Cape cormorants decrease,move east and adapt foraging strategies following eastward displacement of their main prey     

RJM Crawford  RM Randall  TR Cook  PG Ryan  BM Dyer  R Fox 《African Journal of Marine Science》2016,38(3):373-383

Numbers of Cape cormorants Phalacrocorax capensis breeding in South Africa decreased by nearly 50% from approximately 107 000 pairs in 1977–1981 to 57 000 pairs in 2010–2014. Although four colonies had >10 000 pairs in 1977–1981, there was just one such colony in 2010–2014. Almost all the decrease occurred after the early 1990s off north-west South Africa, between the Orange River estuary and Dassen Island. South of this, the number breeding in the two periods was stable, with some colonies being formed or growing rapidly in the 2000s. The proportion of South Africa’s Cape cormorants that bred south of Dassen Island increased from 35% in 1977–1981 to 66% in 2010–2014, with the opposite situation observed in the north-west. This matched a shift to the south and east in the distributions of two of the Cape cormorant’s main prey species, anchovy Engraulis encrasicolus and sardine Sardinops sagax. In 2014, an apparent scarcity of prey in the north-west resulted in Cape cormorants attempting to take bait from hooks of fishing lines over an extended period, a behaviour not previously recorded. The number of Cape cormorants breeding in the south may be constrained by the absence of large islands between Dyer Island in the west and Algoa Bay in the east. If so, it may be possible to bolster the southern population through the provision of appropriate breeding habitat, such as platforms, or restricting human disturbance at suitable mainland cliff breeding sites.  相似文献   

A contribution to the migration of gold in the biosphere of the humid mild zone     

J. Kaspar  I. Hudec  P. Schiller  G. B. Cook  A. Kitzinger  E. W  lfl 《Chemical Geology》1972,10(4):299-305

The content of gold in plants has been used as an indicator in the prospecting for gold. For this purpose non-destructive analytical methods have been developed. In the humid mild zone — where the process of weathering is of a kaolinitic character — there is practically no migration of gold, and consequently its increased content indicates the presence of a gold deposit.  相似文献   

Radiometry and crystallization history of the Buchanan granite massif, Texas, USA     

Beverly Gatlin Cook  John J.W. Rogers 《Lithos》1968,1(4):398-407

  相似文献   

The influence of tidal flushing, light exposure and natant macrofauna on edaphic chlorophyll a in a Louisiana salt marsh     

Stephen A. Whipple  John W. Fleeger  Lawrence L. Cook 《Estuarine, Coastal and Shelf Science》1981,13(6):637-643

  相似文献   

The implications of warming climate for the management of North Sea demersal fisheries   总被引：3，自引：0，他引：3  

Cook  R.M.; Heath  M.R. 《ICES Journal of Marine Science》2005,62(7):1322-1326

  相似文献   

Trial of a tractor dredger for cockles in Burry Inlet, South Wales     

Cotter  A. J. R.; Walker  P.; Coates  P.; Cook  W.; Dare  P. J. 《ICES Journal of Marine Science》1997,54(1):72-83

  相似文献   

UV observations of macrospicules at the solar limb     

K. P. Dere  J.-D. F. Bartoe  G. E. Brueckner  J. W. Cook  D. G. Socker  J. W. Ewing 《Solar physics》1989,119(1):55-63

During the Spacelab 2 mission, the NRL High Resolution Telescope and Spectrograph (HRTS) obtained a time-series of broad-band ultraviolet images of macrospicules at the solar limb inside a polar coronal hole with a temporal resolution of 20 and 60 s. The properties of the macrospicules observed in the Spacelab data are measured and compared with the properties reported for EUV macrospicules observed during Skylab (Bohlin et al., 1975; Withbroe et al., 1976). There is a general agreement between the data sets but several differences. Because of the higher temporal resolution of the Spacelab data, it is possible to see macrospicules with shorter lifetimes than seen during Skylab, as well as variations on faster timescales. The largest (30–60) and fastest (150 km s ^-1) macrospicules seen during Skylab were not found in the Spacelab observations. The Spacelab data support the conclusion that many macrospicules decay by simply fading away.  相似文献   

The relationship between African easterly waves and daily rainfall over West Africa: observations and regional climate simulations     

Julien Crétat  Edward K. Vizy  Kerry H. Cook 《Climate Dynamics》2015,44(1-2):385-404

  相似文献   

Sex change and morphological transitions in a marine ectoparasite          下载免费PDF全文

Colt Cook  Pablo Munguia 《Marine Ecology》2015,36(3):337-346

The fitness of parasitic organisms is strongly driven by their ability to infect potential hosts. Although transmission to a host organism is a key component to the parasitic lifestyle, surviving and reproducing within a host poses additional challenges. Cymothoa excisa is a parasitic isopod that infects Atlantic croaker, Micropogonias undulatus, along the Texas coast and has evolved mechanisms to successfully survive and reproduce within its host. Cymothoa excisa is known to exhibit sex‐change strategies but limited information exists on morphological changes, reproductive output and the timing at which sex change becomes optimal. This study collected Atlantic croaker during a 22‐month survey period and identified parasite prevalence and intensity in the host fish population. Infection rates were constant throughout the year at 19.88% and intensity increased through the season up to a maximum of four parasites. Following collection, isopod morphological parameters were quantified for each life stage (including female, transitional, male and juvenile), identifying shape and size transitions through ontogeny and sex change. Transitional C. excisa isopods only occurred when only one isopod was present in a fish, suggesting that isopods change sex from male to female if they are the first to recruit to an uninfected host. As isopods transition to females they have a large increase in size, legs, and pleotelson (which influence fecundity and anchoring ability), whereas the gonopod, eyes and uropod show a reduction (which are no longer needed for swimming and finding hosts). Data suggest that C. excisa sex change is related to the timing of infection and brood size increases with female size and host size. Therefore, it would be advantageous to be the first isopod to infect a host, as it could change into a female and increase reproductive potential. We discuss hypotheses that could explain the mating behavior of parasitic isopods.  相似文献   

Environmental tolerance of Caprella mutica: implications for its distribution as a marine non-native species     

Ashton GV  Willis KJ  Burrows MT  Cook EJ 《Marine environmental research》2007,64(3):305-312

Physiological tolerances limit the distribution of marine species, with geographical ranges being set by environmental factors, such as temperature and salinity, which affect the rates of vital processes and survival of marine ectotherms. The physiological tolerances of the non-native marine amphipod Caprella mutica were investigated in laboratory experiments. Adult C. mutica were collected from a fish farm on the west coast of Scotland and exposed to a range of temperatures and salinities for 48 h. C. mutica were tolerant of a broad range of temperature and salinity conditions, with 100% mortality at 30 degrees C (48 h LT50, 28.3+/-0.4 degrees C), and salinities lower than 16 (48 h LC50, 18.7+/-0.2). Although lethargic at low temperatures (2 degrees C), no mortality was observed, and the species is known to survive at temperatures as low as -1.8 degrees C. The upper LC(50) was greater than the highest salinity tested (40), thus it is unlikely that salinity will limit the distribution of C. mutica in open coastal waters. However, the species will be excluded from brackish water environments such as the heads of sea lochs or estuaries. The physiological tolerances of C. mutica are beyond the physical conditions experienced in its native or introduced range and are thus unlikely to be the primary factors limiting its present distribution and future spread.  相似文献