Spatial comparison of bay morphometrics and age structure in three Oregon estuaries

Cinamon Moffett, Anthony D’Andrea, and Justin Ainsworth Age-Length Keys Introduction Oregon Department of Fish and Wildlife, Marine Resources Program, Newport, OR • Age-length keys were created using the Historical Creel data. Management of Oregon’s bay clam resources and habitats are the [email protected] • Keys were then applied to the Recent Creel and SEACOR data. responsibility of the Oregon Department of Fish and Wildlife (ODFW) Data Set Years Sampled Data Type Methods Parameters • The differences in mean age between data sets were evaluated using Shellfish Program. Bay , which are referred to and managed Data Sets Historical Creel 1983-1991 fisheries dependent recreational length, age from a KS-test (α=0.05). Each estuary with a blue arrow has collectively, include: butter clams (Saxidomus gigantea), cockles harvester growth checks This analysis utilized four interviews significant differences in their estimated age from the known age (Clinocardium nuttallii), gaper clams ( capax), and native existing data sets, each with Recent Creel 2008-2014 fisheries dependent recreational length Do bay clam structure. littleneck clams (Leukoma staminea). This analysis examined bay clam unique characteristics. harvester morphometrics or Most estimated age morphometrics and age structures in three recreationally important interviews age structures Example Age- structures are Oregon estuaries: Netarts, Tillamook and Yaquina bays. Presented here SEACOR-full Netarts-2013-2014 fisheries independent stratified random length, weight, vary on a spatial Length Key significantly different (subtidal and intertidal) Tillamook-2010-2012 sampling width, density between estuaries and are the results from gapers and cockles, which differ in several key life Yaquina-2012 scale? between data sets history traits. Age-size relationships are an informative component of SEACOR-intertidal Netarts-2013-2014 fisheries independent stratified random length, weight, Width measurement bay clam management. These findings will guide future ageing studies. Length measurement estimated age Tillamook-2010-2011 sampling width, density Estimated ages from growth checks Yaquina-2012 Estimated ages Known ages Recent Creel Historical Creel SEACOR-intertidal

Estuaries Netarts Tillamook Length Shell length plots were created for each estuary by data set with mean length shown in red.

Tillamook Bay is the second largest Tillamook outer coast estuary in Oregon and is Cockles Gapers fed by five major rivers. It supports HistoricalCreel Recent Creel SEACOR-intertidal HistoricalCreel Recent Creel SEACOR-intertidal Netarts

Tillamook Bay more than 70% of the state’s Yaquina Netarts Bay commercial bay clam fishery and has Cockles Tillamook one of the most popular recreational 0 2 4 6 8 10 12 0 2 4 6 8 10 12 0 2 4 6 8 10 12 clamming areas in Oregon. Age Age Age

Yaquina Bay Yaquina Netarts Netarts Netarts Bay is a popular location for recreational clamming. Commercial Tillamook harvest of cockles and farming Morphometric Relationships also occur within the bay. Unlike Length/Width Length/Weight Length/Width Length/Weight Gapers most of Oregon’s estuaries, Netarts • SEACOR-full data were used to Yaquina Bay is not fed by a major river. create regression relationships.

0 5 10 15 0 5 10 15 Instead, a number of small streams • The variation in slope between the Age 0 5 Age 10 15 Age a b a b Netarts 1.55E-04 3.07 flow into it from the surrounding Netarts 3.57E-04 3.016 estuaries were evaluated using Tillamook 0.001 2.596 Tillamook 3.31E-04 3.034 Yaquina 7.26E-04 2.748 Yaquina 1.63E-04 3.211 slope watershed. This results in relatively slope ANCOVA (α=0.05). Netarts 0.531 Netarts 0.628 Tillamook 0.545 Tillamook 0.658 high salinity in the bay, enhancing Yaquina 0.566 Findings Morphometrics differ significantly Yaquina 0.723 the quality of shellfish habitat. • Spatial Variability: Cockle and gaper morphometrics and age between estuaries Yaquina structure vary on a spatial scale. Similar results were found for butter The lower Yaquina Bay estuary is a drowned river and native littleneck clams. mouth system with salt marshes, sloughs, and • Data Type: The use of fisheries-dependent data with inherent biases several large mud flats. The bay supports a mosaic Growth Models von Bertalanffy Model Bootstrapped Parameter Estimates of non random sampling and size selectivity may alter predicted of commercial and recreational uses including • The von Bertalanffy model Growth Rate K Hypothetical Max Length L∞ relationships when applied to fisheries-independent data. many popular recreational clamming areas.

(1-e(-K(t-t0)) parameters ( l∞, K, and t0 ) were Lt=Linf ) • Ageing: Reliability of growth checks for ageing varies by species. estimated for each estuary from Bay Clams • Further studies: Spatial variability, data type and ageing method the Historical Creel data. Cockle Coefficients should be taken into consideration both in further data collection K L∞ Netarts 0.30655 89.61943 Cockles Gapers • Differences in model predictions Tillamook 0.282642 80.65045 efforts and in the building and application of growth models Yaquina 0.243091 82.69722 Tillamook n=2245 Netarts n=2065 Clinocardium nuttallii Tresus capax between estuaries were explored Yaquina n=3909 informing the effective scale for fisheries management. 0.1 0.2 0.3 0.4 70 80 L 90 100 by bootstrapping parameter K ∞ • Lengths up to 18 cm mean standard deviation mean standard deviation • Lengths up to 10 cm Netarts 0.3066324 0.0209382 Netarts 89.71225 1.433194 estimates 1000 times and using Tillamook 0.2724552 0.02018469 Tillamook 81.38599 1.55114 Yaquina 82.78443 2.173475 • Found near surface in the mid • Found up to meter deep in the ANOVA with pairwise Yaquina 0.2438718 0.02053463 to low intertidal lower intertidal Acknowledgments comparison using t tests with (1-e(-K(t-t0)) Lt=Linf ) • Life span 15-19 years • Life span 15 years pooled standard deviation • The Shellfish Project is supported by recreational shellfish license fees. • Thanks to all the ODFW staff that collected and processed these data. • Summer reproduction around • Winter reproduction around age (α=0.05). Gaper Coefficients K L∞ Netarts 0.71161 109.2359 year 2 3 or 4 Growth models differ Tillamook 0.190655 131.0633 • Special thanks to Katelyn Bosley for help with R code. Yaquina 0.496122 114.1687 Tillamook n=313 Netarts n=1002 Yaquina n=2327 • Sessile: adult gaper are unable to significantly between 100 110 120 130 140 150 • Mobile: move with a highly 0.0 0.5 K 1.0 1.5 L ∞ mean standard deviation mean standard deviation developed foot rebury once disturbed estuaries Netarts 0.812828 0.19849337 Netarts 109.268 2.0770825 Tillamook 0.191506 0.0301833 Tillamook 131.775 5.4172999 Yaquina 0.4969281 0.01877532 Yaquina 114.1959 0.4802181