Top-down modeling and bottom-up dynamics: Linking a fisheries-based ecosystem model with climate hypotheses in the Northern California Current

To better understand the role played by cetaceans as top-level predators in the California Current ecosystem, we estimate the fraction of annual net primary production (NPP) required to support the prey consumed by cetaceans, using a simple trophic transfer model. The biomass of cetacean species in the California Current is calculated as the product of their mean summer and fall abundance during 1991 to 2005 and estimates of mean mass ind. . Total prey consumption by cetaceans is estimated from a mass-specific consumption model. NPP is estimated from remote satellite measurements using the Behrenfeld-Falkowski vertically-generalized production model for each of 4 geographic regions. The total biomass of baleen whales exceeds the biomass of toothed whales by a factor of ~2.5; however, the estimated prey consumption by these taxa is nearly equal. Assuming 10% trophic transfer efficiency, cetaceans are estimated to require 32.2 g C m -2 yr -1 of primary production, or ~12% of the NPP in the study area, to sustain the prey that they directly consume. Because they feed at a lower trophic level, the primary production requirement (PPR) of baleen whales is 13% of that of toothed whales, despite their 2.5-fold greater biomass. Uncertainty in trophic transfer efficiency results in the greatest uncertainty in estimating PPR for these upper trophic predators.

Section: Taxonmentioning

confidence: 99%

Cetacean biomass, prey consumption, and primary production requirements in the California Current ecosystem

Barlow

Kahru²,

Mitchell³

2008

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…Myctophids represent an important trophic link between phytophagous zooplankton such as copepods and euphausiids and higher trophic level organisms such as salmon, tuna, seabirds, and marine mammals (see review in Brodeur & Yamamura 2005). They dominate the fish biomass in oceanic waters of the Northeast Pacific (Pearcy 1977, Gjøsaeter & Kawaguchi 1980, Beamish et al 1999, and their transport onto continental shelves represents an important flux of energy into these systems, as represented in food web models of the California Current (Field et al 2006).Three lanternfish species (Tarletonbeania crenularis, Stenobrachius leucopsarus, and Diaphus theta) form the bulk of micronekton fishes found in the NCC. These 3 species were reported to account for twothirds of all fishes collected in Isaac-Kidd midwater trawl tows in the upper 200 m off Oregon, USA (Pearcy 1964(Pearcy , 1977.…”

mentioning

confidence: 99%

Trophic ecology of three dominant myctophid species in the northern California Current region

Suntsov

Brodeur²

2008

The feeding ecology of 3 dominant sympatric myctophid species (Tarletonbeania crenularis, Diaphus theta, and Stenobrachius leucopsarus) in the northern California Current System was investigated based on samples collected in June, August, and September of 2006. All 3 species fed predominantly on Euphausia pacifica, the most abundant euphausiid off the central Oregon coast. In contrast, the same 3 lanternfishes showed marked variation in utilization of other principal food categories, and stronger resource partitioning was evident in smaller individuals. The proportion of euphausiids in the diet of T. crenularis and S. leucopsarus gradually increased with increasing size. D. theta at intermediate sizes (31 to 60 mm) preyed heavily upon salps and hyperiid amphipods, whereas the largest specimens consumed mostly euphausiids. S. leucopsarus showed little changes in composition of principal food categories between months, while T. crenularis and D. theta consumed more hyperiid amphipods in June, euphausiids in August, and salps in September. No feeding on salps was recorded in S. leucopsarus for the entire study period. All 3 species showed variation in feeding intensity, stomach fullness, state of digestion, and number of prey species and prey items per stomach. A divergence in feeding strategies of these co-occurring lanternfishes appears to reflect their structural morphology and generally conforms to an ecological subdivision of this midwater family into 'active' and 'inactive' species. Active myctophids (T. crenularis and D. theta) consumed significantly larger amounts of protein-rich prey such as euphausiids, hyperiid amphipods, and salps, while inactive S. leucopsarus showed higher preference for slower-moving, lipid-rich Neocalanus copepods. KEY WORDS:Myctophidae · Mesopelagic · Tarletonbeania crenularis · Diaphus theta · Stenobrachius leucopsarus · Feeding ecology · Ecomorphology · California Current Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 373: [81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96] 2008 Yamamura 2005). Myctophids represent an important trophic link between phytophagous zooplankton such as copepods and euphausiids and higher trophic level organisms such as salmon, tuna, seabirds, and marine mammals (see review in Brodeur & Yamamura 2005). They dominate the fish biomass in oceanic waters of the Northeast Pacific (Pearcy 1977, Gjøsaeter & Kawaguchi 1980, Beamish et al. 1999, and their transport onto continental shelves represents an important flux of energy into these systems, as represented in food web models of the California Current (Field et al. 2006).Three lanternfish species (Tarletonbeania crenularis, Stenobrachius leucopsarus, and Diaphus theta) form the bulk of micronekton fishes found in the NCC. These 3 species were reported to account for twothirds of all fishes collected in Isaac-Kidd midwater trawl tows in the upper 200 m off Oregon, USA (Pearcy 1964(Pearcy , 1977. Due to their high biomass and widespre...

“…A recent attempt to model the marine food web of the eastern Bering Sea was accomplished by Trites et al (1999), who noted that their modeling (using in part ECOSIM and ECOPATH) was incapable of satisfactorily incorporating spatial aspects and especially that of foraging by mobile top predators. Similarly, food web models for the northern California Current (NCC; Field et al 2006, Ruzicka et al 2007), which incorporate biomass and trophic interactions of higher trophic levels, also appear to be poorly resolved in the spatial domain. Most recently, the spatially explicit modeling of Brand et al (2007) has made significant progress in this regard.…”

Section: Introductionmentioning

confidence: 99%

Association of predators and prey at frontal features in the California Current: competition, facilitation, and co-occurrence

Ainley¹,

Dugger²,

Ford³

et al. 2009

We investigated variations in the small-to meso-scale abundance and distribution of the 6 most abundant seabird species in the northern California Current -black-footed albatross Phoebastria nigripes, sooty shearwater Puffinus griseus, pink-footed shearwater Puffinus creatopus, forktailed storm-petrel Oceanodroma furcata, common murre Uria aalge, and Cassin's auklet Ptychoramphus aleuticus -during the upwelling season of 2000 and 2002. Covariates (21 total), with importance assessed using logistic and generalized linear modeling and an information theoretic approach, included physical features such as sea surface temperature, dynamic height (apparent water-column pressure), and pycnocline depth; biological factors such as chlorophyll maximum; and food-web factors such as the density of 3 size classes of zooplankton, the density of potential piscine competitors, i.e. Pacific salmon Oncorhynchus spp., and abundance of fish prey such as zooplankton, northern anchovy Engraulis mordax, and the juveniles of salmon and demersal fishes. The most important factors explaining seabird occurrence changed from mesoscale physical features during a food-rich year (2002; exhibited over 15 to 30 km) to smaller-scale occurrence of actual prey patches during a food-poor year (2000; <1 km). Spatial overlap in occurrence of murres and shearwaters with adult salmon was interpreted as co-occurrence and, perhaps, competition for prey species; a negative spatial overlap between shearwaters and abundance of forage fish was interpreted as evidence for prey depletion (or predator-induced alteration of availability) by the birds and other co-occurring predators (salmon). Overall, results and other information indicated the value of adding spatially explicit data on predator and prey species abundance and predator-prey behavior to improve foodweb modeling.