ORIGINAL RESEARCH article

Front. Mar. Sci.

Sec. Marine Molecular Biology and Ecology

Volume 12 - 2025 | doi: 10.3389/fmars.2025.1558793

This article is part of the Research TopicNew Techniques for Providing a Window Into the Opaque OceanView all 6 articles

Oceanographic and trophodynamic underpinnings of anchovy success in the northern California Current

Provisionally accepted
  • 1Department of Integrative Biology, College of Science, Oregon State University, Corvallis, Oregon, United States
  • 2Hatfield Marine Science Center, Oregon State University, Newport, Oregon, United States

The final, formatted version of the article will be published soon.

Globally, anchovy and sardine typically display asynchronous population fluctuations with anchovy dominating during cool periods and sardine dominating during warm periods. However, this anchovy-sardine cold-warm paradigm has recently broken down in the California Current, suggesting that recruitment may not be a simple product of large-scale physical drivers. Instead, consideration of larval fish trophodynamics together with local oceanography is likely necessary to mechanistically relate survival and recruitment to the physical environment. We examined otolith-derived metrics of northern anchovy (Engraulis mordax) growth in the context of local oceanography and anchovy in situ prey and zooplankton predators in the northern California Current (NCC). Anchovy growth was spatially variable and the regions that conferred heighted growth differed with regard to the crossshelf extent of upwelled waters. When upwelling was restricted to the nearshore environment, anchovy larvae grew significantly faster inshore than offshore. Conversely, when the upwelling front moved farther offshore following sustained upwelling, offshore anchovy larvae grew significantly faster than inshore larvae. Modelling individual anchovy growth revealed that growth was affected by ambient copepod prey availability and gelatinous zooplankton predation pressure, with growth peaking at intermediate prey availability and the highest abundance of predators. Fast growth under high predation pressure may be indicative of the selective loss of slow growing larvae. Notably, larval anchovy abundances were high offshore but diminished immediately inshore of the upwelling front regardless of its cross-shelf position. This suggests that the upwelling front may act as a shoreward boundary for anchovy larvae, affecting their access to the highly nutritious prey base typical of the Oregon continental shelf waters in summer. Variation in larval anchovy growth with local oceanographic conditions and fine-scale distributions of prey and predators provides a mechanistic hypothesis of food-web dynamics which will enhance our ability to predict the response of forage fishes to ecosystem variability.

Keywords: Northern anchovy (Engraulis mordax), Trophodynamics, Northern California Current, upwelling, Zooplankton

Received: 20 Jan 2025; Accepted: 22 Apr 2025.

Copyright: © 2025 Swieca, Sponaugle, Schmid, Ivory and Cowen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Kelsey Shea Swieca, Department of Integrative Biology, College of Science, Oregon State University, Corvallis, 97331, Oregon, United States

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