Frequency and success of ambush and chase predation in fish assemblages associated with seagrass and bare sediment in an Adriatic lagoon

Abstract

Predation of fish assemblages in seagrass meadows was examined in the field and in tank experiments. Lure trolling indicated that (1) total abundance of fish was higher on bare sediment where small fish (\5 cm), including juveniles, predominated; (2) abundance was lowest in seagrass where large fish ([15 cm) predominated; (3) large ambush predators, primarily the grass goby and European eel, were almost completely restricted to seagrass; (4) the predation mode in seagrass was almost entirely ambushing or stalk-attacking, while the predation mode on bare sediment was almost entirely chaseattacking; (5) ambush predation was far more successful than chase-attack predation; and (6) overall predation risk was approximately three times higher in seagrass. Tank experiments showed that piscivory success of the grass goby was higher than that of the most common chase-attacker, the black goby, and the presence or absence of artificial seagrass, regardless of density, had no significant effect on predation success of either species. Guts of the grass goby contained food items of a wider size range that averaged twice the size of those of the black goby. Our results confirm our prediction that the risk of predation, especially of small/juvenile fish, is higher in seagrass meadows than at adjacent bare substrate, and this risk differential is explained by the presence of larger, more efficient ambush predators restricted to seagrass, and the scarcity of large chaseattack predators in the Novigrad Sea.

Macrofaunistic Diversity in Vallisneria americana Michx. in a Tropical Wetland, Southern Gulf of Mexico

“…This is contrary to the general situation where an increase in habitat complexity, understood as a greater availability of microhabitats, favours a greater abundance and diversity of associated fauna (Heck & Wilson, 1987;York et al, 2006;Gullström et al, 2008). However, quantitative habitat complexity not always increase the relative habitat value of SAV (Seitz et al, 2006;Bogut et al, 2007;Florido & Sánchez et al, 2010;Schultz & Kruschel, 2010).…”

“…The batracoid Opsanus beta was the only species associated exclusively with SAV in Pantanos de Centla and seagrasses in other ecosystems (Schofield, 2003;Vega-Cendejas, 2004). The preference of the carnivore O. beta for epibenthic prey distributed in SAV and its stalking strategy are common in fish that are associated with this habitat (Schultz & Kruschel, 2010).…”

“…Among these habitats, submerged aquatic vegetation (SAV), harbour a high diversity of molluscs, macrocrustaceans and fish, by favouring a greater survival and growth of the associated populations (Minello & Zimmerman, 1991;Pelicice & Agostinho, 2006;Rozas & Minello, 2006;Cetra & Petrere, 2007;Genkai-Kato, 2007;Hansen et al, 2011). In structured habitats, as SAV, the faunistic diversity tends to be greater and mortality rate have a tendency to be lower than in non-structured habitats (Taniguchi et al, 2003;Gullström et al, 2008), although with exceptions (Bogut et al, 2007;Schultz & Kruschel, 2010). In particular, SAV in coastal ecosystems provides structured habitats that shelter a greater abundance and diversity of invertebrates and fish, where species use the habitat to obtain protection against predators, and as feeding and reproduction areas (Minello & Zimmerman, 1991;Rozas & Minello, 2006;Genkai-Kato, 2007;Hansen et al, 2011).…”

Underwater Seascapes

“…An intermediate tactic is used by the stalk-attack predator that actively searches for prey item. Once a prey is detected, stalk-attack predator approaches furtively until the prey is within the attack range, which is medium, and makes a speed burst to capture it (Matsuda et al 1993;Horinouchi et al 2009;Schultz and Kruschel 2010).…”

Use of a lure in visual census significantly improves probability of detecting wait-ambushing and fast cruising predatory fish

“…Stationary visual census of fish assemblages using baited cameras in the shallow benthos of Mediterranean rocky reefs resulted in higher counts of cruise-chase predators as compared to surface dwelling predators, while ambush predator density remained low (Stobart et al, 2007). Schultz and Kruschel (2010) showed for a Mediterranean Zostera bed that the visibility and detectability of the ambush predator Zosterisessor ophiocephalus was positively affected by mobile bait presentation. Cardona et al (2007), simultaneously conducting mobile experimental fishing and mobile visual census in Mediterranean Posidonia seagrass, found that a third of the visually detected taxa could be hooked, but that the majority of fish hooked (98%) were wait-chase and cruise-chase predators, these being two of the groups that are rare in visual census studies (Table 1).…”