Evaluation of food competition and resource partitioning of recruiting fish with permanent residents in a seagrass habitat     

Craig A. Meakin 《新西兰海洋与淡水研究杂志》2020,54(2):149-166

ABSTRACT

Recruiting King George whiting Sillaginodes punctatus were studied to assess the potential for food competition with permanent resident fish species in a nursery habitat. Marine migrant post larval S. punctatus (<60?mm TL) consumed primarily harpacticoid copepods and had high (>0.6) diet overlap with permanent resident fish species Favonigobius leteralis and Stigmatopora nigra. Food electivity index indicated that S. punctatus juveniles preferred harpacticoid copepods and amphipods, while juvenile Heteroclinus adelaide and Gymnapistes marmoratus migrating to the nursery habitat targeted larger prey such as amphipods. Preference for larger prey by H. adelaide and G. marmoratus species coupled with differences in prey composition in the stomach was due to mouth size and feeding habits, resulting in different food preferences to S. punctatus. The whiting showed an ontogenetic shift in diet with early settlers (>60?mm TL) consuming less copepods and more amphipods, while previous year recruits (>120?mm TL) consumed polychaete worms. This study indicates that competition for food resources between the new recruiting S. punctatus juveniles and permanent resident juveniles is reduced through differences in temporal and spatial feeding behaviours, mouth morphology, and ontogenetic shift in prey consumption.  相似文献   

Community structure of infaunal macrobenthos around vestimentiferan thickets at the San Clemente cold seep,NE Pacific     

Angelo F. Bernardino  Craig. R. Smith 《Marine Ecology》2010,31(4):608-621

The San Clemente cold seep lies within 100–200 km of other reducing habitats in the NE Pacific, offering an opportunity to compare diversity and species overlap among reducing habitats (i.e. whale‐, kelp‐, and wood‐falls) at similar depths within a single region. Video observations from the research submersible Alvin at the San Clemente seep (1800 m depth) indicated clumps (‘thickets’) of vestimentiferans distributed as meter‐scale patches interspersed with vesicomyid clam beds and black sediments. Sediment‐core samples were collected at distances of 0 to 80–200 m along randomly oriented transects radiating outward from vestimentiferan thickets to evaluate changes in macrofaunal community structure from thickets into the background community. Macrofaunal abundance was elevated at distances of 0–1 m compared to 80–200 m (i.e. the ‘background’ community). The tube‐building frenulate worms Siboglinum spp., along with peracarid crustaceans, dominated sediments within 1 m of vestimentiferan thickets. Species diversity was depressed within 1 m of thickets but with high rates of species accumulation, suggesting that seep sites greatly increase sediment heterogeneity and facilitate colonization by non‐background macrofaunal species. Stable isotope data indicate chemosynthetic nutrition for some dominant macrofaunal species within 1 m of tubeworm thickets. The macrofaunal community near vestimentiferan thickets in San Clemente seep contains intermediate levels of species richness and diversity compared to other deep‐sea seep areas in the northeast Pacific. There was low species overlap between the San Clemente seep macrofauna and communities in reducing habitats near wood‐, whale‐, and kelp‐falls at similar depths within the region, suggesting that seeps harbor a distinct infaunal community.  相似文献   

The impact of scour processes on a smothered reef system in the Irish Sea     

Alexander Callaway  Jennifer Smyth  Craig J. Brown  Rory Quinn  Matthew Service  David Long 《Estuarine, Coastal and Shelf Science》2009,84(3):409-422

The Irish Sea, like many marine areas, is threatened by anthropogenic activities. In particular the Pisces Reef system, a series of smothered rocky reefs are subject to fishing pressures as a result of their position within a Nephrops norvegicus fishery. In an area of sediment deposition and retention the reefs modify the environment by increasing the energy of near-bottom currents which results in localised scouring. This is the first study to attempt to characterise and investigate the ecological functioning of the Pisces Reef system. A multidisciplinary approach was essential for accurate investigation of the area. To facilitate more effective management of the benthic habitats of the Reef system, this study integrates acoustic, seismic, grab sampling and video ground-truthing methods for benthic habitat discrimination. Orientation of the scour hollows also suggest that seabed features could be used to infer dominant flow regimes such as the Irish Sea Gyre. The data revealed significant geology–benthos relationships. A unique biotope was described for the reef habitat and it was demonstrated that scouring may influence community composition through disturbance mechanisms. This study provides preliminary information required for management of a unique habitat within a uniform region.  相似文献   

