Growth of early juvenile winter flounder (Pseudopleuronectes americanus Walbaum)

Abstract

Metamorphosis is a critical developmental stage in marine ¢sh species, but mortalities are also elevated at the settling phase. Our objective was to evaluate the e¡ects of di¡erent rearing systems and larval diets on survival, general condition and pigmentation of newly settled winter £ounder (Pseudopleuronectes americanus) juveniles. At settlement, winter £ounder juveniles were reared in two di¡erent types of tanks (plankton kreisel and rectangular raceway). The early juveniles were followed for 1 month and their condition was evaluated using biochemical indices. Juveniles did not show signs of ¢n rot and pigmentation was well developed, but they had di¡erent RNA/DNA ratios. This study highlights the fact that rearing conditions at the onset of the juvenile stage may be critical for successful juvenile production.

Assessment of paternal effect and physiological cost of metamorphosis on growth of young winter flounder Pseudopleuronectes americanus juveniles in a cold environment

“…Total protein content, which can be seen as an indicator of long‐term growth (weeks to months), is also a measure of energy storage since proteins can be used as an energy source, particularly under conditions of severe stress (Ferron & Leggett, 1994; Mommsen, 2001). In controlled conditions, de Montgolfier et al (2005) found protein:RNA ratios c. 15, which is similar to the values obtained in the present study and indicates a good synthesis rate. As an ultimate physiological response, survival was found to decrease slowly within the early juvenile stage; this was also found at the end of the metamorphosis in P. olivaceus (Gwak & Tanaka, 2001; Gwak et al , 2003).…”

“…This usually occurs in juvenile fishes (Mommsen, 2001) and represents an energy‐saving way of increasing size (Geffen et al , 2007). The RNA:DNA ratios observed here can be considered as low but are higher than ratios observed in starving early juvenile P. americanus reared in controlled conditions (de Montgolfier et al , 2005). In hatchery‐reared Japanese flounder Paralichthys olivaceus (Temminck and Schlegel), juveniles with ratios > 2 were considered to be in good condition while lower values corresponded to starving (from 1 to 2) or dying (< 1) juveniles (Gwak & Tanaka, 2001).…”

“…Measurements for L T , W M and standard length ( L S ) were made using Image Pro‐Plus 5.0 software (Media Cybernetics). Pigmentation and fin erosion were estimated using the qualitative methods described by de Montgolfier et al (2005). Fish manipulations were done according to the Canadian Council of Animal Protection recommendations and protocols approved by the University Animal Care Committee.…”

An RNA:DNA‐based growth model for young‐of‐the‐year winter flounder Pseudopleuronectes americanus (Walbaum)

“…The value of R RD has been shown to respond to alterations in feeding rate or food availability before the changes are detectable using conventional somatic growth measurements (Bastrop et al , 1991; Varnavskiy et al , 1992; Bisbal & Bengtson, 1994; Malloy & Targett, 1994 a, b ). The temporally sensitive and responsive nature of R RD ‐based growth estimates offer an accurate short‐term measurement of fish condition and have resulted in their widespread use in ecological field studies, stock enhancement projects, laboratory experiments and aquaculture applications (Rooker et al , 1997; Gwak, 2001; Gwak & Tanaka, 2001; Gwak et al , 2003 a, b ; de Montgolfier et al , 2005). Nucleic acid‐based measurements provide a viable alternative to other methods of tracking growth and nutritional condition, such as caging studies or otolith micro‐increment analysis.…”

Ontogenetic changes in nucleic acid, protein contents, and growthof larval and juvenile Japanese flounder

“…As for RNA concentration, it retained at high levels until 25 DAH, similar to the results found in plaice P. platessa larvae (Christensen and Korsgaard, 1999), and decreased sharply during the following days, revealing the involvement of hypertrophic and hyperplastic events. Many documents suggest that RNA/DNA ratio can sensitively respond to alterations in fish condition (Gwak et al, 2003a(Gwak et al, , 2003bYamashita et al, 2003;de Montgolfier et al, 2005;Mercaldo-Allen et al, 2006. As for protein/ DNA, it is a very useful index for assessing cell weight or cell size (Smith and Buckley, 2003;Caldarone, 2005;Park et al, 2008).…”