drift is consistent with depensation.

Abundance and distribution of pelagic 0-group cod (Gadus morhua) in Newfoundland waters: inshore versus offshore

1995 ◽  
Vol 52 (1) ◽  
pp. 115-125 ◽  
Author(s):  
J. T. Anderson ◽  
E. L. Dalley ◽  
J. E. Carscadden
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Offshore Area ◽  
The North ◽  
Spawning Areas ◽  
Northern Cod ◽  
Primary Habitat ◽  
Abundance And Distribution ◽  
Eggs And Larvae ◽  
Pelagic Juvenile

The Northern cod stock has previously been described as undergoing a large-scale denatant–contranatant migration during which spawning occurs primarily in the north off Labrador. Eggs and larvae are advected southward to the inshore areas along the NE coast of Newfoundland where they settle as juveniles, then there is a gradual return migration to the northern spawning areas. We examined abundance distributions of pelagic juvenile (0-group) cod in the fall between inshore and offshore areas to determine if these fish occurred predominantly inshore following pelagic drift. Comparison between areas demonstrated no differences in abundances and mean sizes. Our results do not support the concept of large-scale advection of eggs and larvae spawned offshore to inshore areas, but indicate that cod eggs spawned offshore remain offshore. Back calculations of spawning times indicate the pelagic juvenile cod sampled offshore were spawned predominantly in April, whereas fish caught inshore were spawned predominantly in May-June, as well as April. Estimates of spawning abundance indicate that the inshore areas along the NE coast of Newfoundland may represent <10% of eggs spawned annually. Historically, the offshore area appears to have been the primary habitat for pelagic juvenile cod.

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