Analyses/Maps
Fish
National Marine Fisheries Service (NMFS) Trawl in the Midwater Environment
The
pelagic environment is home to many marine species at some stage
in their life. Therefore, it is important to document what species
interact in this environment, and determine environmental influences
on species abundances. Multivariate statistics were used to analyze
fish and invertebrate species assemblages caught in trawls conducted
at 7 and 30 meters depth between Cordell Bank NMS and Monterey Bay.
For more information on the neritic environment see the Ecological
Linkages Report section VII E. When determining species assemblages,
three separate analyses were completed: all data (1986-2001), only
1998 (warm year), and only 1999 (cold year). There were differences
between years in the species present, as well as in the organization
of species assemblages. The site groups identified were significantly
related to environmental conditions, but the influential conditions
varied between years. To investigate assemblages persistent over
more than one year, all of the data collected was analyzed for species
assemblages, but not for site assemblages due to the difficulty
in mapping assemblages through time as the same location may house
any number of assemblages depending on environmental conditions.
See Larson et al (1994) for a detailed analysis of rockfish assemblages
in response to short-term environmental variability. Through this
analysis a large amount of information has been condensed down to
assemblages of co-occurring species, as well as groups of similar
locations. Maps are provided to portray the spatial arrangement
of the site groups for 1998 and 1999.
Table. Average frequency of occurrence (percent occurrence calculated for each species and then averaged for each fish assemblage) of fish species assemblages for each midwater site group in 1998. Bolded numbers represent influential species assemblages within that site group.
| |
Site group A |
Site group B |
Site group C |
Site group D |
Site group E |
Site group F |
| N trawls |
15 |
20 |
14 |
5 |
11 |
26 |
| Myctophid Assemblage |
0.00 |
0.02 |
0.02 |
0.00 |
0.18 |
0.49 |
| Pacific Hake, juv. Assemblage |
0.40 |
0.17 |
0.31 |
0.40 |
0.76 |
0.62 |
| Stripetail Rockfish, juv. Assemblage |
0.13 |
0.08 |
0.55 |
0.00 |
0.18 |
0.15 |
| Market Squid Assemblage |
0.33 |
0.58 |
0.29 |
0.00 |
0.30 |
0.07 |
| Pacific Sanddab Assemblage |
0.27 |
0.10 |
0.07 |
0.07 |
0.12 |
0.01 |
Table. Average frequency of occurrence (percent occurrence calculated for each species and then averaged for each fish assemblage) of fish species assemblages for each midwater site group in 1999. Bolded numbers represent influential species assemblages within that site group.
| |
Site group A |
Site group B |
Site group C |
Site group D |
Site group E |
Site group F |
| N trawls |
23 |
7 |
9 |
21 |
16 |
15 |
| Pacific Hake, juv. Assemblage |
0.21 |
0.37 |
0.40 |
0.33 |
0.69 |
0.77 |
| Canary Rockfish, juv. Assemblage |
0.08 |
0.02 |
0.25 |
0.07 |
0.53 |
0.15 |
| Medusafish |
0.04 |
0.00 |
0.11 |
0.05 |
0.13 |
0.00 |
| Pacific Hake, adult |
0.04 |
0.00 |
0.00 |
0.38 |
0.06 |
0.00 |
| Pacific Saddab, juv. Assemblage |
0.40 |
0.14 |
0.30 |
0.34 |
0.19 |
0.27 |
| Market Squid Assemblage |
0.55 |
0.11 |
0.06 |
0.12 |
0.05 |
0.03 |
