State Of The California Current 2016-17: Still Anything But "Normal" In The North

Citation:
Wells, BK, Schroeder ID, Bograd SJ, Hazen EL, Jacox MG, Leising A, Mantua N, Santora JA, Fisher J, Peterson WT, Bjorkstedt E, Robertson RR, Chavez FP, Goericke R, Kudela R, Anderson C, Lavaniegos BE, Gomez-Valdes J, Brodeur RD, Daly EA, Morgan CA, Auth TD, Field JC, Sakuma K, McClatchie S, Thompson AR, Weber ED, Watson W, Suryan RM, Parrish J, Dolliver J, Loredo S, Porquez JM, Zamon JE, Schneider SR, Golightly RT, Warzybok P, Bradley R, Jahncke J, Sydeman W, Melin SR, Hildebrand JA, Debich AJ, Thayre B.  2017.  State Of The California Current 2016-17: Still Anything But "Normal" In The North. California Cooperative Oceanic Fisheries Investigations Reports. 58:1-55.

Date Published:

2017/12

Keywords:

baja-california, chinook salmon, current system, ecosystem, el-nino, marine, modeling-system, ocean conditions, oceanographic conditions, plume, river, sea lions

Abstract:

This report examines the ecosystem state of the California Current System (CCS) from spring 2016-spring 2017. Basin-scale indices suggest conditions that would support average to below average coast-wide production across the CCS during this time period. Regional surveys in 2016 sampled anomalously warm surface and subsurface waters across the CCS. Chlorophyll concentrations were low across the CCS in 2016 and, concomitant with that, copepod communities had an anomalously high abundance of subtropical species. Early in 2017 conditions between northern, central, and southern CCS were dissimilar. Specifically, surface conditions north of Cape Mendocino remained anomalously warm, chlorophyll was very low, and subtropical copepods were anomalously abundant. Southern and central CCS surveys indicated that environmental conditions and chlorophyll were within normal ranges for the longer time series, supporting an argument that biophysical conditions/ecosystem states in the southern and central CCS were close to normal. Epipelagic micronekton assemblages south of Cape Mendocino were generally close to longer-term average values, however the northern assemblages have not returned to a "normal" state following the 2014-15 large marine heatwave and 2016 El Nino. North of Cape Mendocino the epipelagic micronekton was largely composed of offshore and southern derived taxa. We hypothesize that stronger-than-typical winter downwelling in 2017 and a reduced spawning biomass of forage taxa are contributors to the anomalous forage community observed in the north. Also of note, surveys indicate northern anchovy (Engraulis mordax) abundance was greater than average (for recent years) and nearer shore in northern regions. Finally, record-low juvenile coho and Chinook salmon catches in the 2017 northern CCS salmon survey suggest that out-migrating Columbia Basin salmon likely experienced unusually high early mortality at sea, and this is further supported by similarities between the 2017 forage assemblage and that observed during poor outmigration survival years in 2004, 2005, and 2015. Generally, the reproductive success of seabirds in 2016 (the most current year available) was low in the north but near average in central California. At Yaquina Head off Oregon and Castle Rock off northern California some of the lowest reproductive success rates on record were documented. In addition to reduced abundance of prey, there was a northward shift of preferred seabird prey. Seabird diets in northern areas also corroborated observations of a northward shift in fish communities. Nest failure was attributed to a combination of bottom-up and top-down forces. At Castle Rock, most chicks died of starvation whereas, at Yaquina Head, most nests failed (95% of common murre, Uria aagle) due to disturbance by bald eagles (Haliaeetus leucocephalus) seeking alternative prey. Mean bird densities at sea for the 2017 surveys between Cape Flattery Washington and Newport Oregon were the lowest observed and may indicate continued poor reproductive performance of resident breeders in 2017. South of Cape Mendocino, where forage availability was typical, seabird reproductive success was also below average for most species in 2016, but did not approach failure rates observed in the north. Finally, in 2017, abundances of seabirds observed at-sea off southern California were anomalously high suggesting an improved foraging environment in that area. Marine mammal condition and foraging behavior were also impacted by the increased abundance and shifting distribution of the northern anchovy population. Increases in the abundance of northern anchovy in the Southern California Bight coincided with improved condition of sea lion (Zalophus californianus) pups in 2016. Namely, lipid-rich northern anchovy occurred in great frequencies in the nursing female diet. Increases in northern anchovy nearshore in the central and northern CCS may have also contributed to a shoreward shift in distribution of humpback whales (Megaptera -novaeangliae) in these regions. These shifts along with recovering humpback whale populations contributed to recent increases in human-whale interactions (e.g., fixed-gear entanglements).

Notes:

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