Nocturnal fish utilization of a subtropical mangrove‐seagrass ecotone

Abstract

Whereas diel fish migration between mangrove and seagrass habitats has been recognized for decades, quantitative studies have focused mainly on diurnal patterns of fish distribution and abundance. In general, previous studies have shown that fish abundances decline with increasing distance from mangroves; however, evidence for such a pattern at night, when many fishes are actively feeding, is scarce. The present study is the first to report nocturnal fish abundances along a continuous distance gradient from mangroves across adjacent seagrass habitat (0–120 m). Here, we used nocturnal seine sampling to test the null hypothesis (based on diurnal studies and limited nocturnal work) that fish abundance would decrease with increasing distance from shoreline. We focused on species and life‐stage‐specific abundance patterns of Lutjanus griseus, Sphyraena barracuda, Archosargus rhomboidalis, and Haemulon sciurus. Results indicated that assemblage composition and structure differed significantly by season, likely influenced by temperature. However, within each season, the fish habitat use pattern at both the assemblage and species‐specific level generally failed to support our working null hypothesis. Species‐specific analyses revealed that, for most species and life‐stages examined, nocturnal abundance either did not change with distance or increased with distance from the mangrove‐seagrass ecotone. Our results suggest that analyses where taxa are grouped to report overall patterns may have the potential to overlook significant species‐ and stage‐specific variation. For fishes known to make nocturnal migrations, we recommend nocturnal sampling to determine habitat utilization patterns, especially when inferring nursery value of multiple habitats or when estimating fish production.

Influence of predation risk and food supply on nocturnal fish foraging distributions along a mangrove–seagrass ecotone

“…Across transects, seagrass and macroalgae bottom cover was high (range: 66 to 96%) and depths were consistently shallow (range: 72 to 120 cm) out to 120 m from shore (Table 1). Seine net sampling also indicated that the composition and structure of fish communities were very similar among transects (Hammerschlag & Serafy 2010). Consistency in the above physical and abiotic characteristics among transects (Table 1) allowed us to minimize variation in environmental factors which could confound predator-prey relationships (e.g.…”

“…However, at night, many of these fishes disperse into adjacent seagrass beds to feed. This is supported by a variety of evidence including results from a combination of gut content analysis (Randall 1967), stable isotopes (Kieckbusch et al 2004, Nagelkerken & van der Velde 2004a, visual surveys (Rooker & Dennis 1991, Serafy et al 2003, seine sampling (Hammerschlag & Serafy 2010) and tagging investigations (Verweij & Nagelkerken 2007, Luo et al 2009). Nocturnal selection of seagrass beds by fishes as primary feeding sites appears to be related to elevated availability and accessibility of prey, many of which emerge from the vegetated substrate at night (Mattila et al 1999, Nagelkerken et al 2000, Unsworth et al 2007, Valentine et al 2007).…”

“…We selected juvenile gray snapper, bluestriped grunt and seabream because (1) these species are among the most easily identified fishes in our location; (2) each is representative of a different trophic guild (seabream -herbivore, bluestriped grunt -crustacean zoobenthivore, gray snappergeneralist zoobenthivore; Hammerschlag et al 2010b); and (3) two have economic importance in the region's recreational fishery and dive tourism industry (gray snapper and bluestriped grunt). We focused on individuals ranging between 10 and 25 cm in total length (TL) since this size class represents fishes that are best known to make diel movements among mangroves to seagrass habitats (Rooker & Dennis 1991, Nagelkerken et al 2000, Hammerschlag & Serafy 2010.…”

Abundancia y diversidad de la ictiofauna en la Reserva de la Biosfera Los Petenes, Campeche, Mexico: asociaciones con los ciclos nictimerales y las epocas climatica

“…Por otra parte, la variabilidad ambiental nictimeral es una fuerza acoplada a los ritmos circadianos de los organismos que modifica la estructura comunitaria tanto en abundancia como en diversidad, específica-mente por aspectos de alimentación (Gray et al, 1998;Castillo-Rivera et al, 2005;Oliveira-Neto et al, 2008;Hammerschlag & Serafy, 2010).…”

Coastal Habitats of the Gulf of Mexico

“…Short-term (e.g., diel or tidal) and long-term (e.g., seasonal or ontogenetic) migrations also commonly occur between adjacent coastal wetlands (e.g., mangroves and coral reefs), with nekton providing a source of connectivity and the transfer of production among otherwise isolated environments comprising more sessile species (e.g., Kneib 1997Kneib , 2000Deegan et al 2000;Ellis and Bell 2008;Hammerschlag and Serafy 2009;Jones et al 2010).…”