Humpback Whales in Glacier Bay National Monument, Alaska Part 2

The increase in visitors and vessels to Glacier Bay is presented in Tables 6-8. (Data included in Table 6 cannot be compared to data presented in Table 7 because of difference in methods of data collection, sample area, time, effort, etc.)

Commercial fis.h.i.+ng vessel activity in the Bay was probably low until the 1970's. Since 1972 (it is not known whether data are available prior to 1972) commercial fis.h.i.+ng vessel visits have fluctuated (Figure 4), but fis.h.i.+ng activity has been greatest during the summer months (Figure 5). Sport fis.h.i.+ng visits have increased during the same time period (Figure 6).

[Footnote 4: This summary is based on information presented at the meeting by Mr. John Chapman and Charles and Virginia Jurasz.]

POSSIBLE CAUSE-EFFECT RELATIONs.h.i.+PS BETWEEN HUMAN USE OF GLACIER BAY AND THE DISPLACEMENT OF HUMPBACK WHALES FROM THE BAY[5]

The meeting partic.i.p.ants agreed that the observed decrease in the number of whales in Lynn Ca.n.a.l in 1974 and Glacier Bay in 1978 may be attributable to a number or combination of factors. Available evidence suggests human activity was at least one of the causes, or served to trigger otherwise "natural events". In Lynn Ca.n.a.l, humpback whales were known to feed on herring (_Clupea harengus pallasi_). In 1974, the year a herring fishery began, the number of humpback whales dropped to one (Table 1). Between 1974 and 1978 fis.h.i.+ng continued.

There was no fis.h.i.+ng in 1979.

Use of the Ca.n.a.l by Cla.s.s 5 vessels (cabin cruisers with high RPM outdrive units) increased by 15-20 percent each year after 1970 (Jurasz and Jurasz, 1979, p. 85). Three humpback whales were seen in Lynn Ca.n.a.l during the 1975-1977 seasons, the number increasing to five in 1978-1979. The relations.h.i.+p between vessel activity, fis.h.i.+ng effort, fish take, fish abundance, and the presence and activity of whales in Lynn Ca.n.a.l does not appear to be doc.u.mented.

In Glacier Bay, increased vessel traffic may be one of the factors responsible for the movement of humpback whales from the Bay in 1978 and 1979. The Juraszs' data, while not evaluated fully, suggest that there has been a general increase in avoidance by humpback whales of Cla.s.s 1 through 5 vessels over the three year period, 1976-1978.

TABLE 6. Number of visitors and vessels to Glacier Bay National Monument.[a]

--------------------------------------------------------------------- Cruise s.h.i.+ps Private Vessels Juraszs' (incomplete count) Year Visitation Increase Cla.s.ses 1-2 Juraszs' Cla.s.ses 4-8 ---------------------------------------------------------------------

1965 1,800 ---------------------------------------------------------------------

1969 16,000 789% over 1965 450 ---------------------------------------------------------------------

1970 29,700 86% over 1969 ---------------------------------------------------------------------

1972 33 ---------------------------------------------------------------------

1978 109,500 269% over 1970 123 1800 584% over 1969 ---------------------------------------------------------------------

1979 123 ---------------------------------------------------------------------

[Footnote a: Based on a table and information provided at the meeting by Mr. John Chapman, National Park Service.

(Modified by adding Juraszs' cla.s.ses of vessels.)]

TABLE 7. Number of vessel sightings per month in each cla.s.s as seen from the Juraszs' R/V GINJUR. (from Jurasz and Jurasz, 1979)

--------------------------------------------------------------------- 1977 1978 ---------------------------- ------------------------------- Vessel Cla.s.s June July August TOTAL June July August TOTAL ---------------------------------------------------------------------

1 20 22 11 53 17 25 8 50

3 67 18 6 91 62 31 64 157

4 37 42 30 109 29 125 64 218

5 38 45 17 100 27 61 24 112

6 3 14 0 17 0 29 19 48

7 6 4 6 16 8 4 5 17

8 7 2 7 16 2 12 3 17

12 4 3 7

TABLE 8. Average vessel sightings per day in each cla.s.s as seen from the Juraszs' R/V GINJUR. (Modified from Jurasz and Jurasz, 1979)

----------------------------------------------------------- Vessel Percent Percent Cla.s.s 1977 1978 Decrease Increase

1 3.90 3.20 18%

3 5.74 13.47 135%

4 8.38 16.87 101%

5 6.93 8.19 18%

6 1.11 3.99 259%

7 1.21 1.38 14%

8 1.24 1.18 5% -----------------------------------------------------------

[Ill.u.s.tration: Figure 4. COMMERCIAL FIs.h.i.+NG VESSEL VISITS TO GLACIER BAY (from Hale and Wright, 1979)]

[Ill.u.s.tration: Figure 5. COMMERCIAL FIs.h.i.+NG ACTIVITY GLACIER BAY (from Hale and Wright, 1979)]

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