Otolith chemistry is more accurate than otolith shape in identifying cod species (genus Pseudophycis) in the diet of Australian fur seals (Arctocephalus pusillus doriferus)

2011 ◽  
Vol 68 (10) ◽  
pp. 1732-1743 ◽  
Author(s):  
Jodie Kemp ◽  
Stephen E. Swearer ◽  
Gregory P. Jenkins ◽  
Simon Robertson
Keyword(s):  
Fourier Analysis ◽  
Significant Variation ◽  
Prey Species ◽  
Fine Scale ◽  
Accurate Identification ◽  
Fish Prey ◽  
Otolith Shape ◽  
Discriminant Model ◽  
Fur Seals ◽  
Otolith Core

Fine-scale shape variation and the added effect of partial digestion often limits accurate identification of different teleost prey species in marine diet studies using otoliths. We evaluated the use of fine-scale shape and trace element variation in digested otoliths to identify fish prey species from the diet of predators. Fourier analysis of otolith shape revealed significant variation between red cod ( Pseudophycis bachus ) and bearded rock cod ( Pseudophycis barbata ) otoliths. Incorporating otoliths that had been consumed by Australian fur seals ( Arctocephalus pusillus doriferus ) into a Fourier analysis discriminant model identified 73% of otoliths as those of red cod and 27% as those of bearded rock cod. However, in vitro digestion of red cod and bearded rock cod otoliths resulted in incorrect classification of both cod species otoliths to varying degrees when using Fourier analysis shape descriptors. There was significant variation between red cod and bearded rock cod otolith core chemistry. Incorporating otoliths consumed by the seals into an otolith core chemistry discriminant model identified all otoliths as those of red cod. Using otolith core chemistry to identify prey species was found to be successful, and there is great potential for this technique to have wider applications in investigating ecosystem trophic interactions.

Oceanographic factors influencing the distribution of South American fur seal, Arctocephalus australis around the Falkland Islands before the breeding season

2009 ◽  
Vol 89 (8) ◽  
pp. 1597-1600 ◽  
Author(s):  
Vladimir Laptikhovsky
Keyword(s):  
Prey Species ◽  
Falkland Islands ◽  
South American ◽  
Important Food ◽  
Factors Influencing ◽  
South West ◽  
Fur Seals ◽  
Fur Seal ◽  
Important Food Source ◽  
Productive Zone

Distribution of fur seals Arctocephalus australis has been studied in October 2007 on the western, southern and eastern Falkland shelves during the survey of spawning grounds of the red cod, Salilota australis. Fur seals presence/absence, numbers and sex were recorded at every oceanographic station. Animals were found foraging on the shelf edge south-west of the islands, in a productive zone with quasi-stationary eddies at a periphery of upwelling. It was also the zone of maximum abundance of lobster-krill, Munida spp.—an important food source of fur seals and aggregations of both red cod and blue whiting, Micromesistius australis. No fur seals were found in waters of the relative cold and saline Falkland Current as well as in the relatively warm, fresh and oxygen-rich waters of Argentine Drift. It allows supposing that position and extension of the foraging grounds are caused by oceanographic features determining distribution of prey species.

scholarly journals Trends in numbers of Cape gannets (Morus capensis), 1956/1957–2005/2006, with a consideration of the influence of food and other factors

2006 ◽  
Vol 64 (1) ◽  
pp. 169-177 ◽  
Author(s):  
Robert J. M. Crawford ◽  
Benedict L. Dundee ◽  
Bruce M. Dyer ◽  
Norbert T. W. Klages ◽  
Michael A. Meÿer ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
Conservation Status ◽  
Fish Prey ◽  
Management Measures ◽  
Fur Seals ◽  
Long Term Changes ◽  
Influence Of Food ◽  
Abundance And Distribution

