Feeding ecology and condition of larval and pelagic juvenile redfish Sebastes spp.

Abstract

ABSTRACT. Eggs and nauplii of Calanus finmarchicus were the preferred prey types of redfish larvae whereas Oithona spp. copepodites were not, even though they were within the preferred size range. Significant seasonal and annual differences in larval diet of redfish resulted from differences in the availability of preferred prey. Seasonally, feeding was related to the succession of the spring dominance of C. finmarchicus to summer dominance of Oithona spp. Interannually, feeding was related to differences in the timing of spring spawning and temperature-dependent development of C. finmarchicus. Earlier spawning and faster development of C. finmarchicus, dependent on warmer water temperatures, resulted in poorer feeding conditions for redfish larvae. Under these conditions redfish larvae: (1) ate predominantly nauplii and copepodites of Oithona spp.; (2) ate less food by weight; (3) had lower relative body condition; and (4) there was a delayed size at metamorphosis from larvae to pelagic juveniles. Total prey concentrations between years did not determine better feeding and condition of redfish larvae, whereas the availability of preferred prey types did. Specifically, a lower abundance of C. finmarckrcus nauplii resulted in better feeding conditions than a higher abundance of Oithona spp. copepodites. These results emphasize that measuring total prey biomass within preferred prey sizes is not sufficient when evaluating larval redfish feeding conditions. There was a switch in diet for pelagic juveniles to include Oithona spp. copepodtes as preferred prey, in addition to copepod eggs and nauplu. T h s switch in diet coincided with changing prey availability due to the seasonal succession of zooplankton on Flemish Cap, Canada. Metamorphosis from larvae to juveniles at smaller sizes and younger ages is hypothesized to be advantageous to annual survival of redfish due to an increased foraging ability.

Interaction of pollinators and herbivores on plant fitness suggests a pathway for correlated evolution of mutualism- and antagonism-related traits

“…Herbivory studies, on their part, have frequently revealed extensive herbivory on flowers or developing fruits, a situation particularly frequent among perennial herbs such as H. foetidus (37)(38)(39)(40)(41). Nevertheless, reductions in seed production with respect to some maximum potential value due to herbivores or insufficient pollination do not necessarily have to influence plant population dynamics, because seed production may exceed the habitatspecific requirements for maintaining average plant density (42)(43)(44).…”

“…Both circumstances seem to be particularly common among herbaceous plants, which frequently experience devastating levels of flower and fruit herbivory (3, 37-41, 48, 49) by insect and mammalian herbivores that tend to be quite selective and concentrate on individuals with the larger floral displays and͞or fruit crops (17,18,41,50). We hypothesize that adaptive correlated evolution of mutualism-and antagonismrelated driven by correlational selection should be particularly frequent among herbaceous plants.…”

Precocious, selective and successful feeding of larval billfishes in the oceanic Straits of Florida

“…Daily ration estimates, as percent of gut-free body weight, given for minimum and maximum daylight lengths (duration of feeding) when billfish larvae are present during the protracted spawning season of approximately April to November trary to many studies that show a more constant increase in prey size, usually including shifts from copepod eggs and nauplii to calanoid copepodids and larger adults (e.g. Anderson 1994, Pepin & Penney 1997. Perhaps the most advanced first-feeding larvae are the coastal mackerels Scomberomorus spp.…”

Abundance and composition of zooplankton at Sitakunda coast of Chittagong, Bangladesh

“…Thus, their presence in numbers of zooplankton could have a serious effect on the recruitment of larval fish and could be very significant for the fish stocks and for the fishing industry. Houde and Lovdal (1982), Balbontin et al (1986) and Anderson (1994) presented that small zooplankton e.g. Copepods, Tintinnids, Cladocerans, larval molluscs etc.…”