May 2008 Progress Report: NOAA cruise DY0807
The successful recruitment of fish larvae to suitable juvenile nursery areas is a necessary condition for growth,
energy storage, survival, and subsequently recruitment to the adult populations. Climate variability, which may
change existing meteorological and oceanographic conditions, will likely impact transport mechanisms between
these areas. Without a better understanding of these transport pathways, larval behavior during the transport
process, and delivery mechanisms (including settlement for flatfish), it will be impossible to predict the impact of
changing climate conditions on recruitment success to the adult populations.
Figure 1. Sampling grid.
We are working hard to get both the main
focus (NPRB and NPCREP) goals as well
as obtain samples for ancillary projects.
We began working over the Bering
Canyon/continental slope area (transects
BM & BJ, see Fig. 1) to obtain
Atheresthes spp. larvae for our BSIERP
project. We also collected larvae of
typical deepwater species: Bathylagus,
Leuroglossus, Reinhardtius,
Stenobrachius, and large numbers of
Sebastes. Although we obtained only 8
Atheresthes spp. larvae from our tows, it
was enough material for Ingrid Spies to
run and rerun and run again through the
bioanalyzer as she is optimizing the
genetics protocol for use at sea.
The equipment and optimized protocol are
working great. At this point the onboard results say that half of the larvae were Kamchatka and half arrowtooth flounder. She
is now using only one eye of each specimen for her analyses. Future collections will preserve the remainder of the fish in
Formalin (after removal of the eyeball) in the hopes that we can develop morphological / morphometric criteria to distinguish
the two species. We hope to get a few more samples for Ingrid on the way back to Dutch.
We then steamed up on to the shelf east of the 100 m isobath and began working our way westward towards Dutch Harbor.
We began finding eggs of Hippoglossoides elassodon (flathead sole) and Pleuronectes quadrituberculatus (Alaska plaice)
along transect Z. At stations close to the Alaska Peninsula, large numbers of fish eggs were collected by neuston gear. Most
of the eggs were a mixture of Theragra chalcogramma and P. quadrituberculatus; H. elassodon and smaller eggs of
pleuronectids were present also. The eggs are being reared onboard for Steve Porter’s net extrusion experiments on the next
cruise. Numbers of all larvae were low prior to the appearance of eggs in the neuston.
Soon afterward (transect AC), the rough counts of T. chalcogramma larvae began to increase. The highest numbers observed
so far (Friday evening) range from 347-705 per tow. The highest numbers were found on the AF & AI transects between
stations 7 and 13 on each line. Almost all T. chalcogramma larvae are in the yolk sac stage.
A satellite tracked drifter was deployed at station AF7 where we found 705 pollock larvae in one side of the bongo. Only 6
Pacific cod larvae have been observed on the shelf and all 6 were at station AF7. The large numbers of larvae encountered on
the AF and AI transects have been enabling us to save samples for Ron Heintz at AFSC/TSMRI for his BSIERP project. A 30
hr. series of MOCNESS tows to determine diel patterns in larval pollock vertical position will begin on Saturday.