| Marine reserves are gaining favor as an ecosystem-based approach for protecting exploited fisheries. One anticipated reserve benefit is that the protection they afford broodstock will result in increased ichthyoplankton production, a condition difficult to demonstrate in most coastal settings. The estuarine fisheries reserve at Kennedy Space Center (KSC), Florida, is hydrologically isolated from public areas by shorelines and manmade causeways. This characteristic, coupled with the microtidal setting of the northern Indian River Lagoon (IRL) system, dramatically reduces estuarine circulation, largely preserving initial differences in ichthyoplankton production across the reserve boundary.; Bi-weekly ichthyoplankton surveys encompassing eight estuarine sub-basins were conducted from August 2002 to July 2004 to (1) characterize the regional ichthyoplankton species assemblage, and (2) document gradients in larval sportfish density across the KSC Reserve boundary. In total, 592,449 fish larvae from 58 taxa and 6.1 million eggs were collected. Catches were dominated by the families Engraulidae and Gobiidae which comprised 74% and 17% of larvae, respectively. The family Sciaenidae was the most speciose with eight taxa represented. Community structure was qualitatively similar throughout the region, although temporal variation in abundance was pronounced with 85% of eggs and 94% of larvae collected between May and October. Ocean-spawned larvae comprised <0.2% of captures. Eight sportfish taxa were recorded (2.7% of larvae), although 99% were of three sciaenid species: Cynoscion nebulosus, Sciaenops ocellatus, and Menticirrhus americanus, all likely estuarine-spawned. Without exception, larval densities for these species were higher outside the KSC Reserve, and predicted densities remained so even after a suite of measured environmental variables known to influence adult spawning and/or ichthyoplankton survival were accounted for.; Results suggest that habitat conditions (some unaccounted for in the sampling protocol), not current adult sportfish harvest rates, largely dictate local ichthyoplankton abundance. Potential explanations for observed distributions include enhanced larval survival in public areas due to elevated primary production, or decreased survival within protected areas due to bottom-water hypoxia near known sciaenid spawning sites. Although the KSC Reserve may not locally increase recruitment of estuarine-spawning sportfishes, it may still function as a regional source of ichthyoplankton by protecting offshore-spawning taxa during non-reproductive periods. |
