Population dynamics of the nonindigenous brown mussel Perna perna in the Gulf of Mexico compared to other world-wide populations

Abstract

Texas Gulf of Mexico populations of the marine mytilid Perna perna (Linnaeus, 1758) were sampled monthly on Fish Pass Jetty (FP) (27°41¹N) from September 1993 to February 1995 and Mansfield Pass Jetty (MP) (26°34¹N) from March 1994 to June 1995 within 1 yr of initial colonization. Population density and mussel size distributions allowed identification of annual cohorts. Mean individual tissue and shell ash-free dry weights (AFDW) from subsamples allowed estimation of cohort standing crop shell + tissue biomass. FP was dominated by the 1993 cohort, while 1992 and 1993 cohorts dominated MP. At both sites, poorly recruited 1994 cohorts had negligible biomass or production. FP 1993 cohort density declined from 15000 to 1000 m-2 while those of the 1992 and 1993 MP cohorts declined from 1000 to 100 and 2000 to 1000 m-2, over their respective sampling periods. First-year shell growth was 42 and 53 mm at FP and MP, respectively. AFDW biomass and monthly productivity at both sites remained constant through time. Mean annual FP AFDW biomass = 1.95 kg m-2 and production = 2.44 kg m-2 yr-1; respective values for MP were 1.35 kg m-2 and 1.86 kg m-2 yr-1. Spawning periods, marked by reduced mean individual production, extended from March to October at temperatures >18 to 20°C. The MP 1993 cohort did not reproduce. Gamete release accounted for 76 and 74% of total production in the 1993 FP and 1992 MP cohorts, respectively. Laboratory spawned mussels lost 60% of tissue AFDW regardless of sex. Growth rate, biomass, productivity and reproductive effort in Texan populations were similar to those of other P. perna populations, suggesting that North American Gulf of Mexico shores can support this species.