Paula E. Whitfield

Abundance estimates of the Indo-Pacific lionfish Pterois volitans/miles complex in the Western North Atlantic

Less than a decade after being observed off Florida, the invasive Indo-Pacific lionfish is now widely distributed off the southeast coast of the United States. As a step towards measuring invasion impacts to native communities, we examine the magnitude and extent of this invasion by first, compiling reports of lionfish to provide range information and second, estimate lionfish abundance from two separate studies. We also estimate native grouper (epinepheline serranids) abundance to better assess and compare lionfish abundances. In the first study we conducted SCUBA diver visual transect surveys at 17 different locations off the North Carolina coast in water depths of 35–50 m. In the second study, we conducted 27 Remote Operated Vehicle (ROV) transect surveys at five locations from Florida to North Carolina in water depths of 50–100 m. In both studies, lionfish were found to be second in abundance only to scamp (Mycteroperca phenax). Lionfish were found in higher abundance in the shallower North Carolina SCUBA surveys (\(\bar{x}= 21.2\) ha−1) than in the deep water ROV surveys (\(\bar{x} = 5.2\) ha−1). Lionfish reports continue to expand most recently into the Bahamas, raising the specter of further spread into the Caribbean and Gulf of Mexico. The potential impacts of lionfish to native communities are likely to be through direct predation, competition and overcrowding. The high number of lionfish present in the ecosystem increases the potential for cascading impacts throughout the food chain. Within the southeast region the combined effects of climate change, overfishing and invasive species may have irreversible consequences to native communities in this region.

MODELING SEAGRASS LANDSCAPE PATTERN AND ASSOCIATED ECOLOGICAL ATTRIBUTES

A predictive model for seagrass bed coverage (presence/absence at 1-m res- olution) and ecological attributes of the bed, such as biomass and shoot density, would be a valuable management tool. But forming such a predictive model is complicated by a number of factors that strongly influence seagrass bed structure and our interpretation of its ecological function. The factors include the effects of waves and water depth (hydro- dynamic setting) and the spatial and temporal scales of the sampling technique itself. In this study, we examined the coherence of predictions of seagrass cover and ecological attributes of temperate, mixed-species seagrass derived from two common sampling tech- niques, (video) line transect (commonly used by biologists) and grid-sampled surveys (often used in remote sensing). Mapping resolution was held constant at 1 m, and the two tech- niques applied across seagrass beds of varying coverage that reflected the effect of a hydrodynamic gradient ranging from patchy, high-energy beds to continuous cover, low- energy beds. We found that the prediction of seagrass coverage as a function of hydro- dynamic setting can be improved not only by increasing the spatial extent of sampling at a fixed resolution (1 m), but also by ensuring that data for both dependent (e.g., percent cover) and independent (e.g., wave exposure) variables are averaged over similar scales (spatial extent and resolution). Large-scale features of the landscape, such as patches several meters in width, appeared to be best quantified by sampling over a large spatial extent, as with the video transects. Therefore, contiguous sampling over a broad spatial extent, as opposed to our numerous, somewhat smaller sampling (grid-sampled, 50 3 50 m areas) is the more appropriate strategy for predicting the probability of seagrass bed cover. Con- versely, we found that ecological attributes of the seagrass bed (biomass, shoot density, and sediment composition) were best characterized by sampling over a shorter spatial extent (i.e., ,50 m), indicating that very localized conditions may have influenced patterns of seagrass community attributes. Generalizing information about seagrass bed ecological attributes obtained from high-resolution samples (fine scale) taken over a broad spatial extent (coarse or landscape scale), as may occur with resource surveys and impact assess- ments, has the potential to be highly misleading, especially in patchy environments. The influence of sampling scale and survey method on the prediction of coverage and ecological attributes of seagrass beds reveals the need to carefully choose sampling designs to evaluate seagrass distribution and their associated ecological characteristics in the Beaufort, North Carolina (USA) area, and perhaps in other like habitats.

Distribution and Identification of an Invasive Gracilaria Species that is Hampering Commercial Fishing Operations in Southeastern North Carolina, USA

A newly abundant Gracilaria species in the sounds of southeastern North Carolina has become a problem for commercial fishing and industries drawing water from the lower Cape Fear River. DNA sequence analyses have shown that this species is Gracilaria vermiculophylla, a taxon originally described from East Asia. Surveys for G. vermiculophylla have shown that it has a discontinuous distribution in the sounds of southeastern North Carolina, and suggest that it is spreading. Gracilaria vermiculophylla meets 6 of the 10 criteria used to help identify invasive species in that it has only recently appeared in southeastern North Carolina; is associated with human mechanisms of dispersal; has a restricted distribution; has disjunct populations in isolated oceans; no means of active dispersal, and an exotic evolutionary origin. The species may also meet two additional criteria as its local range is believed to be expanding, and it is filling a previously unoccupied seasonal niche. These factors taken together strongly suggest that G. vermiculophylla is an invasive species in southeastern North Carolina.