Abstract Crawford, R. J. M., Dundee, B. L., Dyer, B. M., Klages, N. T., Meÿer, M. A., and Upfold, L. 2007. Trends in numbers of Cape gannets (Morus capensis), 1956/57–2005/06, with a consideration of the influence of food and other factors – ICES Journal of Marine Science, 64, 169–177. Cape gannets (Morus capensis) breed at six colonies in Namibia and South Africa. Population size averaged about 250 000 pairs over the period 1956/1957–1968/1969 and about 150 000 pairs from 1978/1979 to 2005/2006. Over the whole 50-y period, numbers at the three Namibian colonies fell by 85–98%, with greater proportional decreases in the south. There were increases at two South African colonies between 1956/1957 and 2005/2006. The colony at Lambert's Bay increased between 1956/1957 and 2003/2004, but attacks by Cape fur seals (Arctocephalus pusillus) on birds at nests caused abandonment of the entire colony in 2005/2006. Long-term changes at colonies are thought to be largely attributable to an altered abundance and distribution of prey, especially sardine (Sardinops sagax) and anchovy (Engraulis encrasicolus). In both Namibia and South Africa, the numbers of Cape gannets breeding were significantly related to the biomass of epipelagic fish prey. Over the 50-y period, there was also a marked similarity in the proportions of gannets and epipelagic fish in the Benguela system, which were present in Namibia and South Africa. In the 2000s, there was an eastward shift in the distribution of sardine off South Africa and a large increase in the number of gannets breeding at South Africa's easternmost colony. When sardine were scarce off South Africa, gannets fed on anchovy, but off Namibia anchovy only temporarily and partially replaced sardine. Ecosystem management measures that might improve the conservation status of Cape gannets are considered.

scholarly journals Dive behaviour and foraging effort of female Cape fur seals Arctocephalus pusillus pusillus

2019 ◽  
Vol 6 (10) ◽  
pp. 191369 ◽  
Author(s):  
S. P. Kirkman ◽  
D. P. Costa ◽  
A.-L. Harrison ◽  
P. G. H. Kotze ◽  
W. H. Oosthuizen ◽  
...  
Keyword(s):  
Prey Species ◽  
Foraging Ecology ◽  
Critical Role ◽  
Ecosystem Structure ◽  
Depth Range ◽  
Dive Behaviour ◽  
Top Predators ◽  
Fur Seals ◽  
Cape Fur Seal ◽  
Benthic Diving

While marine top predators can play a critical role in ecosystem structure and dynamics through their effects on prey populations, how the predators function in this role is often not well understood. In the Benguela region of southern Africa, the Cape fur seal ( Arctocephalus pusillus pusillus ) population constitutes the largest marine top predator biomass, but little is known of its foraging ecology other than its diet and some preliminary dive records. Dive information was obtained from 32 adult females instrumented with dive recorders at the Kleinsee colony (29°34.17′ S, 16°59.80′ E) in South Africa during 2006–2008. Most dives were in the depth range of epipelagic prey species (less than 50 m deep) and at night, reflecting the reliance of Cape fur seals on small, vertically migrating, schooling prey. However, most females also performed benthic dives, and benthic diving was prevalent in some individuals. Benthic diving was significantly associated with the frequency with which females exceeded their aerobic dive limit. The greater putative costs of benthic diving highlight the potential detrimental effects to Cape fur seals of well-documented changes in the availability of epipelagic prey species in the Benguela.

Using a mandible accelerometer to study fine-scale foraging behavior of free-ranging Antarctic fur seals

2011 ◽  
Vol 28 (2) ◽  
pp. 345-357 ◽  
Author(s):  
Takashi Iwata ◽  
Kentaro Q. Sakamoto ◽  
Akinori Takahashi ◽  
Ewan W. J. Edwards ◽  
Iain J. Staniland ◽  
...  
Keyword(s):  
Foraging Behavior ◽  
Fine Scale ◽  
Fur Seals ◽  
Free Ranging ◽  
Antarctic Fur Seals

scholarly journals First report of lionfish prey from Western Florida waters as identified by DNA barcoding

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9922 ◽  
Author(s):  
Carlos A. Santamaria ◽  
James Locascio ◽  
Taylor M. Greenan
Keyword(s):  
Dna Barcoding ◽  
Regional Differences ◽  
Prey Species ◽  
Fish Prey ◽  
Crustacean Species ◽  
First Report ◽  
Eastern Gulf Of Mexico ◽  
Coi Barcoding ◽  
Coi Sequences ◽  
Prey Items

