Spatial patterns of recruitment in a demersal fish as revealed by seabird diet

Abstract

Understanding recruitment in demersal fish requires determination of larval survival and delivery to appropriate settling habitats. Sanddabs Citharichthys sp. are an abundant neritic fish of Central California, an area of persistent upwelling. 'Upwelling shadows' develop in the lee of coastal promontories, retain surface waters, and may promote spatial variation in fish settlement. To test this hypothesis, we studied the diet and foraging dimensions of a seabird (Cepphus columba) specializing in sanddab consumption at windward and leeward sites over a 6 yr period. We integrated the bird's take of sanddab with information on upwelling intensity and variability and sanddab larval abundance based on net sampling. Seabird diet at both sub-colonies was variable, but dominated by Age 1 sanddabs. Sanddabs were more prevalent in the diet of guillemots at the leeward site, and diet was more variable at the windward site. Persistent upwelling led to regional increases in sanddab larval abundance which, in turn, resulted in enhanced recruitment to leeward waters, as reflected in seabird diet. Pulsed upwelling was related to apparent increased recruitment in windward waters. This study is one of the first to suggest that seabird diet can be used as an indicator of spatial variability in recruitment and settlement of demersal forage fish.

Large interannual variation in spawning in San Diego marine protected areas captured by molecular identification of fish eggs

“…We found a significant negative correlation between annual winter temperatures and annual spring and summer spawning for each year. In contrast, we found no relationship between annual interannual variability in upwelling could alter fish reproductive activity (Robinette et al 2007).…”

“…We also found a significant positive relationship between annual spring upwelling and annual spring-summer fish egg abundance for each year, though additional sampling years are needed to adequately test this relationship. Similar to our study, Robinette et al (2007) found that more persistent annual spring upwelling led to increased larval abundance in central California.…”

“…We found a significant positive relationship between cumulative upwelling index and average fish eggs by month. This is likely driven by seasonal upwelling in the California Current, occurring during the spring and summer that coincides with peak spawning activity (Robinette et al 2007). We also found a significant positive relationship between annual spring upwelling and annual spring-summer fish egg abundance for each year, though additional sampling years are needed to adequately test this relationship.…”

Spatio‐temporal dynamics of ocean conditions and forage taxa reveal regional structuring of seabird–prey relationships

“…We investigated the breeding success of Common Murre ( Uria aalge ), Cassin's Auklet ( Ptychoramphus aleuticus ), Rhinoceros Auklet ( Cerorhinca monocerata ), Pigeon Guillemot ( Cepphus columba ), Brandt's Cormorant ( Phalacrocorax penicillatus ), and Pelagic Cormorant ( Phalacrocorax pelagicus ). All of these seabirds are pursuit‐diving species that select a variety of micronekton, including krill, and forage fish species such as juvenile rockfish, juvenile sanddab, and anchovy as prey for offspring provisioning (Ainley and Boekelheide 1990, Ainley et al 1996 a , b , Sydeman et al 1997, 2001, Robinette et al 2007; see Plate 1). Seabird breeding performance may be related to winter environmental conditions that occurred months before the initiation of breeding (e.g., egg lay date [Ainley and Boekelheide 1990, ]), but breeding success, measured as the number of young raised to fledging age, is largely a function of the parents ability to provision offspring during the chick‐rearing phase (Sydeman et al 2001).…”

Seasonal shift in the foraging niche of Atlantic puffins Fratercula arctica revealed by stable isotope (δ15N and δ13C) analyses

“…Most dietary studies of marine birds are restricted to the breeding season when birds are accessible on land and the prey loads of provisioning adults are observed or intercepted (Robinette et al 2007, Einoder 2009). Such colony-based information likely reflects the diets of chicks and should not necessarily be used to extrapolate adult diet (Williams et al 2007).…”