Field Methods

and, K. L. Hemingway; Elliott, Matthew

doi:10.1002/9780470995228.ch8

Cited by 12 publications

(12 citation statements)

References 99 publications

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“…densities seemed also lower, comparing with Phil and Rosenberg's (1982) results (Table 2). The catch efficiency of the sampling gear (beam trawl) used in the present study has been widely assumed to be 30% (Hemingway and Elliott, 2002), but even if the density and production values were multiplied by a factor (3.3333) they would still be lower. Besides possible inaccuracies in determining population sizes and their changes, fish production estimates are subjected to other sources of error: different effects of mortality, emigration and immigration to the estuary (Costa et al, 2002;Cowley and Whitfield, 2002), different growth rates along the life cycle, as seen by Fouda and Miller (1981) for Pomatoschistus microps, and different methods to estimate production (Costa et al, 2002).…”

Section: Species Temporal Dynamics and Productionmentioning

confidence: 99%

Strategies of Pomatoschistus minutus and Pomatoschistus microps to cope with environmental instability

Dolbeth

Martinho

Leitão

et al. 2007

Estuarine, Coastal and Shelf Science

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The populations of Pomatoschistus minutus and Pomatoschistus microps were studied from June 2003 to May 2006 in the Mondego estuary, in order to understand the ability of these species to withstand environmental variability. During this period a severe drought occurred (2005), with consequent lower freshwater runoff and higher salinity incursion into the estuary. Occasional abnormal high water temperatures were observed in 2003 and 2005. The fish populations were sampled monthly along an estuarine gradient, from which population density, structure, growth and biomass production was assessed. Pomatoschistus minutus distributed mainly at the most saline downstream area, while P. microps distributed within the whole estuary, in accordance to the salinity and temperature tolerances for the species. A clear decrease in density and production was observed for P. minutus in the dry year, with non-expressive recruitments and the quick disappearance of the parental cohort. For P. microps, the decrease was not so pronounced. No direct effects were attributable to the salinity and temperatures variations (resulting from the drought and high temperatures). Yet, higher predation pressure on P. minutus hypothesis was raised, as the salinity incursion increased the piscivorous marine adventitious species in the downstream areas. Pomatoschistus microps benefited from a wider temperature and salinity range tolerance, allowing the species to occupy different areas in the estuary and by this seemed better able to cope with the environmental conditionings during the 3-year studied period.

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Section: Species Temporal Dynamics and Productionmentioning

confidence: 99%

Strategies of Pomatoschistus minutus and Pomatoschistus microps to cope with environmental instability

Dolbeth

Martinho

Leitão

et al. 2007

Estuarine, Coastal and Shelf Science

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“…Negative production values were not accounted for the overall fish estimates, which were regarded as no production. Production estimates were also presented with the correction for the catch efficiency of the sampling gear (beam trawl), which according to Hemingway and Elliott (2002) is 30%.…”

Section: Secondary Productionmentioning

confidence: 99%

Estuarine production of resident and nursery fish species: Conditioning by drought events?

Dolbeth

Martinho

Viegas

et al. 2008

Estuarine, Coastal and Shelf Science

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The production of resident (Pomatoschistus minutus and Pomatoschistus microps) and marine juvenile fish species using the Mondego estuary (central Portugal) as nursery grounds (Dicentrarchus labrax, Platichthys flesus, Solea solea), was assessed in order to: (1) understand the potential of the estuary for fish production; (2) know the production of nursery fish species likely to be exported to the coastal stocks; and (3) how anthropogenic and natural stress could influence the estimated production. C, night temperatures). The secondary production was estimated using the increment summation method, after recognition of the cohorts. Production was in general lower in the Mondego estuary when compared to other systems, which was associated to the estuary's small area (only 3.4 km 2 , less than 1/4 of area compared to other studied systems). Dicentrarchus labrax was among the most productive species. Production decreased in the drought year for all species, especially evident for D. labrax, P. minutus and P. flesus. No direct effects could be attributable to the salinity and temperature variations and to the low freshwater discharges (resulting from the drought and high temperatures), yet these were pointed as probable major reasons for the decreased production. A significant reduction (15e45% reduction in the estuarine production) was also concluded for the potential production to be exported for coastal areas by the nursery species in the drought conditions.

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“…Quantitative sampling of estuarine fish populations presents several difficulties and has been the topic of much discussion (e.g., Haedrich and Hall, 1976;Kjelson andColby, 1976, Smith et al, 1984;Horn and Allen, 1985;Moyle et al, 1986;Rozas and Minello, 1997;Hemingway and Elliott, 2002). The fish assemblages of estuaries and other nearshore habitats, unlike the benthos or plankton, comprise many different groups representing different niches and thus requiring diverse but complementary collecting methods (Hemingway and Elliott, 2002),.…”

Section: Introduction To Estuarine Systemsmentioning

confidence: 99%

“…The fish assemblages of estuaries and other nearshore habitats, unlike the benthos or plankton, comprise many different groups representing different niches and thus requiring diverse but complementary collecting methods (Hemingway and Elliott, 2002),. Each of the several subhabitats of estuaries, e.g., tidal channels, mudflats, eelgrass beds, and marsh pools, support their own suite of associated fish species in various life stages (Allen, 1982;Yoklavich et al, 1991;Valle et al, 1999;Allen et al, 2002).…”

Section: Introduction To Estuarine Systemsmentioning

confidence: 99%

“…Each of the several subhabitats of estuaries, e.g., tidal channels, mudflats, eelgrass beds, and marsh pools, support their own suite of associated fish species in various life stages (Allen, 1982;Yoklavich et al, 1991;Valle et al, 1999;Allen et al, 2002). Some types of gear are much more effective at sampling these various subhabitats and particular life stages than others (Allen et al, 2002; see review by Hemingway and Elliott, 2002). For instance, purse seines are superior for sampling and estimating densities of midwater, schooling species and large, mobile taxa.…”

Section: Introduction To Estuarine Systemsmentioning

confidence: 99%

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