The ocean quahog (Arctica islandica) support an economically important fishery in the US, though little is known about their life history traits. To determine how these traits vary geographically, the age frequencies and growth rates from two New Jersey sites (NJ1 & NJ2) as well as Georges Bank (GB) and Long Island (LI) were analyzed. Though sexual dimorphism in bivalves is rare, recent research has shown that A. islandica display distinct differences in sizes between males and females, with females reaching larger sizes than those of males. To determine when this difference in size occurs, the growth rates of males and females were analyzed using Welch’s t-test. Results indicate that females begin outgrowing males between the ages of 10-15, at an average size of 50-55 mm. Rarely do males keep pace in growth with females beyond this point. Larger sizes in females may influence their presence in age frequencies based on size selectivity (> 80 mm) by commercial dredge. This is observed in the New Jersey sex ratios, as females are more frequent at a ratio 1:~0.80 at both sites. Age frequencies of NJ1 are very similar to those of LI and GB, yet NJ2 displays recruitment events not observed in any of the other sites. When comparing growth rates, A. islandica from southern sites are reaching milestone sizes 2-3x faster than those of Georges Bank, an effect of warmer bottom water temperatures in these southern areas.
","abstract_html":"<p>The ocean quahog (<em>Arctica islandica</em>) support an economically important fishery in the US, though little is known about their life history traits. To determine how these traits vary geographically, the age frequencies and growth rates from two New Jersey sites (NJ1 & NJ2) as well as Georges Bank (GB) and Long Island (LI) were analyzed. Though sexual dimorphism in bivalves is rare, recent research has shown that <em>A. islandica</em> display distinct differences in sizes between males and females, with females reaching larger sizes than those of males. To determine when this difference in size occurs, the growth rates of males and females were analyzed using Welch’s t-test. Results indicate that females begin outgrowing males between the ages of 10-15, at an average size of 50-55 mm. Rarely do males keep pace in growth with females beyond this point. Larger sizes in females may influence their presence in age frequencies based on size selectivity (> 80 mm) by commercial dredge. This is observed in the New Jersey sex ratios, as females are more frequent at a ratio 1:~0.80 at both sites. Age frequencies of NJ1 are very similar to those of LI and GB, yet NJ2 displays recruitment events not observed in any of the other sites. When comparing growth rates, <em>A. islandica</em> from southern sites are reaching milestone sizes 2-3x faster than those of Georges Bank, an effect of warmer bottom water temperatures in these southern areas.</p>","abstract_has_math":false,"creators":["Sower, Jillian"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Masters Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Eric N. Powell","Roger Mann","Chet Rakocinski"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022-12-20T08:00:00Z","date_published":"2022-12-20T08:00:00Z","updated_at":"2026-07-24T05:45:40Z","subjects":[],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aquila.usm.edu/masters_theses/938","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Eric N. Powell","Roger Mann","Chet Rakocinski"]},{"key":"dc:creator","label":"Author","values":["Sower, Jillian"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2022-12-20T08:00:00Z"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Masters Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://aquila.usm.edu/masters_theses/938"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The ocean quahog (Arctica islandica) support an economically important fishery in the US, though little is known about their life history traits. To determine how these traits vary geographically, the age frequencies and growth rates from two New Jersey sites (NJ1 & NJ2) as well as Georges Bank (GB) and Long Island (LI) were analyzed. Though sexual dimorphism in bivalves is rare, recent research has shown that A. islandica display distinct differences in sizes between males and females, with females reaching larger sizes than those of males. To determine when this difference in size occurs, the growth rates of males and females were analyzed using Welch’s t-test. Results indicate that females begin outgrowing males between the ages of 10-15, at an average size of 50-55 mm. Rarely do males keep pace in growth with females beyond this point. Larger sizes in females may influence their presence in age frequencies based on size selectivity (> 80 mm) by commercial dredge. This is observed in the New Jersey sex ratios, as females are more frequent at a ratio 1:~0.80 at both sites. Age frequencies of NJ1 are very similar to those of LI and GB, yet NJ2 displays recruitment events not observed in any of the other sites. When comparing growth rates, A. islandica from southern sites are reaching milestone sizes 2-3x faster than those of Georges Bank, an effect of warmer bottom water temperatures in these southern areas.
"]},{"key":"dc:title","label":"Title","values":["THE INFLUENCE OF SPATIALHETEROGENEITY ON OCEAN QUAHOG (ARCTICA ISLANDICA) POPULATION DYNAMICS ALONG THE MID-ATLANTIC BIGHT"]}]}],"canonical_facts":{"dc:contributor":["Eric N. Powell","Roger Mann","Chet Rakocinski"],"dc:creator":["Sower, Jillian"],"dc:date.available":["2022-12-20T08:00:00Z"],"dc:description.abstract":["The ocean quahog (Arctica islandica) support an economically important fishery in the US, though little is known about their life history traits. To determine how these traits vary geographically, the age frequencies and growth rates from two New Jersey sites (NJ1 & NJ2) as well as Georges Bank (GB) and Long Island (LI) were analyzed. Though sexual dimorphism in bivalves is rare, recent research has shown that A. islandica display distinct differences in sizes between males and females, with females reaching larger sizes than those of males. To determine when this difference in size occurs, the growth rates of males and females were analyzed using Welch’s t-test. Results indicate that females begin outgrowing males between the ages of 10-15, at an average size of 50-55 mm. Rarely do males keep pace in growth with females beyond this point. Larger sizes in females may influence their presence in age frequencies based on size selectivity (> 80 mm) by commercial dredge. This is observed in the New Jersey sex ratios, as females are more frequent at a ratio 1:~0.80 at both sites. Age frequencies of NJ1 are very similar to those of LI and GB, yet NJ2 displays recruitment events not observed in any of the other sites. When comparing growth rates, A. islandica from southern sites are reaching milestone sizes 2-3x faster than those of Georges Bank, an effect of warmer bottom water temperatures in these southern areas.
"],"dc:identifier":["https://aquila.usm.edu/masters_theses/938"],"dc:title":["THE INFLUENCE OF SPATIALHETEROGENEITY ON OCEAN QUAHOG (ARCTICA ISLANDICA) POPULATION DYNAMICS ALONG THE MID-ATLANTIC BIGHT"],"thesis:degree_level":["Masters Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:45:40Z"}