Age and size structure of Caribbean spiny lobster, Panulirus argus, in a no-take marine reserve in the Florida Keys, USA

Abstract

Fisheries managers worldwide are increasingly using no-take marine reserves (NTMR) to bolster the sustainability of fisheries. Within the Florida Keys National Marine Sanctuary (FKNMS), the Western Sambo Ecological Reserve (WSER) was created to protect a natural area for spawning and a permanent residence area for marine life by eliminating recreational and commercial harvest of resident species. To evaluate whether WSER is meeting these design criteria, we assessed the age structure and potential egg production of the Caribbean spiny lobster (Panulirus argus) population in WSER and in a nearby, unprotected, fished area. Concentration of the age-pigment neurolipofuscin in eyestalks of P. argus was quantified histologically to determine age. We used Monte Carlo simulations to compare the age structure between the two populations of lobster. Lobsters in WSER were older than those in the fished area. Analyses suggested that more than 90% of the lobsters in the fished area were younger than 1.9 years, whereas half of the lobsters in WSER were older than 1.9 years. Moreover, some lobsters may have been the same age (5–6 years) as was WSER itself at the time of the survey, suggesting that they were long-term residents of WSER. Evident in this age-based study was the retention of female lobsters in WSER, as confirmed by the presence of older females, whereas large and thus likely protected females were uncommon during surveys in which only size and sex data were collected. Also, as expected in an older population, the frequency of female lobsters with evidence of maturity was higher in WSER than in the fished areas of the Florida Keys. This research indicates that WSER is functioning as an NTMR, which has resulted in the development of a multiple-year-class lobster population and increased egg production of female lobsters.