Fecundity, Atresia, and Egg Size of Captive Atlantic Cod (Gadus morhua) in Relation to Proximate Body Composition

Abstract

Captive Atlantic cod (Gadus morhua) were fed at four ration levels (starvation, maintenance, moderate, and excess) for periods of 6–9 mo prior to and during spawning. At the end of the experiment, water, protein, glycogen, and fat contents of the liver, white muscle, and ovary were estimated. The depletion of the white muscle and liver was related to oocyte maturation and in particular to the proportion of eggs spawned (PES). The influx of protein into the ovary, the mean hydrated egg diameter, and the egg dry weight all reached maximum values at 10% PES and subsequently declined. Mean vitellogenic oocyte diameter was small prior to spawning but rose to a maximum at PES = 10%. Cod with high condition factors produced more previtellogenic oocytes and used a larger fraction during vitellogenesis. Actual fecundity of specimens deprived of food during the spawning period was between 20 and 80% of the potential fecundity depending on the nutritional status of the fish. Intensity of atresia in moderate ration fish increased from 0% at PES = 0% to 33% at PES = 80%. Estimates of durations of α-atretic vitellogenic oocytes varied between 10 and 13 d at 8 °C assuming a spawning period of 50 d.

Fisheries-induced evolutionary changes in maturation reaction norms in North Sea sole Solea solea

“…The same effect has been suggested in numerous other species (Kjesbu et al 1991, Trippel & Neil 2004 and is likely to be (partly) related to the storage of energy during the feeding period that can be metabolized later for reproduction (Rijnsdorp 1990). Although condition contributed significantly to variation in maturation, it could not explain the trends in the midpoints of the 2-dimensional maturation reaction norm over time: the decrease in Lp50 at any given value of condition (see Fig.…”

“…The length-based reaction norm is more reliably estimated than the weight-based reaction norm because of the ambiguity in data selection and corresponding interpretation for the weights (see below) resulting in a smaller data set and higher uncertainty in the reaction norm estimates. However, other factors in addition to size, such as body condition (Kjesbu et al 1991, Trippel & Neil 2004 or temperature (Dhillon & Fox 2004, Kraak 2007, may affect the probability of becoming mature.…”

“…It is known that the onset of maturation may be affected by condition (Kjesbu et al 1991, Trippel & Neil 2004 or other factors such as temperature (Dhillon & Fox 2004, Kraak 2007, in the juvenile period 1 or more years prior to first maturity. The influences of average temperature, condition and competitive biomass were analysed on the population level in the years before maturation.…”

Effects of Dietary Arachidonic Acid on the Reproductive Physiology of Female Atlantic Cod (Gadus morhua L.).

“…Body composition, especially with regards to fat, has a profound influence on oocyte recruitment, fecundity and atresia, as has been documented in Atlantic cod, both in wild-captured fish and experimentally (Karlsen et al, 1995;Kjesbu and Holm, 1994;Kjesbu et al, 1991;Marshall et al, 1999;Skjaeraasen et al, 2010). Studies on broodstock nutrition in cod, as well as other fish species, generally focus on the effect of diet on fecundity, egg and larval viability and biochemical composition of the eggs (Lie et al, 1993;Silversand et al, 1995;Røjbek et al, 2014;Hemre et al, 1995;Mangor-Jensen et al, 1994;Pickova et al, 1997;Salze et al, 2005;Izquierdo et al, 2001;Furuita et al, 2003;Mazorra et al, 2003;Lanes et al, 2012).…”

“…Cod eggs are small, and vitellogenesis takes place in the months immediately prior to spawning, as well as during the spawning period (Kjesbu et al, 1991(Kjesbu et al, , 1996a. The Atlantic cod is a periodic spawner, and each female can release 15-20 batches of pelagic eggs at 50-100 h intervals, during a period of 3-4 weeks (Kjesbu, 1989).…”