DNA barcoding was used to identify prey fragments recovered from the stomachs of lionfish harvested during the 2016 Sarasota Lionfish Derby. A total of 305 prey fragments were recovered from 50 stomachs (mean = 4.6 per stomach), of which 184 (60.3%) fragments could be identified to either species or genus when Cytochrome Oxidase I (COI) sequences were queried against the Barcode of Life Database. We identified 21 fish prey species which represented fourteen families and accounted for 95.7% of genetically identifiable prey items. The remaining prey items identified corresponded to six crustacean species. The four most common prey taxa in lionfish stomachs were Ptereleotris calliura (24.3%), an unidentified Microgobius species (20.4%), Diplectum formosum (14.3%), and Apogon aurolineatus (12.2%). The most frequently observed crustacean species, Metapenaeopsis goodei, was found in only three stomachs (6.1%). We also report eleven taxa as putative novel lionfish prey species, most of which are common in Florida waters. Sixteen prey items were identified as lionfish (P. volitans); however, it was not definitive whether these detections were due to cross contamination or cannibalization. This represents the first report of lionfish diets from Florida waters in the Eastern Gulf of Mexico based on barcoding efforts. Our results are largely congruent with previous COI barcoding based studies of lionfish diets, indicating these predators to be generalists exhibiting preferences for specific prey traits but with regional differences in their diets.

Spring and summer predation on fish by the Antarctic fur seal, Arctocephalus gazella, at King George Island, South Shetland Islands

1999 ◽  
Vol 77 (7) ◽  
pp. 1157-1160 ◽  
Author(s):  
G A Daneri ◽  
A R Carlini
Keyword(s):  
Fish Species ◽  
Relative Proportion ◽  
South Shetland Islands ◽  
Arctocephalus Gazella ◽  
King George Island ◽  
Pleuragramma Antarcticum ◽  
Fish Prey ◽  
Austral Spring ◽  
Shetland Islands ◽  
Fur Seals

The fish component of the diet of nonbreeding male Antarctic fur seals, Arctocephalus gazella, was analyzed from 70 scats collected at Stranger Point, King George Island, South Shetland Islands, during the austral spring (n = 36) and summer (n = 34) of 1993-1994. Fish occurred in approximately 70% of scats that contained food remains irrespective of season. In spring, the main fish prey were Electrona antarctica, Pleuragramma antarcticum, and Notolepis coatsi, which together gave two-thirds of the 110 otoliths recovered. In summer, 457 otoliths were retrieved; the most frequent and abundant species were Gymnoscopelus nicholsi, E. antarctica, and P. antarcticum, which represented over 80% of the otoliths recovered. A substantial increase in the amount of fish ingested by fur seals occurred from spring to summer concomitant with a change in the relative proportion of fish taxa. Most fish species identified are pelagic and feed on krill. During the study period, commercial fishing in the area was not based upon any of the fish species identified.

The diet of itinerant male Hooker's sea lions, Phocarctos hookeri, at sub-Antarctic Macquarie Island

1999 ◽  
Vol 26 (6) ◽  
pp. 839 ◽  
Author(s):  
Clive R. McMahon ◽  
Dave Holley ◽  
Susan Robinson
Keyword(s):  
Teleost Fish ◽  
Prey Species ◽  
Abundant Species ◽  
Primary Component ◽  
Faunal Remains ◽  
Macquarie Island ◽  
Sea Lions ◽  
Fur Seals ◽  
Prey Items ◽  
Phocarctos Hookeri

Scats were collected from itinerant male Hooker's sea lions, Phocarctos hookeri, at Macquarie Island and the uneroded faunal remains used to assess the diet. Uneroded sagittal otoliths were used to identify teleost fish and to calculate fish size. Prey items included 14 taxa of teleost fish, cephalopods, gastropods, crustaceans and fur seals. Fish constituted the primary component of the diet. Prey species previously uncommon in the diet of seals and penguins around Macquarie Island were commonly eaten by Hooker's sea lions. The sub-Antarctic horse fish (Zanclorhynchus spinifer) and the Patagonian tooth fish (Dissostichus eleginoides) were the two most abundant species and occurred in 62.5% and 41.7% of all scats respectively. There were no age-specific and individual differences in the diet of sea lions. Seasonal variances in diet were absent. Small plastic fragments (diameter ∼1 mm) were found only in association with otoliths of Electrona subaspera. Some overlap was seen between the diet of itinerant male Hooker's sea lions and the commercial fisheries that currently operate around Macquarie Island.

