Estimating and Applying Fish and Invertebrate Density and Production Enhancement from Seagrass, Salt Marsh Edge, and Oyster Reef Nursery Habitats in the Gulf of Mexico

Abstract

Seagrasses, oyster reefs, and salt marshes are critical coastal habitats that support high densities of juvenile fish and invertebrates. Yet which species are enhanced through these nursery habitats, and to what degree, remains largely unquantified. Densities of young-of-year fish and invertebrates in seagrasses, oyster reefs, and salt marsh edges as well as in paired adjacent unstructured habitats of the northern Gulf of Mexico were compiled. Species consistently found at higher densities in the structured habitats were identified, and species-specific growth and mortality models were applied to derive production enhancement estimates arising from this enhanced density. Enhancement levels for fish and invertebrate production were similar for seagrass (1370 [SD 317] g m–2 y–1for 25 enhanced species) and salt marsh edge habitats (1222 [SD 190] g m–2 y–1, 25 spp.), whereas oyster reefs produced ~650 [SD 114] g m–2 y–1(20 spp). This difference was partly due to lower densities of juvenile blue crab (Callinectes sapidus) on oyster reefs, although only oyster reefs enhanced commercially valuable stone crabs (Menippe spp.). The production estimates were applied to Galveston Bay, Texas, and Pensacola Bay, Florida, for species known to recruit consistently in those embayments. These case studies illustrated variability in production enhancement by coastal habitats within the northern Gulf of Mexico. Quantitative estimates of production enhancement within specific embayments can be used to quantify the role of essential fish habitat, inform management decisions, and communicate the value of habitat protection and restoration.

Underwater Video as a Tool to Quantify Fish Density in Complex Coastal Habitats

“…As productive coastal ecosystems continue to be modified with infrastructure and restoration efforts, it is critical to understand the functional roles of constructed or modified habitats in supporting fisheries species [31]. Quantitative estimates of fish densities across a range of habitats can guide the design of future infrastructure to maximize benefits for biodiversity [38], and support the derivation of production enhancement estimates in support of decision making [14]. The use of simple underwater video cameras for surveying fish communities is becoming widespread [17], yet the majority of studies derive only indices of relative abundance [19,29].…”

“…FoO and MaxN are logistically and conceptually simple metrics of relative abundance. However, they fall short of supporting the derivation of production enhancement estimates desired by many coastal resource managers and restoration practitioners for justifying and promoting management and restoration decisions [14]. Using our simple camera systems, we derived density estimates for the more abundant fisheries species from habitats that preclude the use of other quantitative sampling gears.…”

“…Similarly, many coastal habitat restoration and enhancement projects deploy artificial structures that attempt to mimic natural features, thereby providing habitat values for fisheries and other species [10][11][12]. Although many modifications of coastal areas tend to degrade habitat quality for fish [9], the addition of structurally complex artificial habitats into systems where the complex habitat is limiting may have incidental or intentional benefits for biodiversity and secondary production [11,13,14].…”

Concepts and Controversies in Tidal Marsh Ecology Revisited

“…These are outlined in detail within six core perspectives articles, which appear throughout the special issue. These articles open with Ziegler et al (2021), who provide a foundational appraisal of the key drivers of variation in tidal marsh structure and function that is observed in the literature. This is important, since tidal marsh studies are necessarily place based, but advancement of our understanding of these systems at a conceptual level relies on drawing out common themes in the structure and function of these systems across different geographic locations, at the same time as identifying the proximal factors that are responsible for this geographic variability.…”

“…These perspective articles are interspersed with contemporary case studies in support of the concepts outlined above. The structural and functional characteristics of tidal marshes are considered in several studies (James et al 2020;Jones et al 2020;Curran et al 2021;Kimball and Eash-Loucks 2021;Smith and Pellew 2021), supported with examples that apply contemporary approaches for exploring these characteristics (Bennett et al 2020;Baker et al 2021;Colombano et al 2021a;zu Ermgassen et al 2021a). System change within tidal marshes is considered in the context of factors that impact their health, resilience and productivity (Crosby et al 2021), and the implications for marsh nekton (Harris et al 2020).…”