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Hypoxia-induced structural changes in the diet of bottom-feeding fish and Crustacea
Pihl, L.; Baden, S.P.; Diaz, R.J.; Schaffner, L.C. (1992). Hypoxia-induced structural changes in the diet of bottom-feeding fish and Crustacea. Mar. Biol. (Berl.) 112(3): 349-361. dx.doi.org/10.1007/BF00356279
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Pihl, L.
  • Baden, S.P.
  • Diaz, R.J.
  • Schaffner, L.C.

Abstract
    Interactive effects of three alternating normoxia-hypoxia cycles on benthic prey exploitation by mobile fish (spot, Leiostomus xanthurus; and hogchoker, Trinectes maculatus) and a burrowing crustacean (Squilla empusa) were investigated in the York River, Chesapeake Bay, Virginia, USA, in 1989. Predators collected in four depth strata (A: 5 to 10 m; B: 10 to 14 m; C: 14 to 20 m; D:>20 m) variously affected by hypoxia were separated into size classes (three for spot and two each for hogchoker and mantis shrimp) to examine potential ontogenetic influences in prey selection. The most severe effects of hypoxia on the benthos occurred in the two deepest strata (C and D) and decreased in shallower strata (B>A), with Stratum A never affected by low oxygen. Predators investigated exhibited dietary evidence of optimal prey exploitation during or immediately after hypoxic events. In most instances gut contents contained significantly larger, deeper-burrowing prey during periods of low oxygen than during alternating peroids of normal oxygen levels. Spot consumed a greater biomass (45 to 73%) of polychaetes than other prey, with crustaceans initially also constituting a main dietary component but decreasing in importance later in the study period. The deep-burrowing anemone, Edwardsia elegans, was an important prey species for spot, particularly in the lower depth strata affected by hypoxia. Prey consumed by 10-to 15-cm-long spot increased significantly in size during some hypoxic events, suggesting a sublethal effect of hypoxia on large benthic species. Polychaetes (primarily Glycera americana, Notomastis latericeus and Loimia medusa) were dominant dietary components in hogchoker, making up between 85 and 98% of the diet. Bivalve siphons became important prey for hogchoker in the three deepest strata and were only consumed after the August hypoxia. Stomach contents of mantis shrimp were difficult to identify in most instances due to the near complete mastication of consumed prey. Crustaceans were important prey initially but became less conspicuous in the diet subsequent to the July hypoxia event, when hydroids became more dominant. Overall, predator species exhibited optimal exploitation of moribund or slowly recovering benthos affected by hypoxia. The sublethal effects of hypoxia through increased availability of benthos to resident predators can have important consequences for energy flow in areas such as the York River which experience periodic low-oxygen cycles.

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