Seasonal variation in the habitat associations of Atlantic cod (<i>Gadus morhua</i>) and American plaice (<i>Hippoglossoides platessoides</i>) from the southern Gulf of St. Lawrence

Swain, Douglas P.; Chouinard, Ghislain A.; Morin, Roderick; Drinkwater, Ken

doi:10.1139/f98-122

Cited by 61 publications

(55 citation statements)

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“…They forage primarily on the Scotian Shelf, a broad, shallow ocean margin off Canada's east coast characterised by complex glacially altered bathymetry and an ecosystem that has been highly disturbed by overfishing (Frank et al 2005). This region is temperate at 44°N and, typical of temperate oceans, has strong annual cycles of ocean productivity and temperature, major annual fish migrations (which affects prey availability) and strong seasonal changes in fish condition (which affects prey quality) (Perry & Smith 1994, Swain et al 1998, Comeau et al 2002. Seasonality in foraging behaviour has been detected in adults from this population (Beck et al 2003a, Austin et al 2006, Breed et al 2006.…”

Section: Introductionmentioning

confidence: 94%

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Development of foraging strategies with age in a long-lived marine predator

Breed¹,

Bowen²,

Leonard³

2011

Mar. Ecol. Prog. Ser.

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The development of foraging strategies as animals mature depends upon experience, stage-specific physiology, the onset of reproductive maturity and the reproductive costs incurred by each sex. To understand the ontogeny of foraging behaviour, we compared movement behaviour of 24 young-of-year (YOY) juveniles (12 male, 12 female) with 6 subadult (4 male, 2 female) and 81 adult (43 male, 38 female) grey seals Halichoerus grypus. We used a behaviour discriminating state-space model followed by a series of mixed-effects models to examine trip structure and habitat use in these age classes. In foraging trips, tortuosity and speed of outbound travel were not different in YOY, subadults and adults, suggesting that YOY navigate as well as older animals. On average, however, YOY trips lasted 1.2 to 3.5 d longer and required up to twice as much transit time to reach foraging areas that were 1.5 to 3 times farther from haul-out sites than those of subadults and adults. This suggests an overall apparent higher foraging effort for YOY. Differences, however, were highly seasonally dependent. In all groups, apparent foraging effort decreased in the summer and increased in the winter, which is consistent with seasonal changes in prey distribution and energy content. Adult foraging patterns showed complex seasonal patterns influenced by both reproductive cycles and seasonal environmental variation, whereas annual foraging patterns of YOY and subadults, neither of which invest in reproduction, were simpler and appeared more closely tied to seasonal changes in prey availability and condition. Although foraging in the same habitats, male and female YOY showed small but significant differences in movement behaviour and trip structure. These differences are unlikely to be due to size difference, which is minimal at this age, and suggest that sex-related differences in foraging develop early before sexual size dimorphism is significantly expressed.

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Section: Introductionmentioning

confidence: 94%

“…Conversely, decreased summer effort occurs when many prey move into shallower nearshore waters and the tops of banks (Perry & Smith 1994, Swain et al 1998. Prey species also show pronounced annual cycles in energy density, becoming lipid rich in the summer prior to spawning and losing condition through the winter.…”

Section: Annual Foraging Routinesmentioning

confidence: 99%

Development of foraging strategies with age in a long-lived marine predator

Breed¹,

Bowen²,

Leonard³

2011

Mar. Ecol. Prog. Ser.

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“…The summer depth distributions of cod populations located within the general latitudinal range of the Flemish Cap tend to be shallow. During summer, cod are distributed at median depths of 144 to 181 m in the northern Gulf of St. Lawrence (Castonguay et al, 1999) and 46 to 51 m in the southern Gulf of St. Lawrence (Swain et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Density-dependent changes in the spatial distributions of Atlantic Cod (Gadus morhua), American Plaice (Hippoglossoides platessoides), and Greenland Halibut (Reinhardtius hippoglossoides) on the Flemish Cap during 1988-2002

Hendrickson¹,

Vázquez²

2005

J. Northw. Atl. Fish. Sci.

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The Flemish Cap is an isolated bank located east of the Grand Banks in the Northwest Atlantic Ocean. Research bottom trawl surveys of the Flemish Cap have been conducted in July by the European Union since 1988. Data from these surveys were used to assess changes in the spatial distributions of Atlantic cod (Gadus morhua), American plaice (Hippoglossoides platessoides), and Greenland halibut (Reinhardtius hippoglossoides) during 1988-2002. Kriging and indices of collocation and co-occurrence indicated that cod and plaice distributions have a high degree of overlap and that density-dependent range contraction of both stocks occurred during a time when Greenland halibut, a more common inhabitant of deep water, exhibited range expansion into shallow water on the Cap. However, the timing and locations of these distributional changes were such that little overlap occurred between the distributions of Greenland halibut and either cod or plaice. The range expansion of Greenland halibut was also density-dependent and primarily attributable to young fish (ages 1 and 2 from the 1994 and 1995 year-classes) which prefer shallow water. The range contractions of cod and plaice have persisted since the mid-1990s, and despite fishing moratoria implemented for plaice in 1994 and for cod in 1999, neither stock has shown signs of recovery. Biological and stock assessment implications of these distribution changes are discussed in relation to the lack of recovery.

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“…Many of these fishes, particularly cod, are highly aggregated in winter. Larger fish tend to be associated with deeper water further down the slope of the channel (Swain et al 1998). This seasonal shift in the Gulf fish community coincides with a shift in distribution of grey seals as animals leave the estuary and northern Gulf and move into the southern Gulf or Table 2.…”

Section: Discussionmentioning

confidence: 99%

“…Most commercial fish species leave the southern Gulf in late fall, overwintering in the deep waters of the Laurentian Channel or along its southern slope (e.g. Swain et al 1998). Northwest Atlantic grey seals are widely distributed throughout this area and over the Scotian shelf in summer.…”

Section: Study Areamentioning

confidence: 99%

Winter foraging by a top predator, the grey seal Halichoerus grypus, in relation to the distribution of prey

Harvey¹,

Hammill²,

Swain³

et al. 2012

Mar. Ecol. Prog. Ser.

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Identifying foraging areas of individuals and correlating them with potential food resources allows for a better understanding of predator-prey relationships. Herein, we examine whether grey seal movements were associated with overwintering concentrations of several commercial fish species in the Cabot Strait, Atlantic Canada, using data from satellite transmitters deployed on grey seals (between 1993 and 2005) and winter bottom-trawl survey data (1994 to 1997). The distribution of searching effort by male grey seals varied throughout the winter. In early winter, males concentrated their movements around St. Paul's Island. In late winter, they were found to the southeast of this area, where females also occurred. The fish community differed between apparent foraging and non-foraging areas. Densities of small plaice, hake and redfish, large herring and cod of all sizes were relatively high in the male grey seal foraging zones; female foraging zones were characterized by higher densities of small plaice and redfish and large cod. Areas where grey seal foraging was not concentrated were characterized by high densities of medium and large redfish as well as large turbot and witch flounder. Diet samples are needed to determine whether grey seals are feeding on the fish groups that distinguish foraging from nonforaging areas or alternatively on other prey that occur in the same areas.KEY WORDS: Marine predator · Foraging areas · Cod · Spatial overlap · First-passage time · Groundfish · Gulf of St. Lawrence Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 462: [273][274][275][276][277][278][279][280][281][282][283][284][285][286] 2012 spond to annual losses of < 5% of adult cod to fishing and ~45% to natural mortality. It has been suggested that predation by an increasing grey seal population (Thomas et al. 2008) may be an important factor in the elevated natural mortality of adult cod (Chouinard et al. 2005, Benoît & Swain 2008, Swain et al. 2009). However, diet studies from the southern Gulf have not supported the hypothesis that seals are consuming large numbers of large cod (e.g. Hammill et al. 2007). But these studies, which are based on prey hard parts (in particular otoliths or ear bones) found in the digestive tracts of seals, may underestimate the consumption of large fish if their heads are not consumed (Hauser et al. 2008, Phillips & Harvey 2009 or if sampling has not occurred where grey seals and large fish overlap (Benoît et al. 2011).The overwintering period, when southern Gulf cod occur in dense aggregations at consistent locations (see 'Results'), is a period when cod may be an attractive prey resource to grey seals. However, sampling of seals for diet studies at this time of year is logistically challenging. In theory, the availability and distribution of resources is expected to affect the distribution of animals as well as their space-use strategy (Johnson 1980, Manly et al. 2002, and effective predators should concentrate effort in areas ...

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Seasonal variation in the habitat associations of Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) from the southern Gulf of St. Lawrence

Cited by 61 publications

References 0 publications

Development of foraging strategies with age in a long-lived marine predator

Development of foraging strategies with age in a long-lived marine predator

Density-dependent changes in the spatial distributions of Atlantic Cod (Gadus morhua), American Plaice (Hippoglossoides platessoides), and Greenland Halibut (Reinhardtius hippoglossoides) on the Flemish Cap during 1988-2002

Winter foraging by a top predator, the grey seal Halichoerus grypus, in relation to the distribution of prey

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