The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library Summer 8-1-2019 Comparing Independent Approaches to Estimate Age at Size of the Jonah Crab (Cancer borealis): Corroborating Gastric Mill Band Counts as a Direct Aging Method Carlton Huntsberger University of Maine, [email protected] Follow this and additional works at: https://digitalcommons.library.umaine.edu/etd Part of the Marine Biology Commons Recommended Citation Huntsberger, Carlton, "Comparing Independent Approaches to Estimate Age at Size of the Jonah Crab (Cancer borealis): Corroborating Gastric Mill Band Counts as a Direct Aging Method" (2019). Electronic Theses and Dissertations. 3057. https://digitalcommons.library.umaine.edu/etd/3057 This Open-Access Thesis is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. For more information, please contact [email protected]. COMPARING INDEPENDENT APPROACHES TO ESTIMATE AGE AT SIZE OF THE JONAH CRAB (CANCER BOREALIS): CORROBORATING GASTRIC MILL BAND COUNTS AS A DIRECT AGING METHOD By Carlton Huntsberger B.S. Roger Williams University, 2012 A THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science (in Marine Biology) The Graduate School The University of Maine August 2019 Advisory Committee: Richard Wahle, Research Professor, School of Marine Science, Advisor Yong Chen, Professor, School of Marine Science Raouf Kilada, Chief Research Officer, OceAge Copyright 2019 Carlton Huntsberger All Rights Reserved ii COMPARING INDEPENDENT APPROACHES TO ESTIMATE AGE AT SIZE OF THE JONAH CRAB (CANCER BOREALIS): CORROBORATING GASTRIC MILL BAND COUNTS AS A DIRECT AGING METHOD By Carlton Huntsberger Thesis Advisor Dr. Richard Wahle An Abstract of the Thesis Presented In Partial Fulfillment of the Requirements for the Degree of Master of Science (in Marine Biology) August 2019 Knowing the age of an organism is essential in understanding the dynamics and management of wild populations. Age determination has been an especially long-standing challenge in the study of crustaceans, since they posed a unique challenge, shedding all calcified structures with each molt. The Jonah crab (Cancer borealis), is one of many commercially harvested crustaceans for which no absolute aging method has yet been established. It is an ecologically important species and a newly managed fishery in New England and Atlantic Canada. The recent increase of commercial fisheries for this species has highlighted the large data gap of growth and aging information, resulting in high uncertainty of understanding their population dynamics. Direct aging methods for marine species typically rely on counting growth bands preserved in calcified structures. Recent evidence suggests that bands present in the gastric mill of the foregut of lobsters, crabs, and crayfish may accumulate with age. This study compares three independent aging methods to estimate the age-size relationship for Jonah crab through: (1) length frequency analysis of crabs sampled periodically in wild nursery populations including young-of-year crabs, (2) building a probabilistic growth model informed with data from a laboratory growth study, (3) and finally applying the method of direct gastric mill band counts from crabs collected in two contrasting temperature regimes along Maine’s coast. This is the first comprehensive study on the growth of juvenile Jonah crab and providing additional data on mature crabs, enabling absolute age estimates to be determined for the Jonah crab for the first time. Passive settlement collectors and monthly size frequency analysis of juvenile crabs clearly documented the transition from postlarval stages into their benthic phase occurring between July and September. Definitions of these juvenile size classes provided from this study, allows annual size frequency data to be applied as an index of Jonah crab recruitment. The growth study and subsequent molt model have highlighted the variability in growth and will enable management to determine age at legal size for males and information about age at maturity. This study also provides additional supporting evidence that the bands observed in the gastric mill ossicles of crustaceans can be used as direct age indicators. First, I used known age Jonah crabs up to two years old to validate this method. Second, the gastric mill band count method has been corroborated using two indirect aging methods providing a direct one-to-one relationship with age. The regional comparison of band count conducted here demonstrates that the number of bands are not solely dependent upon the size of the animals but are likely age indicators. The results from this study provide fisheries management and scientists a tool to improve their understanding of growth, longevity, and age at specific life history events enabling a better understanding of the biology of the Jonah crab. ACKNOWLEDGMENTS This project would not have been possible without the outstanding support of the Wahle lab, Darling Marine Center, my advisors, and funding from the Maine DMR Research, Education and Development Fund, Maine Sea Grant, and the UMaine School of Marine Science graduate research fellowship. There were many great colleagues assisting with this project, in particular, a special thank you to Bill Favitta for working through all conditions assisting me with data collection, and always making the work more enjoyable. Hattie Train, Hallie Arno, Allison Morin, Rachel Klose, David Gauld, Abby Shaughnessy, Kristyn Holmes, and Alex Asher all also provided invaluable assistance in the field and laboratory. Thank you to my lab mate Maura Niemisto for guidance and support along the way. Thank you to Curt Brown, and Katherine Thompson as well as the ventless trap survey staff for providing me with additional samples. This work would not have been completed without the support of my Advisor, Rick Wahle, who gave me the opportunity for this project and provided guidance along the way while squeezing in meetings on the ski lift. A huge thank you to my committee members first, Raouf Kilada, who worked tirelessly to train me on the method gastric mill analysis as we worked though the challenge of discovering that the entire structure used for this method was lost at molt making it difficult to understand how these bands could be annual. My third committee member, Yong Chen helped me understand the math and coding behind the fisheries models developing my skills to produce this final project. Thank you again to my entire committee. Finally, I would like to thank my friends, classmates, family and of course my dog, Zoey for the lunch breaks, hikes, pizza nights, and endless support along the way. iii TABLE OF CONTENTS ACKNOWLEDGMENTS ................................................................................................. iii LIST OF TABLES ............................................................................................................. iv LIST OF FIGURES ......................................................................................................... vii LIST OF ABBREVIATIONS ......................................................................................... viii CHAPTERS 1. JONAH CRAB GROWTH AND AGING; SIZE FREQUENCY ANALYSIS 1.1. Introduction .......................................................................................................1 1.2. Methods ..........................................................................................................6 1.2.1. Monthly larval settlement and post-settlement growth observations ..........................................................................6 1.2.2. Evaluation of annual survey data for size frequency analysis ...........8 1.2.3 Size frequency analysis of existing annual survey data: WGoM...................................................................................10 1.2.4 Size frequency analysis of existing annual survey data: EGoM ....................................................................................10 1.3. Results ........................................................................................................11 1.3.1. Monthly larval settlement and post-settlement growth observations ........................................................................11 1.3.2. Size frequency analysis of existing annual survey data WGoM ....................................................................................13 1.3.3. Size frequency analysis of existing annual survey data EGoM .....................................................................................16 iv 1.4. Discussion .......................................................................................................18 1.5. Conclusions .....................................................................................................20 2. JONAH CRAB GROWTH AND AGING; PROBABILISTIC MOLT MODEL 2.1. Introduction .....................................................................................................21 2.2. Methods ........................................................................................................24 2.2.1. Laboratory Growth Study ................................................................24 2.2.2 Probabilistic Growth Model ..............................................................25 2.3.