STATE OF WASHINGTON December 2005 Length-Weight Models for Intertidal Clams in Puget Sound (Bivalve Regions 1, 5, 6, 7, and 8) by Alex Bradbury, Brady Blake, Camille Speck, and Doug Rogers WashingtonWashington DepartmentDepartment ofof FISHFISH ANDAND WILDLIFEWILDLIFE FishFish ProgramProgram FishFish ManagementManagement DivisionDivision FPT 05-15 Length-Weight Models for Intertidal Clams in Puget Sound (Bivalve Regions 1, 5, 6, 7, and 8) by Alex Bradbury, Brady Blake, Camille Speck and Doug Rogers December 2005 Table of Contents Table of Contents............................................................................................................................. i List of Tables .................................................................................................................................. ii List of Figures................................................................................................................................. v Acknowledgements....................................................................................................................... vii Introduction..................................................................................................................................... 1 Methods........................................................................................................................................... 4 Sampling Sites and Field Methods ............................................................................................. 4 Laboratory Measurements .......................................................................................................... 5 Analytical Methods..................................................................................................................... 5 Empirical Model Comparisons ............................................................................................... 7 Change in Length-Weight Relationships over Time .............................................................. 8 Results............................................................................................................................................. 9 Length-Weight Models ............................................................................................................... 9 Manila Clams.......................................................................................................................... 9 Native Littleneck Clams ....................................................................................................... 15 Butter Clams ......................................................................................................................... 21 Cockles.................................................................................................................................. 27 Eastern softshell clams.......................................................................................................... 33 Empirical Model Comparisons ................................................................................................. 38 Manila Clams........................................................................................................................ 38 Native littleneck clams.......................................................................................................... 40 Change in Length-Weight Relationships over Time ............................................................ 42 Summary and Recommendations ................................................................................................. 45 References Cited ........................................................................................................................... 48 Appendix 1: A comparison of fresh and frozen weights of Manila clams sampled in a clam population survey.......................................................................................................................... 49 Introduction............................................................................................................................... 50 methods..................................................................................................................................... 51 Results....................................................................................................................................... 52 Discussion................................................................................................................................. 52 References Cited ....................................................................................................................... 55 Length-Weight Models for Intertidal Clams in Puget Sound December 2005 i List of Tables Table 1. Public beaches providing samples for length-weight models of Manila clams. Bold type indicates that sample size n ≥ 100 clams, allowing for estimation of beach- specific model parameters........................................................................................... 10 Table 2. Parameter estimates of beach-specific length-weight models for Manila clams. Only beaches shown in Table 1 with n ≥ 100 clams were used to estimate beach-specific parameters................................................................................................................... 11 Table 3. Parameter estimates of regional length-weight models for Manila clams. Beaches sampled in each Bivalve Region are listed in Table 1................................................ 11 Table 4. Public beaches providing samples for length-weight models of native littleneck clams. Bold type indicates that sample size n ≥ 100 clams, allowing for estimation of beach-specific model parameters................................................................................ 16 Table 5. Parameter estimates of beach-specific length-weight models for native littleneck clams. Only beaches shown in Table 4 with n ≥ 100 clams were used to estimate beach-specific parameters........................................................................................... 17 Table 6. Parameter estimates of regional length-weight models for native littleneck clams. Beaches sampled in each Bivalve Region are listed in Table 4.................................. 17 Table 7. Public beaches providing samples for length-weight models of butter clams. Bold type indicates that sample size n ≥ 200 clams, allowing for estimation of beach- specific models............................................................................................................ 22 Table 8. Parameter estimates of beach-specific length-weight models for butter clams. Only beaches shown in Table 7 with n ≥ 200 clams were used to estimate beach-specific parameters................................................................................................................... 23 Table 9. Parameter estimates of regional length-weight models for butter clams. Beaches sampled in each Bivalve Region are listed in Table 7................................................ 23 Table 10. Public beaches providing samples for length-weight models of cockles. Bold type indicates that sample size n ≥ 100 clams, allowing for estimation of beach-specific model parameters........................................................................................................ 28 Table 11. Parameter estimates of beach-specific length-weight models for cockles. Only beaches shown in Table 10 with n ≥ 100 clams were used to estimate beach-specific parameters................................................................................................................... 29 Table 12. Parameter estimates of regional length-weight models for cockles. Beaches sampled in each Bivalve Region are listed in Table 10. ........................................................... 29 Length-Weight Models for Intertidal Clams in Puget Sound December 2005 ii Table 13. Public beaches providing samples for length-weight models of eastern softshell clams. Bold type indicates that sample size n ≥ 100 clams, allowing for estimation of beach-specific parameters........................................................................................... 34 Table 14. Parameter estimates of beach-specific length-weight models for eastern softshell clams. Only beaches shown in Table 13 with n ≥ 100 were used to estimate beach- specific parameters...................................................................................................... 34 Table 15. Parameter estimates of regional length-weight models for eastern softshell clams. Beaches sampled in each Bivalve Region are listed in Table 13................................ 35 Table 16. A comparison of the estimated mean weight per legal Manila clam ( ≥ 38 mm) based on actual weighed samples and on length-weight models. Data from WDFW surveys in 2001 and Skokomish Tribe survey of Potlatch East in 2002. “Difference (%)” is the difference between the modeled mean weight and the actual survey mean weight, expressed as a percentage. WDFW models are from this report; Sea Grant model is from Anderson et al. (1982)........................................................................................ 39 Table 17. A comparison of the estimated legal Manila clam ( ≥ 38 mm) biomass based on actual weighed samples and on length-weight models. “Difference (pounds)” is the difference between the modeled biomass and the estimated survey biomass. Estimates