Changes in nesting-habitat use of large gulls breeding in Witless Bay, Newfoundland

2001 ◽  
Vol 79 (12) ◽  
pp. 2159-2167 ◽  
Author(s):  
Gregory J Robertson ◽  
David Fifield ◽  
Melanie Massaro ◽  
John W Chardine
Keyword(s):  
Reproductive Output ◽  
Prey Species ◽  
No Reduction ◽  
Breeding Habitat ◽  
Larus Argentatus ◽  
Herring Gull ◽  
Fish Prey ◽  
Oceanodroma Leucorhoa ◽  
Herring Gulls ◽  
Capelin Mallotus Villosus

We counted herring gull (Larus argentatus) and great black-backed gull (Larus marinus) nests in the Witless Bay Seabird Ecological Reserve in southeastern Newfoundland, Canada, in 1999 and 2000 and compared our results with previous nest counts from the 1970s. On Gull Island, herring gull nest numbers were 27.5% (1999) and 30.0% (2000) lower than in 1979. Similarly, on Great Island, by 2000 the numbers of herring gull nests had declined 40.8% from numbers in 1979. Counts of great black-backed gull nests were more variable, but suggest a slight or no reduction since 1979. Numbers of herring gulls nesting in rocky and puffin-slope habitats were much reduced (50–70%), while numbers nesting in meadows and forests have actually increased since the 1970s. Great black-backed gulls showed a similar change in nesting distribution. For herring gulls, these changes in nesting numbers matched differences in reproductive success previously documented in these habitats. We suggest that the decline in gull numbers and the change in breeding-habitat selection were caused by changes in the food availability for gulls. Reduced amounts of fisheries offal and the delayed arrival onshore of capelin (Mallotus villosus), an important fish prey species for gulls, have all likely led to the decline in gull reproductive output. Gulls nesting in meadows and forests may be maintaining adequate reproductive output by focusing on alternative prey, such as adult Leach's storm-petrels (Oceanodroma leucorhoa), rather than scarce refuse and fish.

scholarly journals Fish prey of the sympatric Galápagos fur seals and sea lions: seasonal variation and niche separation

1999 ◽  
Vol 77 (8) ◽  
pp. 1204-1216 ◽  
Author(s):  
Thomas Dellinger ◽  
Fritz Trillmich
Keyword(s):  
El Niño ◽  
El Nino ◽  
Warm Season ◽  
Niche Overlap ◽  
Sympatric Species ◽  
Niche Separation ◽  
Fish Prey ◽  
Sea Lions ◽  
Fur Seals ◽  
Fur Seal

Analysis of fish otoliths in scats and vomits of Galápagos fur seals (Arctocephalus galapagoensis) and Galápagos sea lions (Zalophus californianus wollebaeki) was used to determine the numerical composition of the diets for the post-El Niño year 1983, the cold seasons in 1984 and 1985, and the warm season in 1986. Between 84 and 99% of all otoliths in fur seal scats were from myctophids and bathylagids. The fur seals' diet included 26 species. Only 3 species contributed more than 1% of otoliths. No seasonal differences in diet were found. Sea lion samples contained a mean of 14 otoliths. Sardines (Sardinops sagax) contributed 75-85% of otoliths. Sea lions preyed on 24 species, but only 3 surpassed 1% abundance. Seasonality was not reflected in the sea lions' diet. After the 1982-1983 El Niño, the diets of both species deviated from those in all other years of the study. Food-niche overlap between the two sympatric species was almost non-existent. This is hard to understand, based on our knowledge of the diving capabilities of the two species, but reflects the fact that Galápagos fur seals are nighttime foragers and sea lions are daytime foragers.

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