Environmental variability in seagrass meadows: effects of nursery environment cycles on growth and survival in larval red drum Sciaenops ocellatus

Abstract

In their early larval stages, red drum migrate through coastal inlets and settle into shallow seagrass meadows within estuaries. This study describes environmental rhythms in red drum nursery habitats and evaluates their role in larval growth and survival to determine nursery habitat quality. Well-defined diel cycles were observed in temperature (amplitude 3 to 7°C) and dissolved oxygen (DO) (range 2.9 to 17.5 mg O 2 l -1 ), while sporadic cold fronts lowered temperatures by 6 to 10°C in 24 to 72 h. Groups of settlement and post-settlement larvae (3.9 to 17.3 mm standard length) were exposed in the laboratory to cycles of temperature and DO, and to combined temperature and DO diel cycles and then compared to fish grown in constant conditions (control). Relative to controls, growth was significantly reduced only in DO cycles with prolonged daily exposure to hypoxia (> 8.2 h d -1 ). Survival was similar in all treatments. In response to water cooling during simulated cold fronts, fish previously exposed to temperature cycles grew faster and had a higher food intake than control fish. Fish exposed to DO cycles maintained a greater food intake than control fish but grew at a similar rate. These results indicate that (1) diel cycles impart a physiological advantage to red drum larvae, (2) field measurements of environmental characteristics at a frequency of once a day may be inadequate for assessing nursery values for red drum, and (3) increased exposure to transient hypoxia in oscillating environmental conditions can affect growth and reduce nursery value and recruitment strength.KEY WORDS: Seagrass · Diel rhythms · Nursery quality · Hypoxia · Fish larvae · Growth · Red drum · Sciaenops ocellatusResale or republication not permitted without written consent of the publisher

The effects of diel-cycling hypoxia acclimation on the hypoxia tolerance, swimming capacity and growth performance of southern catfish (Silurus meridionalis)

“…The growth rate in mummichog (9 d, 9-100% oxygen saturation) (Stierhoff et al, 2003) and weakfish (Cynoscion regalis) (7 d, 18-100% oxygen saturation) (Stierhoff et al, 2009) in diel-cycling hypoxia showed no impairment. However, Atlantic salmon (S. salar) (23 d, 40-90% oxygen saturation) (Remena et al, 2012) and red drum (Dominguez et al, 2006) (2 weeks, 17-100% oxygen saturation) in diel-cycling hypoxia acclimation and Atlantic cod (Chabot and Dutil, 1999) (84 d, 45% oxygen saturation), turbot (42 d, 43% oxygen saturation) and European sea bass (42 d, 61% oxygen saturation) (Pichavant et al, 2001) in moderate hypoxia all showed decreased growth rates. The different growth results may be partly because of the difference in feeding regime, hypoxia degree and/or the experimental period of the different experiments.…”

“…However, the effects of mild hypoxia (for example diel-cycling and intermediate hypoxia) on feeding and growth have been shown to be species-specific (Bejda et al, 1992;Thetmeyer et al, 1999;Taylor and Miller, 2001). For example, mummichog (Fundulus heteroclitus) (Stierhoff et al, 2003) and weakfish (Cynoscion genus) (Stierhoff et al, 2009) showed no decrease in their growth rates under diel-cycling hypoxia acclimation, whereas Atlantic salmon (Salmo salar) (Remena et al, 2012), red drum (Sciaenops ocellatus) (Dominguez et al, 2006), winter flounder, (Pseudopleuronectes americanus) (Bejda et al, 1992), turbot (Scophthalmus maximus) and European sea bass (Dicentrarchus labrax) (Pichavant et al, 2001) all showed impaired growth rates because of a decreased feeding rate (FR). However, in Atlantic cod (Gadus morhua), both the FR and feeding efficiency (FE) decreased profoundly and led to more than a 50% decrease in the growth rate when reared in hypoxia, which was more sensitive than all of the above-mentioned fish species (Chabot and Dutil, 1999).…”

Seasonal variability in antipredator performance of red drum larvae

“…After 2 to 3 wk, planktonic larvae settle in nursery habitats such as seagrass meadows or marsh edges (Rooker & Holt 1997, Stunz et al 2002. Successive cohorts arrive at these habitats until early November, by which time water temperatures have dropped to about 20°C (Perez-Dominguez et al 2006). Significant unpredictability is superimposed upon this predictable seasonal change in temperature when sporadic low pressure meteorological fronts bring rapid drops in air temperature followed by gradual warming.…”

“…This is particularly relevant for a species such as red drum whose reproductive season happens over a period when temperatures drop more than 10°C (our Fig. 3a, Perez-Dominguez et al 2006). This temperature decrease is usually not entirely gradual because of unpredictable weather events that occur in the latter half of the season.…”

Batch spawning decreases competition among early life stages in coastal fishes: a simulation study using red drum Sciaenops ocellatus

“…obs.). The daily growth rate increased with temperature as: G = −0.0007T 3 + 0.0372T 2 − 0.1953T − 0.2202, where G is a percent daily increase of length and T is water temperature (°C) (Pérez-Domínguez et al 2006). After hatching, growth rate was randomly assigned hourly to each super-individual from a normal distribution with a mean of G and a standard deviation of 0.4G (derived from Pérez-Domínguez et al 2006).…”