Groundwater-level response to land-use change and the implications for salinity management in the West Moorabool River catchment, Victoria, Australia   总被引：1，自引：1，他引：0  

Peter G. Dahlhaus  Timothy J. Evans  Erica L. Nathan  Jim W. Cox  Craig T. Simmons 《Hydrogeology Journal》2010,18(7):1611-1623

The connection between the removal of native vegetation, rising water tables and increasing stream salinity has been established for many catchments across Australia. However, the West Moorabool River in south west Victoria is an example of a catchment where there has been little discernable effect on groundwater levels following land clearing. Over the past 150 years, a significant portion of the catchment has been cleared of dense forest for agricultural development. Historic standing water-level records from 1870–1871 and 1881 are compared with contemporary measurements (1970s to 2007) recorded in the government bore databases. The data show that the earliest recorded groundwater levels are well within the seasonal range of values observed today. By integrating geology and hydrogeology with historical observations of groundwater levels, climate data and land use, the contemporary field observations of stream salinity are linked to the changed water use and shift in rainfall. In contrast to the normally accepted axiom, reafforestation as a management strategy to mitigate the rising salinity in the West Moorabool River catchment would seem inappropriate.  相似文献   

Suspended sediment transport regime in a debris‐flow gully on Vancouver Island,British Columbia     

Craig J. Nistor  Michael Church 《水文研究》2005,19(4):861-885

In debris‐flow‐prone channels, normal fluvial sediment transport occurs (nearly exclusively in suspended mode) between episodic debris‐flow events. Observations of suspended sediment transport through a winter season in a steepland gully in logged terrain revealed two event types. When flows exceeded a threshold of 270 l s⁻¹, events yielded significant quantities of sediment and suspended sediment concentration increased with flow. Smaller events were strongly ‘supply limited’; sediment concentration decreased as flow increased. Overall, there is no consistent correlation between runoff and sediment yield. Within the season, three subseasons were identified (demarcated by periods of freezing weather) within which a pattern of fine sediment replenishment and evacuation occurred. Finally, a signature of fine sediment mobilization and exhaustion was observed within individual events. Fine sediment transport occurred in discrete pulses within storm periods, most of the yield occurring within 5 to 15% of storm runoff duration, so that it is unlikely that scheduled sampling programs would identify significant transport. Significant events are, however, generally forecastable on the basis of regional heavy rainfall warnings, providing a basis for targeted observations. Radiative snowmelt events and rain‐on‐snow remain difficult to forecast, since the projection of temperatures from the nearest regular weather station yields variable results. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

An introduction to sustainable development – By Peter R. Rogers, Kazi F. Jalal and John A. Boyd     

John L. Craig 《New Zealand geographer》2010,66(1):96-96

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The Electrical Resistivity of the Vadose Zone — Field Survey     

Reinhard K. Frohlich  Craig D. Parke 《Ground water》1989,27(4):524-530

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He,Sr and Nd isotopic variations in lavas from the juan fernandez archipelago,SE pacific     

