Summary

Background and Objectives:

Deep sea coral and sponge ecosystems are widespread throughout most of Alaska’s marine waters. In some places, such as the western Aleutian Islands, these may be among the most abundant cold-water coral and sponge communities in the world. Because of the size and scope of Alaska’s continental shelf and slope, the vast majority of the area has not been surveyed for the presence of coral and sponge communities. Since the spatial distribution of these communities is not known in Alaska, it is difficult to predict the locations and types of human activities that may be threats to the deep-sea coral and sponge ecosystems. The objectives of this project were to predict the distribution of coral and sponge ecosystems for the eastern Bering Sea, Gulf of Alaska and Aleutian Islands.

Approach:

Historical bottom trawl surveys conducted by the RACE Division have collected data on the presence and abundance of corals and sponges in all areas of Alaska. We used data from 1996-2012 biennial bottom trawl surveys to examine the distribution and abundance of coral and sponge ecosystems. Generalized additive models based on the location (latitude and longitude), depth, slope, sediment, ocean current, bottom temperature and ocean color were used to predict the probability of presence of sponges corals and sea whips.

 

Significant results to date:

In the eastern Bering Sea about 61% of coral habitat was predicted to occur in slope areas (39% was predicted to occur on the outer shelf of the eastern Bering Sea; Figure 27). Of the slope areas, the highest amount of coral habitat was predicted to occur in Pribilof Canyon (33% of the predicted coral habitat occurs here). Only 1% of coral habitat was predicted for Zhemchug Canyon and the rest occurred primarily in the Pribilof-Zhemchug intercanyon area, in the Zhemchug-Pervenets inter-canyon area and in Navarin Canyon. This implies that about one third of the coral habitat predicted for the eastern Bering Sea occurs in Pribilof Canyon, an area that comprises only about 10% of the total slope area. In contrast, about twothirds of sponge (64%) and most sea whip (91%) habitat was predicted to occur on the outer shelf, an area that comprises about 82% of the total area of the slope and shelf examined. These results and analyses were published in Sigler et al. (2015) and validated in Rooper et al. (2016). 38 Figure 27. Predicted probability of presence or absence of coral, sponges and sea whips and sea pens from a generalized additive model (Sigler et al. 2015). In the Aleutian Islands the most important factors in determining coral presence or absence and abundance were location, maximum tidal current and slope. For sponges the most important factors determining presence or absence and abundance were location, maximum tidal current and depth. Coral and sponge were predicted to occur in relatively high abundance throughout the Aleutian Islands, but particularly in the areas surrounding Seguam Pass, Petrel Bank, and the area just to the east of Kiska Island (Figure 28). In the Gulf of Alaska corals and sponges are predicted to occur primarily along the shelf break and in hard-bottom areas of the Gulf, while sea pens and whips occur in large areas of the continental shelf (Figure 28).

 

Funding:

This project used existing data and required no funding from the DSCRTP. In kind contributions of time for the principal investigator was the only requirement. Coral Sponge Sea whips and pens 39 Figure 28. Predictions of the best-fitting generalized additive model for sponge, coral, Primnoidae, and Stylasteridae predicting the abundance (log-transformed catch-per-unit-of-effort (CPUE) or CPUE) in the Aleutian Islands (left) and pennatulaceans, corals and sponges in the Gulf of Alaska (right) bottom trawl surveys (Rooper et al. 2014, Rooper et al. in review).

 
Category:
  • Models
Type: DSCRTP Supported Date: 2015
Region(s):
  • North Pacific Council
Location(s):
  • Aleutian Islands
  • Bering Sea
  • Gulf of Alaska
Internal References:
  •  None Defined
 
Backlinks:
  •  None Defined