Biology and ecology of Nezumia liolepis and N. stelgidolepis from the west coast of North America

Abstract

Nezumia liolepis and Nezumia stelgidolepis were collected during a National Marine Fisheries Service 1997 groundfish survey along the Pacific coast of North America. Bottom trawling was conducted from 188 to 1260 m depths. Nezumia liolepis were collected from 581 to 1247 m (3·4-5·7 C) and N. stelgidolepis from 285 to 555 m (6·0-8·4 C). The two species had distinct depth and temperature distributions and the majority of the specimens for each species came from narrow depth ranges. Nezumia stelgidolepis attains a larger pre-anal fin length (117 mm) than N. liolepis (83 mm), and age estimates from otolith ring counts indicate ages from 3 to 9 years for N. liolepis and 7 and 13 years for N. stelgidolepis from specimens collected. The gonads of N. liolepis were not reproductively active, and a single N. stelgidolepis possessed eggs of various sizes suggesting batch spawning. N. liolepis and N. stelgidolepis fed benthically, primarily on crustaceans such as amphipods, shrimp, mysids and polychaete worms. Although diet overlap was high, these two species appear to limit competition for resources by habitat separation.

Reproductive biology of three gadiform fish species through the Mediterranean deep-sea range (147-1850 m)

“…In deep-sea gadiforms, the histological characteristics of the ovaries have only been described in C. rupestris (Alekseyeva et al, 1992;Kelly et al, 1996), Macrourus berglax (Eliassen and FalkPetersen, 1985;Murua and Motos, 2000), and partially in Nezumia stelgidolepis (Hoff et al, 2000). The fourth stages of development described here for P. blennoides, M. moro and L. lepidion are homologous at the first stages described in the above mentioned species.…”

Gill surface area and metabolic enzyme activities of demersal fishes associated with the oxygen minimum zone off California

“…The gadiform fishes consisted of the following two species: Nezumia liolepis, a small-bodied grenadier with a vertical distribution limited to OMZ waters (Hoff et al 2000), and Coryphaenoides acrolepis, a large-bodied grenadier with a peak abundance below the OMZ (Drazen 2007).…”

“…Gill half baskets were further dissected to separate and photograph the four individual arches. Images were used to determine the number and length of primary filaments, measuring every 10th filament for reasonable estimation purposes (Hughes 1984).…”

“…Midwater fishes which are OMZ transients do not rely on anaerobic metabolism, likely because of the energetically costly accumulation of lactate (Childress and Seibel 1998); therefore, it is unlikely permanent that OMZ dwellers would do the same (Seibel 2011). As in situ monitoring of oxygen extraction and demand is difficult for deep-sea fishes, approximations for these parameters can be determined from gill surface area (Hughes and Iwai 1978) and white muscle enzyme activities (Childress and Somero 1979), respectively.…”

“…Midwater fishes which are OMZ transients do not rely on anaerobic metabolism, likely because of the energetically costly accumulation of lactate (Childress and Seibel 1998); therefore, it is unlikely permanent that OMZ dwellers would do the same (Seibel 2011). As in situ monitoring of oxygen extraction and demand is difficult for deep-sea fishes, approximations for these parameters can be determined from gill surface area (Hughes and Iwai 1978) and white muscle enzyme activities (Childress and Somero 1979), respectively.Metabolic enzyme assays can be split into two major functional groups: enzymes within the citric acid cycle requiring chemically reduced oxygen to generate energy (e.g., malate dehydrogenase [MDH] and citrate synthase [CS]) and glycolytic enzymes dealing with pyruvate production (pyruvate kinase [PK]) and fermentation (lactate dehydrogenase [LDH]), which requires little to no oxygen at the expense of being less efficient. CS has been shown to correlate well with mass-specific oxygen consumption (Seibel et al 2000) and can therefore provide a reasonable approximation of aerobic metabolism.…”