title: Age, growth and hatch dates of ingressing larvae and surviving juveniles of Atlantic menhaden Brevoortia tyrannus.
abstract: Ages, growth and hatch dates of ingressing Brevoortia tyrannus larvae were determined in a 3 year sampling survey at the mouth of the Chesapeake Bay, U.S.A. To determine if otolith-aged cohorts had variable relative survival, hatch dates of summer-caught young-of-the-year (YOY) juveniles collected throughout the Chesapeake Bay were compared with hatch dates of ingressing larvae. Modal total length of ingressing larvae was similar among years: 28 mm in 2005-2006 and 2007-2008, and 30 mm in 2006-2007. Ages of ingressing larvae ranged from 9 to 96 days post hatch (dph); mean ages were similar among years, but significantly older in 2006-2007 (50 dph) than in 2005-2006 (44 dph) and 2007-2008 (46 dph). Larval growth rates differed among years. Earliest growth, when larvae were offshore (0-20 dph), was faster in 2006-2007 (0·62 mm day(-1)), than in 2005-2006 and 2007-2008 (0·55 mm day(-1) in these years). Subsequently, from 30 to 80 dph, growth was slowest in 2006-2007. Hatch dates of ingressing larvae occurred from September to March and 90% (2007-2008) to 98% (2006-2007) had hatched prior to 31 December. In contrast, most surviving YOY juvenile B. tyrannus had hatched in January to February, suggesting selective mortality of early-hatched individuals, apparently during the overwinter, larval to juvenile transition period.
authors.affiliation: University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, Solomons, MD 20688, USA. lozano@umces.edu
authors.forename: C
authors.initials: C
authors.lastname: Lozano
authors.forename: E D
authors.initials: ED
authors.lastname: Houde
authors.forename: R L
authors.initials: RL
authors.lastname: Wingate
authors.forename: D H
authors.initials: DH
authors.lastname: Secor
mesh_terms: D017677:Age Distribution; D000818:Animals; D049628:Body Size; D005399:Fishes / Q000254:growth & development / Q000502:physiology*; D010037:Otolithic Membrane / Q000033:anatomy & histology; D012621:Seasons; D016019:Survival Analysis