Oregon’s estuaries were once disregarded as important habitat for rockfishes (Sebastes spp.), but recent studies have found that some species utilize seagrass and artificial habitats during their early life history, with some idividuals spending at least their first winter of life in the estuary. As the diversity of species observed in Oregon estuaries has increased in recent years, it is possible that estuarine habitats are becoming more important to population sustainability. Examining how juvenile rockfishes use estuarine habitats will therefore provide vital information in understanding the nursery function of PNW estuaries to important commercial and recreational marine species.
This work will first examine various life history traits such as age, growth, settlement date, and feeding ecology of juvenile rockfishes in three Oregon estuaries, Alsea, Nehalem, and Yaquina. These metrics will be used to evaluate habitat quality for each estuary. Mortality is thought to decrease with faster growth rates and a higher quality diet, so it is important to understand if growth rates or diets vary between estuaries. Habitats containing greater abundances of fast growing juveniles before winter may be a better nursery area than habitats where juveniles have reduced growth rates.
It has been argued that density and abundance measurements alone are not sufficient to determine importance of a habitat in regards to subsequent recruitment to adult populations. If recruits in these habitats fail to thrive and never reach adulthood, such an event would be an ecological dead end (i.e. a sink) despite high initial abundances; therefore, juvenile rockfish contribution to the adult population needs to be evaluated for Oregon’s estuaries to further determine the importance of these sensitive habitats for rockfishes.
Otolith microchemical analysis of trace elements is widely used to evaluate the nursery function of estuaries due to differences between estuarine water chemistries. This work will determine whether otolith microchemistry can be useful tool to aid in the understanding and determination of estuaries as juvenile rockfish nursery habitats. If distinct and temporally stable signatures are found among estuaries, this method would be useful to future studies to answer the question of which estuaries contribute more recruits to adult populations.
Brittany D. Schwartzkopf, Department of Fisheries and Wildlife, Oregon State University
Scott A. Heppell, Department of Fisheries and Wildlife, Oregon State University
Hatfield Marine Science Center William and Francis McNeil Fellowship
NOAA’s Living Marine Resource Cooperative Science Center
Hatfield Marine Science Center Mamie Markham Research Fellowship