K. A. Farley  A. R. Basu  H. Craig 《Contributions to Mineralogy and Petrology》1993,115(1):75-87

Helium, Sr, and Nd isotopic ratios and major and trace element compositions have been measured on a suite of lavas from the intra-plate volcanos of the Juan Fernandez Archipelago, Chile. Lavas from the islands of Mas Afuera and Mas a Tierra and from Monte Alpha and Friday seamounts have Sr and Nd isotopic ratios lying on the low¹⁴³Nd/¹⁴⁴Nd side of the mantle array (⁸⁷Sr/⁸⁶Sr:0.7034–0.7037;¹⁴³Nd/¹⁴⁴Nd:0.51281–0.51289). The homogeneity of these tracers suggests the involvement of a restricted range of mantle source compositions throughout Juan Fernandez volcanism. In marked contrast is the large range in³He/⁴He, from 7.8 to 18.0 R_A. A bimodal³He/⁴He distribution on Mas a Tierra is associated with two distinct volcanic lineages;³He/⁴He ratios of 14.5–18.0 R_A (n=15) occur in alkalic and tholeiitic shield basalts, whereas post-shield basanites range from 11.2 to 13.6 R_A (n=12). Elemental and isotopic systematics demonstrate a transition from an enriched (Loihi-like) plume source in the shield lavas to a more MORB-like source in the post-shield volcanics. The transition between these sources is much more pronounced in³He/⁴He than in the other isotopic tracers. The predominantly tholeiitic basalts of Mas Afuera have exceptionally uniform isotopic and elemental characteristics; Sr and Nd ratios are similar to those of Mas a Tierra, but³He/⁴He ratios are lower and more uniform at 8.3±0.5 R_A (n=17). The dramatic distinction between Mas Afuera and Mas a Tierra helium is surprising given the great similarity between the two islands in other geochemical characteristics. Both the Mas Afuera and Mas a Tierra results demonstrate that helium records systematic processes not readily apparent from other isotopic or elemental indicators. Neither magma chamber degassing nor local metasomatic events are likely to be responsible. We suggest that the observed variations may be attributed to mixing of plume and asthenospheric sources in which the plume component is characterized by a heterogeneous distribution of volatiles or has suffered extraction of small degree partial melts prior to mixing.  相似文献   

A Raman spectroscopic study of H/D isotopically substituted hydrous aluminosilicate glasses     

Paul F. McMillan  Brent T. Poe  Thomas R. Stanton  Richard L. Remmele 《Physics and Chemistry of Minerals》1993,19(7):454-459

We have obtained high quality Raman spectra for two H/D isotopically substituted hydrous aluminosilicate glasses with compositions along the NaAlSi₃O₈-SiO₂ join. Consistent with the results of previous studies, the isotope shift for the band near 900 cm^–1, whose intensity grows with increasing water content, is extremely small: v _h /v _d = 1.004 ± 0.004. The lack of a definite H/D isotope shift for this band does not, however, preclude its association with a vibration of a hydrous species in the glass, because of likely strong coupling between different vibrational modes of hydrated framework species. The 900 cm^–1 band could well be due to a T — OH (T = Si, Al) stretching or bending vibration in the hydrous glass, as required by the presence of a combination band near 4500 cm^–1 in near-infrared spectra.  相似文献   

Inheritance of smolting phenotypes in backcrosses of hybrid stream-type × ocean-type chinook salmon (Oncorhynchus tshawytscha)     

W. Craig Clarke  Ruth E. Withler  John E. Shelbourn 《Estuaries and Coasts》1994,17(1):13-25

Chinook salmon (Oncorhynchus tshawytscha) are ecologically and geographically differentiated into two life history types: “ocean-type,” which enter estuaries as fry or fingerlings in the first year of life and rear there for up to 6 wk before migrating to sea, and “stream-type,” which migrate seaward as smolts after one or more years in fresh water and are only transient residents in the outer portion of estuaries. Following exposure to a long-day priming photoperiod for 2 mo from the time of first feeding, progeny of stream-type chinook salmon undergo a reduction in growth during summer and remain as parr, whereas progeny of ocean-type chinook salmon and hybrids continue to grow during the summer and develop into underyearling smolts. Male purebred and hybrid F₁ progeny of ocean-type and stream-type chinook salmon were backcrossed to females of both parental populations to examine the segregation of photoperiod-independent (smolt) and photoperiod-dependent (parr) phenotypes among progeny. Results of the backcrosses of the hybrid F₁ males depended on female type. The backcross to ocean-type females produced progeny that were predominantly smolts, whereas progeny from the backcross to stream-type females segregated into approximately equal numbers of smolts and parr. These results are consistent with Mendelian inheritance of a single major gene with two alleles: a dominant allele for the photoperiod-independent phenotype of ocean-type chinook salmon and a recessive allele for the photoperiod-dependent phenotype of stream-type chinook salmon.  相似文献