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° 41' N) from September 1993 to February 1995 and Mansfield Pass Jetty (MP) (26° 34' N) from March 1994 to June 1995 within 1 yr of initial colonization. Population density and mussel size distributions allowed identification of annual cohorts. Mean indi- vidual 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 pro- duction. FP 1993 cohort density declined from 15 000 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 pro- ductivity 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, suggest- ing that North American Gulf of Mexico shores can support this species.