Population dynamics and production of Phyllorhiza punctata (Cnidaria: Scyphozoa) in Laguna Joyuda, Puerto Rico

Abstract

Medusae of Phyllorhiza punctata were sampled in Laguna Joyuda from October 1985 through October 1986. Maximum numerical abundance (143 ind. per 103 m3) and population biomass (530.6 mg ash-free dry wt [AFDW] m-3) were observed during summer Net increments In population biomass were associated with growth of individuals from October to December and with individual growth and subsequent recruitment of small medusae from May to August. More than 75 '', of the total recruitment into the smallest size classes (< 3 cm) occurred in June, indicative of one large cohort from which most of the summer population developed. High mortality was observed after December 1985, and between August and October 1986. Recruitment of the smaller medusae by early summer and mortality of large adults (> 30 cm) during late summer in the following year suggests that P. punctata follows an annual cycle in Laguna Joyuda. Growth rates, calculated from increases In mean individual weight of held-collected specimens, were exponential during autumn (mean g,. = 0.077 d -l ) , and fl-om June through August (summer; mean gw = 0.079 d-l). Individual growth rates declined with increasing size durlng both these growth stanzas, but faster growth rates were observed In autumn for medusae of equivalent or larger size. Total population biomass increased exponentially at rates of ca 0 063 and 0.028 d-l during October to December 1985 and May to August 1986 respectively. The slower growth rates in summer coincided with a marked reduction in abundance of non-gelatinous zooplankton, suggesting that medusae could have been food limited at this time. Nevertheless, estimated population production rates were much higher during summer (maximum 14.3 mg AFDW m-3 d.') due to the higher population biomass compared to autumn (maximum 1.6 mg AFDW m-%-').

Geographic separation of stocks of the edible jellyfish Catostylus mosaicus (Rhizostomeae) in New South Wales, Australia

“…Similar seasonal patterns of abundance of A. aunta were also observed from 4 yr of sampling in the Gullmar Fjord, Sweden (Grondahl 1988). Garcia (1990), in a study in Puerto Rico, also suggested that the rhizostome PhyIIorhiza punctata displayed seasonality, with medusae being most abundant during summer months. Temporal variation in Garcia's study, however, may not be seasonal, as s a m p h g was only done over a period of 12 mo and sampling for periods of greater than 1 yr is required to determine generality of seasonal patterns (as was clearly demonstrated by the present study).…”

“…This contrasts with several other studies which have demonstrated seasonal variation in abundance (e.g. Grondahl 1988, Garcia 1990, Lucas & Williams 1994. In some studies, however, measures of abundance have been crude (Brewer 1989, Rippingale & Kelly 1995.…”

“…The unit stock for the New South Wales jellyfish fishery should, therefore, be considered to be a population within an estuary. This conclusion is probably also relevant to species in other parts of the world, particularly where populations appear to be topographically confined, such as in fjords (Grondahl 1988, Hamner et al 1994) and estuarine lakes with restricted access to the open ocean (Hamner & Hauri 1981, Garcia 1990, Lucas et al 1997. The New South Wales jellyfish fishery is currently managed as a single stock, with 1 quota set for the entire fishery.…”

Using nowcast model currents to explore transport of non-indigenous jellyfish into the Gulf of Mexico

“…oceanic islands, estuaries and other enclosed or semi-enclosed bodies of water), the ability to predict what will invade and when depends on a variety of factors involving recipient and source habitats as well as environmental sto- To understand how Phyllorhiza punctata might overcome the obstacles of long-distance transport and crossshelf exchange, we considered both the life-history of this jellyfish and the physical mechanism of transport and shelf exchange. Like other Scyphozoa, the medusa stage of P. punctata can live for many months (Garcia 1990, Garcia & Durbin 1993, Graham et al 2003a). Starvation during transport on the order of 2 mo is not expected to occur, since eddies can be viewed as 'oases' of planktonic productivity, especially along their fringes (Zimmerman & Biggs 1999, Biggs & Ressler 2001.…”

“…Like other Scyphozoa, the medusa stage of P. punctata can live for many months (Garcia 1990, Garcia & Durbin 1993, Graham et al 2003a. Starvation during transport on the order of 2 mo is not expected to occur, since eddies can be viewed as 'oases' of planktonic productivity, especially along their fringes (Zimmerman & Biggs 1999, Biggs & Ressler 2001.…”