Determining the Importance of Food Quality and Temperature on the Growth and Condition of Juvenile Southern Tanner crab (Chionoecetes bairdi) Using Complimentary Field and Laboratory Based Approaches.
Louise Copeman1,2, Clifford Ryer3, Mara L. Spencer3, Michele Ottmar3 and Angie L. Sremba2, (1)Oregon State University, College of Earth, Ocean and Atmospheric Sciences, Oregon, United States, (2)Oregon State University, Cooperative Institute for Marine Resources Studies, Newport, OR, United States, (3)National Oceanic and Atmospheric Administration, Alaska Fisheries Science Center, Fisheries Behavioral Ecology Program, Newport, OR, United States
Abstract:
Shallow nearshore embayments represent important nursery habitats for juvenile southern Tanner crab (Chionoecetes bairdi) as they provided refuge from predation and elevated water temperatures that stimulate growth. Rapid growth during the early juvenile stages is vital as it reduces the risk of predation during early stages. Considerable variability has been observed between growth rates of crabs from different nursery habitats surrounding Kodiak, Alaska. In order to determine the proportion of this variability that is due to diet quality, we sampled sediments and multiple molt stages of juvenile crabs over two years in nursery sites with disparate growth rates. Juvenile crabs reside at the sediment-water interface and therefore, we analyzed sedimentary grain size, sedimentary organic matter as well as total lipids per weight, lipid classes and fatty acid biomarkers in both crabs and sediments. Juvenile crabs from sheltered sites that had finer sediments with high sedimentary lipids demonstrated elevated growth rates and higher storage lipids. Further, storage lipid in crabs from sheltered bays was characterized by higher proportions of diatom and bacterial fatty acid markers. Controlled laboratory experiments were run to determine the relative importance of temperature (2 to 9 °C), food quantity (ration) and food quality (% lipid) on juvenile growth and condition. We found temperature had the most significant impact on crab growth but both quantity and dietary quality also significantly impacted growth and lipid storage. Our result help define characteristics of essential nursery habitat for commercially important cold-water crab species.
