scholarly journals Making up the bed: Gravel cleaning as a contribution to nase ( Chondrostoma nasus L.) spawning and recruitment success

2020 ◽  
Vol 30 (12) ◽  
pp. 2269-2283
Author(s):  
Christoffer Nagel ◽  
Melanie Mueller ◽  
Joachim Pander ◽  
Juergen Geist
Keyword(s):  
Recruitment Success ◽  
Chondrostoma Nasus

Distribution, feeding behaviour, and condition of Cape horse mackerel early life stages, Trachurus capensis, under different environmental conditions in the northern Benguela upwelling ecosystem

2014 ◽  
Vol 72 (2) ◽  
pp. 543-557 ◽  
Author(s):  
S. J. Geist ◽  
A. Kunzmann ◽  
H. M. Verheye ◽  
A. Eggert ◽  
A. Schukat ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Feeding Ecology ◽  
Environmental Conditions ◽  
Early Life ◽  
Early Life History ◽  
Horse Mackerel ◽  
Larval Phase ◽  
Recruitment Success ◽  
Wide Range ◽  
Variable Recruitment

Abstract Early life history (ELH) traits are key to understand variable recruitment success and hence the stock size of marine fish. One of the currently most puzzling ecosystems in this regard is the northern part of the Benguela Current upwelling system off Namibia. Here, populations of the formerly dominant pelagic species, sardine and anchovy, failed to recover during the last three decades after a dramatic decline. In contrast, Cape horse mackerel, Trachurus capensis, maintained a constant population size. Warming of the system and shoaling of hypoxic zones together with feedback loops within an altered foodweb are discussed to be responsible for this regime shift. In this study, we address the role of larval traits for the successful performance of the T. capensis population under the present environmental conditions with the focus on feeding ecology. We investigated seasonal variations of the geographical distribution, growth rate, feeding ecology, and nutritional condition of their ELH stages and examined relationships with water temperature, dissolved oxygen concentration, and micro-zooplankton composition. T. capensis' ELH stages showed a wide spatial and seasonal distribution, a preference for higher water temperatures (18–21°C) and presence over a wide range of dissolved oxygen concentrations (0.13–6.35 ml O2 l−1). Feeding success was high and mainly different groups of Copepoda were targeted, which were strongly size selected. The high dietary importance of micro-copepods during large parts of the larval phase indicates successful exploitation of this food source, which has increased in abundance during the last decade. It also explains observed best nutritional conditions at temperatures between 18 and 21°C, since these small copepods are commonly associated with warmer temperatures. Altogether, these traits enhance the species' probability to encounter suitable environments for the survival of their ELH stages, which is likely to lead to their high recruitment success in the northern Benguela ecosystem.

scholarly journals Coral settlement and recruitment responses to reef fish foraging and trait diversity

2021 ◽  
Author(s):  
Cher F Y Chow ◽  
Caitlin Bolton ◽  
Nader Boutros ◽  
Viviana Brambilla ◽  
Luisa Fontoura ◽  
...  
Keyword(s):  
Reef Fish ◽  
Fish Assemblages ◽  
Reef Fishes ◽  
Foraging Strategies ◽  
Coral Recruitment ◽  
Coral Settlement ◽  
Trait Divergence ◽  
Positive Effects ◽  
Recruitment Success ◽  
Trait Diversity

The process of coral recruitment is crucial to the healthy functioning of coral reef ecosystems, as well as recovery following disturbances. Fishes are key modulators of this process by feeding on algae and other benthic taxa that compete with corals for benthic space. However, foraging strategies within reef fish assemblages are highly diverse and the effect of foraging diversity on coral recruitment success remains poorly understood. Here, we test how the foraging traits of reef fishes affect coral settlement and juvenile success at Lizard Island, Great Barrier Reef. Using a multi-model inference approach incorporating six metrics of fish assemblage foraging diversity (foraging rates, trait richness, trait evenness, trait divergence, herbivore abundance, and benthic invertivore abundance), we found that herbivore abundance had positive effects on both coral settlement and recruitment success. However, foraging trait diversity had a negative effect on coral settlement but not on recruitment. Coral settlement was higher at sites with less trait diverse fish assemblages, specifically in trait divergence and richness. Moreover, these two trait diversity metrics were stronger predictors of coral settlement success compared to herbivore abundance. Our findings provide evidence that impacts mediated by fish foraging on coral juveniles can potentially be harmful during settlement, but the space-clearing effect overall remains advantageous. We show here that the variation of fish biodiversity across reefs can be a partial driver to spatially uneven patterns of coral recruitment and reef recovery.

scholarly journals Vegetation responses to season of fire in an aseasonal, fire-prone fynbos shrubland

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3591 ◽  
Author(s):  
Tineke Kraaij ◽  
Richard M. Cowling ◽  
Brian W. van Wilgen ◽  
Diba R. Rikhotso ◽  
Mark Difford
Keyword(s):  
Floristic Composition ◽  
Fire Season ◽  
Summer Drought ◽  
Winter Rainfall ◽  
Recruitment Success ◽  
Floral Diversity ◽  
Four Seasons ◽  
Different Seasons ◽  
Varied Response ◽  
One Year

Season of fire has marked effects on floristic composition in fire-prone Mediterranean-climate shrublands. In these winter-rainfall systems, summer-autumn fires lead to optimal recruitment of overstorey proteoid shrubs (non-sprouting, slow-maturing, serotinous Proteaceae) which are important to the conservation of floral diversity. We explored whether fire season has similar effects on early establishment of five proteoid species in the eastern coastal part of the Cape Floral Kingdom (South Africa) where rainfall occurs year-round and where weather conducive to fire and the actual incidence of fire are largely aseasonal. We surveyed recruitment success (ratio of post-fire recruits to pre-fire parents) of proteoids after fires in different seasons. We also planted proteoid seeds into exclosures, designed to prevent predation by small mammals and birds, in cleared (intended to simulate fire) fynbos shrublands at different sites in each of four seasons and monitored their germination and survival to one year post-planting (hereafter termed ‘recruitment’). Factors (in decreasing order of importance) affecting recruitment success in the post-fire surveys were species, pre-fire parent density, post-fire age of the vegetation at the time of assessment, and fire season, whereas rainfall (for six months post-fire) and fire return interval (>7 years) had little effect. In the seed-planting experiment, germination occurred during the cooler months and mostly within two months of planting, except for summer-plantings, which took 2–3 months longer to germinate. Although recruitment success differed significantly among planting seasons, sites and species, significant interactions occurred among the experimental factors. In both the post-fire surveys and seed planting experiment, recruitment success in relation to fire- or planting season varied greatly within and among species and sites. Results of these two datasets were furthermore inconsistent, suggesting that proteoid recruitment responses are not related to the season of fire. Germination appeared less rainfall-dependent than in winter-rainfall shrublands, suggesting that summer drought-avoiding dormancy is limited and has less influence on variation in recruitment success among fire seasons. The varied response of proteoid recruitment to fire season (or its simulation) implies that burning does not have to be restricted to particular seasons in eastern coastal fynbos, affording more flexibility for fire management than in shrublands associated with winter rainfall.

scholarly journals Modeled larval fish prey fields and growth rates help predict recruitment success of cod and anchovy in the North Sea

2018 ◽  
Vol 600 ◽  
pp. 111-126 ◽  
Author(s):  
KB Huebert ◽  
J Pätsch ◽  
M Hufnagl ◽  
M Kreus ◽  
MA Peck
Keyword(s):  
North Sea ◽  
Growth Rates ◽  
Larval Fish ◽  
Fish Prey ◽  
Recruitment Success ◽  
The North ◽  
The North Sea
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