Foraging performance and reproductive success of Humboldt penguins in relation to prey availability

The Eastern Baltic cod abundance started rapidly to increase in the mid-2000s as evidenced by analytical stock assessments, due to increased recruitment and declining fishing mortality. Since 2014, the analytical stock assessment is not available, leaving the present stock status unclear and casting doubts about the magnitude of the recent increase in recruitment. Earlier studies identified main factors impacting on cod reproductive success to be related to the loss of two out of three spawning areas in the 1980s caused by lack of major Baltic inflows with a concurrent reduction in salinity and oxygen. Other important factors include prey availability for first-feeding larvae, egg predation by sprat and herring and cannibalism on juveniles, all in one way or the other related to the prevailing hydrographic conditions. These factors cannot explain increased reproductive success in the last decade, as the period was characterized by an absence of large-scale Baltic inflows since 2003 and persistent anoxic conditions in the bottom water of the deep Baltic basins. This questions the perception of the increased recruitment in later years and challenges our present understanding of cod recruitment dynamics in the Baltic Sea. In this contribution, we review evidence from the recent literature supplemented by information from latest research cruises to elucidate whether cod reproductive success indeed has increased during the last decade, and we suggest the key processes responsible for the recent dynamics in cod recruitment and outline directions for future research.

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Effects of grazing on vegetation structure, prey availability, and reproductive success of Grasshopper Sparrows

Journal of Field Ornithology ◽

10.1648/0273-8570-76.4.345 ◽

2005 ◽

Vol 76 (4) ◽

pp. 345-351 ◽

Cited By ~ 33

Author(s):

Benjamin Sutter ◽

Gary Ritchison

Keyword(s):

Reproductive Success ◽

Vegetation Structure ◽

Prey Availability

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Floral Resources Enhance Fecundity, but Not Flight Activity, in a Specialized Aphid Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.748870 ◽

2021 ◽

Vol 9 ◽

Author(s):

Hannah E. Stowe ◽

J. P. Michaud ◽

Tania N. Kim

Keyword(s):

Body Size ◽

Reproductive Success ◽

Prey Availability ◽

Flight Activity ◽

Flight Behavior ◽

Floral Resources ◽

Adult Survival ◽

Adult Size ◽

Hippodamia Convergens ◽

Adult Diet

Adult aphid predators disperse across the landscape seasonally in search of prey aggregations that are patchily distributed and temporally variable. However, flight is energetically costly and consumes resources that could be invested in reproduction. Hippodamia convergens is an important aphid predator in North American cereal crops and other agricultural systems. Consumption of floral resources can enhance adult survival during periods of low prey availability and may improve reproductive success. We tested how an omnivorous adult diet containing floral resources (diluted honey and pulverized bee pollen) interacts with body size to influence reproduction and flight behavior compared to a prey-only diet. Two sizes of beetles were produced by controlling larval access to food—3 h daily access produced small beetles; ad libitum access produced large beetles with faster development. Reproductive performance was tracked for 18 days, and female flight activity was assayed via 3 h bouts of tethered flight. Diet composition and body size interacted to influence preoviposition period, with large females in prey-only treatments delaying oviposition the longest. The omnivorous adult diet improved 18-day fecundity relative to a prey-only diet, but egg fertility was unaffected. Adult size affected oviposition pattern, with small beetles laying smaller, but more numerous, clutches. Females flew up to 7 km in 6 h, but neither body size nor adult diet influenced flight distance, suggesting that all diet treatments generated energy reserves sufficient to power flights of short duration. However, pre-reproductive females flew > 60% further than they did post-reproduction, likely due to the energetic costs of oviposition. Thus, access to pollen and nectar increased reproductive success and altered oviposition patterns in H. convergens, indicating the importance of floral resources in the agricultural landscape to conservation of this predator and its biological control services.

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