Diet of the South African fur seal (1974–1985) and an assessment of competition with fisheries in southern Africa

David, J. H. M.

doi:10.2989/025776187784522568

Cited by 64 publications

(68 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This attitude perpetuates the misbelief that culls of fur seals would reduce competition because fewer seals would eat fewer fish, and the surfeit of fish would become available for commercial exploitation (Bonner 1982;Butterworth et al 1988;Harwood & Croxall 1988;Crawford et al 1992;Lavigne 1992;Meyer et al 1992;Wickens et al 1992a,b;Bowen 1997;. Although fur seals are conspicuous as top predators, their impact on fish stocks has been overemphasised (David 1987;Crawford et al 1992;Harwood 1992;Lavigne 1992;Wickens et al 1992b). Instead, the bulk of fish mortality is attributable to other predatory fish and the impact of marine mammals is relatively low (DeMaster & Sisson 1992;Wickens et al 1992b;.…”

Section: Worldwide Pinniped-fisheries Interactionsmentioning

confidence: 99%

Folklore and chimerical numbers: Review of a millennium of interaction between fur seals and humans in the New Zealand region

Lalas¹,

Bradshaw

2001

New Zealand Journal of Marine and Freshwater Research

View full text Add to dashboard Cite

The increase in numbers and range expansion of New Zealand fur seals (Arctocephalus forsteri Lesson) in the New Zealand region has prompted many people to comment on their effects on the marine and coastal environments. Overall there are anomalies in the data describing the distribution and abundance of fur seals in the New Zealand region, and there is a need for a better understanding of the interactions with humans and the impacts on the New Zealand environment. The distribution resulting from the present pattern of re-colonisation differs from the perception of their distribution before decimation by humans. We hypothesise that the pristine distribution was temperate rather than subantarctic. Previously published records which have documented changes in the abundance and distribution of the species are shown to be wanting. The most controversial management issue is interaction with commercial fisheries where we conclude that neither of the Corresponding author. Received 21 April 1999; accepted 20 November 2000 extreme options, culling of seals nor closure of some fishing grounds, is justified. Other issues addressed include tourism, te tikanga Maori o mahinga kai (the customary use of wildlife by Maori), and impact of fur seals on the coastal environment. This species offers a rare and exciting opportunity to test the theoretical processes of population expansion that can be investigated as a natural experiment. We suggest that the current management policy should remain unchanged until the current paucity of information on the degree of interaction between fur seals and humans has been addressed. M99022

show abstract

Section: Worldwide Pinniped-fisheries Interactionsmentioning

confidence: 99%

Folklore and chimerical numbers: Review of a millennium of interaction between fur seals and humans in the New Zealand region

Lalas¹,

Bradshaw

2001

New Zealand Journal of Marine and Freshwater Research

View full text Add to dashboard Cite

show abstract

“…The diet of Cape fur seals has been determined from stomach contents of animals shot at sea (Rand 1959, David 1987, Kirkman et al 2007b) and, since the mid-1990s, in the NB through analysis of hard prey remains in seal scats (De Bruyn et al 2003, 2005, Mecenero et al 2006a, Kirkman et al 2007a. For the SB we have used diet composition estimates from the west coast in the 1950s (Rand 1959) and, since 1980, data reanalyzed and updated by Kirkman et al (2007b).…”

Section: Trophic Interactions Between Predators and Their Preymentioning

confidence: 99%

“…For the SB we have used diet composition estimates from the west coast in the 1950s (Rand 1959) and, since 1980, data reanalyzed and updated by Kirkman et al (2007b). For the NB in the 1980s, we used results from stomach contents collected between 1980 and 1984 (David 1987) and estimates from scat analysis calculated independently for four different subregions (J-P Roux unpubl data) and then weighted those estimates according to estimates derived from aerial surveys of fur-seal populations breeding in each subregion (Kirkman et al 2007c). In the SB, estimates of Cape fur seal diet energy density ranged between 5.22 kJ g −1 in the 1950s and 5.76 kJ g −1 in the more recent period (Fig.…”

Section: Trophic Interactions Between Predators and Their Preymentioning

confidence: 99%

Jellyfication of Marine Ecosystems as a Likely Consequence of Overfishing Small Pelagic Fishes: Lessons from the Benguela

Roux¹,

Lingen²,

Gibbons³

et al. 2013

BMS

128

View full text Add to dashboard Cite

Changes in two contrasting ecosystems of the Benguela upwelling region, one dominated at mid-trophic level by jellyfishes (Namibia, northern Benguela ecosystem, where small pelagic fish abundance has been severely depleted) and one still dominated by small pelagic fishes (South Africa, southern Benguela) were compared in an effort to determine ecosystem trajectories under different exploitation regimes. The role of small pelagic fishes (clupeoids) was highlighted in the context of their importance in maintaining interactions in marine ecosystems. In particular, we examined trophic cascades and possible irreversible changes that promote the proliferation of jellyfishes in marine systems. We found that the presence of large populations of small pelagic fishes has a fundamental role in preserving beneficial trophic interactions in these marine ecosystems. The implications of trophic cascades, such as those observed in the northern Benguela, for ecosystem-based management were apparent. In addition, this comparison provides contrasting case studies to inform the development of management scenarios that avoid ecosystem shifts that affect predators and reduce the value of fisheries production.

show abstract

“…Algoa Bay also hosts important populations of marine top predators, such as South African fur seals, bottlenose and common dolphins, cape gannets and the world's largest African penguin colony (Pichegru et al 2010), which feed predominantly on small pelagic fish (Batchelor and Ross 1984;David 1987;Young and Cockcroft 1994). Moreover, there is an ongoing discussion about the potential impacts that the prospective finfish farming activity planned in Algoa Bay (Bloom 2012;Hutchings et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Influence of environmental variables on the larval stages of anchovy, Engraulis encrasicolus, and sardine, Sardinops sagax, in Algoa Bay, South Africa

et al. 2017

View full text Add to dashboard Cite

We investigated the environmental drivers of larval abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax in Algoa Bay, Eastern Cape (South Africa). This study comprised a predrought post-drought time period, comparing the responses of the fish larvae to different factors before and after the drought. The current study presents, for the first time, which environmental variables are affecting the anchovy and sardine larvae populations in the region. Easterly wind speed and zooplankton density were the only environmental variables that presented a significant change between the pre-and post-drought periods, increasing after the drought. Generalized additive models (GAMs) were used in order to explore the effects that environmental factors might have in the abundance of anchovy and sardine larvae in Algoa Bay. Specifically, the GAM that best explained the deviance of the anchovy larvae dynamics included the covariates rainfall, easterly wind speed, Chl a concentration, sardine larvae abundance and the interactions SST*Chla and sard*SST. The GAM best explaining sardine larvae abundance included only the easterly wind speed as a covariate. This model showed that there was a positive relationship between the higher values of wind speed and sardine larvae abundance.

show abstract

Diet of the South African fur seal (1974–1985) and an assessment of competition with fisheries in southern Africa

Cited by 64 publications

References 4 publications

Folklore and chimerical numbers: Review of a millennium of interaction between fur seals and humans in the New Zealand region

Folklore and chimerical numbers: Review of a millennium of interaction between fur seals and humans in the New Zealand region

Jellyfication of Marine Ecosystems as a Likely Consequence of Overfishing Small Pelagic Fishes: Lessons from the Benguela

Influence of environmental variables on the larval stages of anchovy, Engraulis encrasicolus, and sardine, Sardinops sagax, in Algoa Bay, South Africa

Contact Info

Product

Resources

About