[PDF-818.50 KB]
Details:
-
Personal Author:
-
Corporate Authors:
-
NOAA Program & Office:
-
Description:Entanglement in fishing gear is a known source of humpback whale, Megaptera novaeangliae, injury and mortality. However, reported events provide limited insight into entanglement frequency, risk factors and biological impacts. The caudal peduncle is commonly implicated in humpback whale entanglements and is consistently presented during the terminal dive. Since 1997, peduncle injuries have been studied annually as a relative index of entanglement frequency. Here we report on the analysis of injuries at the caudal peduncle and fluke insertion of 278 individual Gulf of Maine humpback whales in 2009. Preferred photographs were obtained while parallel to the whale and slightly ahead of its flukes during the terminal dive. Suitable images were examined for evidence of wrapping scars, notches and other injuries observed in documented entanglements. Of the individuals with comparable photographic coverage in 2008 (n=120), 12.5% ± 5.92% exhibited new scarring in 2009. Using another metric, 11.8% ± 3.80% of 278 individuals with suitable coverage exhibited unhealed injuries likely obtained within the prior year. Neither metric was significantly different from 2008, but it is likely too soon to detect the effects of recent mandatory changes in fishing practices aimed at reducing entanglement rates. Multi-state statistical models were also used to further study patterns and implications of entanglement injury acquisition. Modeling was based on individuals sampled Gulf of Maine-wide, 1997-2008. It included 1,688 annual encounters of 512 adults (272 females, 239 males) and 900 encounters of 643 known and suspected juveniles. The results to date support previous conclusions that 1) injuries are acquired more frequently by juveniles than by adults, 2) the sex of an individual does not consistently affect its likelihood of acquiring new injuries and 3) there has been little annual variation in scar acquisition rates over the past decade. However, modeling also revealed the possibility of lower juvenile survival after documented injuries as well as slight trends in annual entanglement rate (increasing for juveniles and decreasing for adults). We will further evaluate evidence for such effects when data from the 2009 and 2010 seasons are incorporated into this analysis.
-
Keywords:
-
Document Type:
-
Funding:
-
Place as Subject:
-
Rights Information:Public Domain
-
Compliance:Submitted
-
Main Document Checksum:
-
Download URL:
-
File Type:
