Estimates of daily ration for the South African (Cape) fur seal

Balmelli, M.; Wickens, P. A.

doi:10.2989/025776194784287111

Cited by 28 publications

(18 citation statements)

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“…b Proxy was Sardinops sagax, from Prosch (1986), Jackson (1990, and Balmelli and Wickens (1994). c Proxy used was Engraulis capensis, from Batchelor and Ross (1984), Prosch (1986), Jackson (1990), and Balmelli and Wickens (1994). d Proxy was Sillago burrus and Sillago schomburgkii, this study.…”

Section: Distribution Of Predator and Preymentioning

confidence: 87%

“…Values for some species are those for closely related species in this or another system. a Proxy was Trachurus trachurus capensis, from Batchelor and Ross (1984), Prosch (1986), and Balmelli and Wickens (1994). b Proxy was Sardinops sagax, from Prosch (1986), Jackson (1990, and Balmelli and Wickens (1994).…”

Section: Distribution Of Predator and Preymentioning

confidence: 99%

“…a Proxy was Trachurus trachurus capensis, from Batchelor and Ross (1984), Prosch (1986), and Balmelli and Wickens (1994). b Proxy was Sardinops sagax, from Prosch (1986), Jackson (1990, and Balmelli and Wickens (1994). c Proxy used was Engraulis capensis, from Batchelor and Ross (1984), Prosch (1986), Jackson (1990), and Balmelli and Wickens (1994).…”

Section: Distribution Of Predator and Preymentioning

confidence: 99%

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Dolphin Prey Availability and Calorific Value in an Estuarine and Coastal Environment

2016

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Prey density has long been associated with prey profitability for a predator, but prey quality has seldom been quantified. We assessed the potential prey availability and calorific value for Indo-Pacific bottlenose dolphins (Tursiops aduncus) in an estuarine and coastal environment of temperate south-western Australia. Fish were sampled using three methods (21.5 m beach seine, multi-mesh gillnet, and fish traps), across three regions (Estuary, Bay, and Ocean) in the study area. The total biomass and numbers of all species and those of potential dolphin prey were determined in austral summers and winters between 2007 and 2010. The calorific value of 19 species was determined by bomb calorimetry. The aim of the research was to evaluate the significance of prey availability in explaining the higher abundance of dolphins in the region in summer vs. winter across years. A higher abundance of prey was captured in the summer (mean of two summer seasons 12,080 ± 160) than in the winter (mean of two winter seasons = 7358 ± 343) using the same number of gear sets in each season and year. In contrast, higher biomass and higher energy rich prey were captured during winters than during summers, when fewer dolphins are present in the area. Variability was significant between season and region for the gillnet (p < 0.01), and seine (p < 0.01). The interaction of season and region was also significant for the calorific content captured by the traps (p < 0.03), and between the seasons for biomass of the trap catch (p < 0.02). The dolphin mother and calf pairs that remain in the Estuary and Bay year round may be sustained by the higher quality, and generally larger, if lesser abundant, prey in the winter months. Furthermore, factors such as predator avoidance and mating opportunities are likely to influence patterns of local dolphin abundance. This study provides insights into the complex dynamics of predator-prey interactions, and highlights the importance for a better understanding of prey abundance, distribution and calorific content in explaining the spatial ecology of large apex predators.

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Section: Distribution Of Predator and Preymentioning

confidence: 87%

Section: Distribution Of Predator and Preymentioning

confidence: 99%

Section: Distribution Of Predator and Preymentioning

confidence: 99%

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Dolphin Prey Availability and Calorific Value in an Estuarine and Coastal Environment

2016

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“…calorific content (wet mass, kJ g À1 ), or energetic density (ED), of Cape fur seal prey items as presented by Balmelli and Wickens (1994) was used: Cape horse mackerel, 5.65 AE 0.80 kJ g À1 ; Cape hake, 4.47 AE 0.57 kJ g À1 ; lanternfish, 4.90 AE 0.80 kJ g À1 ; pelagic goby, 3.69 kJ g À1 (no s.d. ); pelagic fish, 6.18 AE 0.36 kJ g À1 (the average of sardine 6.59 kJ g À1 , anchovy 6.03 kJ g À1 , and round herring 5.91 kJ g À1 ); and others, 4.98 AE 0.60 kJ g À1 (average of the previous five prey groups).…”

Section: Energetic Density Of Preymentioning

confidence: 99%

“…Previous studies have estimated consumption of the Cape fur seal population as the product of population size and the daily prey requirement of an individual of average size, the latter assumed to be a set percentage of body weight (Shaughnessy, 1985;Butterworth et al, 1988;Wickens et al, 1992b), or from an allometric equation for growing marine mammals (Wickens et al, 1992b;Balmelli and Wickens, 1994;Smale et al, 1994;Butterworth et al, 1995). The more refined of these studies incorporated information on the population age structure (Butterworth et al, 1995), or apportioned the total consumption into prey groups using information on diet composition obtained from analyses of stomach contents (David, 1987).…”

Section: Introductionmentioning

confidence: 99%

A refined fish consumption model for lactating Cape fur seals (Arctocephalus pusillus pusillus), based on scat analyses

Mecenero

Kirkman

Roux³

2006

ICES Journal of Marine Science

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Mecenero, S., Kirkman, S. P., and Roux, J-P. 2006. A refined fish consumption model for lactating Cape fur seals (Arctocephalus pusillus pusillus), based on scat analyses. e ICES Journal of Marine Science, 63: 1551e1566.A refined fish consumption model for lactating Cape fur seals in Namibia during the eightmonth lactation period, which allows for spatio-temporal variation in the diet as determined by scat analyses, has been developed. Previous estimates of prey consumption by Cape fur seals have been based mostly on coarse diet composition models. Sensitivity analyses showed that the energetic requirement and mass of lactating females (bioenergetic variables), as well as the energetic density of prey (diet variable), contributed most to the uncertainty in consumption estimates. Uncertainty in the remaining input variables had minimal effects on the estimates of food consumption. The consumption of commercial prey (horse mackerel, hake and pelagic fish) was greatest by the colony at Cape Cross. The model estimated that a female of average mass 55 kg ingested, on average, 11% of her body mass per day. This model is easily applied to other age/sex classes of the seal population. It permits improvement of the estimates of prey consumption by seals, which are useful for assessing levels of competitive interactions between seals and fisheries or other predators, or the impacts of seals on prey species.

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Fatty acid composition of lipid-rich myctophids and mackerel icefish (Champsocephalus gunnari) – Southern Ocean food-web implications

2002

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The lipid content, fatty acid composition and calorific value of seven species of mesopelagic deep-sea fish of the family Myctophidae and the mackerel icefish, Champsocephalus gunnari, important in the diet of Southern Ocean marine predators, are presented. Fish were sampled at the Kerguelen Plateau (KP) and Macquarie Ridge (MR) in the Indian and Pacific sectors of the Southern Ocean respectively, to examine geographic variation in lipid compositon. All species of myctophid from KP and Electrona antarctica from MR were high in lipid content (6-18% wet mass), particularly Gymnoscopelus nicholsi (18%) and E. antarctica (15%). The mackerel icefish, and G. fraseri and Protomyctophum tenisoni from MR were generally lower in lipid content (3-5%) and varied significantly in fatty acid composition from KP species. KP myctophids were high in calorific content (9.3 kJ g-1 wet mass) when compared with icefish (5.4 kJ g-1 wet mass) and other published values for prey items of marine predators such as squid (1.7-4.5 kJ g-1). KP myctophids were distinguished from each other and from C. gunnari and MR specimens by cluster and discriminant function analysis using six fatty

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Estimates of daily ration for the South African (Cape) fur seal

Cited by 28 publications

References 0 publications

Dolphin Prey Availability and Calorific Value in an Estuarine and Coastal Environment

Dolphin Prey Availability and Calorific Value in an Estuarine and Coastal Environment

A refined fish consumption model for lactating Cape fur seals (Arctocephalus pusillus pusillus), based on scat analyses

Fatty acid composition of lipid-rich myctophids and mackerel icefish (Champsocephalus gunnari) – Southern Ocean food-web implications

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