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.

Flem~sh C a p was dominated by the calanoid copepod Calanus finmarchicus It const~tuted 37 to 69 % of all zooplankton sampled with coarse mesh nets (0 333 and 0 505 mm) and 15 to 33 % In fine mesh nets (0 165 mm) dunng March to August O w~n g to its large size, C finmarchjcus dominated the biomass of all specles sampled in both coarse and fine mesh samples The domlnant copepod species in flne mesh samples (0 165 mm) were Oithona s~mllis and 0 atlanOca which together compnsed 20 to 4 2 O/a of all specles sampled C finmarcl~icus formed a d~screte populahon on Flemish C a p with peak spawning in mid-Aprll beginning first in waters 5 200 m depth Peak biomass occurred In late May and probably early June coincident w~t h peak abundance of late-stage copepodites Significant differences were observed in the rate of C finmarchicus developinent and absolute abundance among years sampled on Flemish Cap Differences in development were related to differences in the seasonal h e a t~n g of surface waters on Flemish Cap in different years It is hypothes~zed that these differences in rate of development and absolute abundance of C finmarchlcus and other copepods w~l l have a significant effect on larval fish feedlng, growth and survival

Tesseropora rosea of eastern Australia inhabits exposed, wave-washed rocks, is an extension feeder in fast currents, and has monometric growth, with orifice enlargement by erosion. It has a deep, mobile operculum. Tergal depressor muscles are large, scutal depressors moderately large. The opercular valves play an active part in respiratory pumping beat. Tergal depressors effect opercular withdrawal. Rostral scutal depressors assist in pumping beat. Lateral scutal depressors assist in opercular opening. Cim IV-VI of T. rosea unfurl rapidly in response to fast water currents and are captorial, either singly or in concert. The antenniform third maxillipeds (cirrus 111) turn back laterally in the extended position but fold over and hold down the captorial cirri in the curled position. Tetraclitella purpurascens of southern Australia inhabits crevices and overhangs on rocky shores, is an extension feeder in moderate currents, and has diametric growth, with orifice enlargement by circumferential growth of radii and parietes. It has a shallow operculum with only slight mobility. Tergal depressors are large, scutal depressors small. Valve action is mainly hinge-like and slow, with little apicobasal movement. The small scutal depressors assist the large tergal depressors in opercular withdrawal and have only a very minor role in pumping beat. Cirri IV-VI of T. purpurascens are held erect for long periods in moderate water currents. Captorial movements are similar to but slower than those of T. rosea. The third maxillipeds have short rami involved in forward food transfer. Setation correlates with function on the cirri of both species. The oral cone of T. rosea is broader and the mouthparts relatively larger than those of T. purpurascens, possibly mediating a more powerful triturating mechanism. A comparison of structure and function shows that T. purpurascens retains many primitive balanomorph features, whereas T. rosea has a more advanced functional configuration. In the evolution of tetraclitids, it seems likely that the tetraclitellines diverged early, before the austrobalanines gave rise to the tetraclitines. The four-plated wall may have evolved independently in tetraclitellines and austrobalanines.

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The Northwest Atlantic has been undergoing extensive ecosystem shifts involving oceanographic change and over-fishing. Capelin (Mallotus villosus), the focal forage fish species in this system, is a primary prey for most large predators, including cod, seals, whales and seabirds. Recently, the biology and behaviour of capelin has changed dramatically, although the basis for these changes is not well understood. Through a collaborative, multi-disciplinary research program among university, government and commercial fishers, we investigated mechanisms underlying these changes. In this manuscript we present an integrated overview of this initiative and synthesize key results from research carried out within the program. Our meso-scale study area encompassed the Funk Island Seabird Ecological Reserve, situated 60 km northeast of the Newfoundland coast. We identified 11 off-beach demersal spawning sites of capelin, which were primarily associated with small gravel in bathymetric depressions where temperatures were >2°C. Through comparisons of beach and demersal spawning, we described two distinct developmental strategies of eggs: high mortality and rapid development for beach sites versus low mortality and slow development for demersal sites. Emergence strategies of larvae at demersal sites also differed from beach sites elsewhere in Newfoundland. Integrating results from vessel-based and moored hydroacoustics (Acoustic Doppler Current Profilers) and biological sampling suggested that the diel vertical migratory patterns of capelin and its zooplankton prey are related. Capelin >120 mm total length migrated with larger, longer-distance (0-300 m) crustacean migrators (amphipods, euphausiids), whereas capelin <120 mm migrated with smaller, shorter-distance (0-100 m) migrators (copepods). These patterns influenced the diurnal feeding patterns of top predators. Vessel-based measures of observed seabird distributional patterns and trawl-estimated capelin availability and colony-based measures of seabird diets J. Northw. Atl. Fish. Sci., 39: 35-48. doi:10.2960/J.v39.m595 http://journal.nafo.int J. Northw. Atl. Fish. Sci., Vol. 39, 2008 36 revealed that seabirds are selective in their pursuit of forage prey and that they expand their foraging ranges considerably when capelin were less available in certain years. Furthermore, changes in the dietary composition of common murre (Uria aalge) can be linked to changes in the availability of capelin >100 mm, suggesting that the diet of common murre, and perhaps of other seabirds, has the potential for becoming a quantitative indicator of capelin status. Overall, this type of research framework will be important for moving toward ecosystem-based management approaches.