modifications to the harbor porpoise take reduction plan - Northeast ...

Observer data for gillnet hauls in the GOM between January 1, 1999 and May 31, 2007 are
analyzed in Appendix D (Palka et al., 2008). In all management areas, harbor porpoise bycatch
rates for hauls without pingers were greater than the bycatch rates of hauls with the required
number of pingers, confirming the effectiveness of pingers as a harbor porpoise deterrent when
properly deployed. The data indicate, however, that gillnet strings must have all of the required
number of pingers and those pingers must be working properly to effectively reduce harbor
porpoise bycatch. On average, nets with only 80% of the required number of pingers had
bycatch rates similar to nets with no pingers. Although the sample size is small, and the
operating conditions of the pingers are unknown, the data suggest that nets with fewer than the
required number of pingers had bycatch rates that were higher than nets with no pingers at all. A
possible explanation is that harbor porpoises may correlate a gap in pingers with a gap in the net
and try to swim through the portion of the net string that does not contain pingers. While the
present data are insufficient to examine this more closely, NMFS observers are collecting more
detailed information on the functionality of the pingers on nets surrounding a harbor porpoise
take. In summary, these findings confirm the need for regulations that compel fishermen to
properly install and maintain all necessary pingers, as well as the need for NMFS and the New
England states to continue outreach and enforcement efforts.
Mid-Atlantic
Assessment of the effectiveness of the individual gear modification requirements of the HPTRP
in the Mid-Atlantic is difficult, since many of the factors are interrelated. Palka et al. (2009)
analyzed observer data from the Mid-Atlantic gillnet fisheries between January 1, 1999 and May
31, 2007 (Appendix A) and identified a number of gear variables that appear to relate to a high
bycatch rate. However, many of these variables occur in the same nets. For example, large
mesh size, use of tie-downs, use of more anchors, and long soak times all occur in nets targeting
monkfish. In addition to these variables, net string length appears to relate to higher bycatch
rates in large mesh nets. Bycatch in large mesh hauled nets with string lengths greater than
4,000 ft (1,219 m) was three times higher than bycatch rates in hauled nets with string lengths
less than 4,000 ft (1,219 m). Currently, large mesh gillnet fishermen fishing between January 1
and April 30 (except during closure periods) in the Waters off New Jersey Management Area are
required to use nets strings that are no longer than 4,800 ft (1,463 m) in length, and strings no
longer than 3,900 ft (1,189 m) are allowed in the Mudhole Management Area during this period.
String length was the most common non-compliant factor identified in hauls observed in the
Waters off New Jersey, where 28 (65%) of 43 observed harbor porpoise takes were in noncompliant
gear, and 60% of all hauls observed were non-compliant.
Observer data displayed in Figures 3.2 and 3.3 in Appendix A (Palka et al., 2009) show a large
number of takes just south and east of the current Mudhole Management Area, outside the area
in which more restrictive gear modifications and closures are required. The bycatch analysis
identifies a strong relationship between a higher than average bycatch rate in the Waters off New
Jersey, including the Mudhole, and the water temperature of the observed haul (waters less than
43° F, ~6° C), water depths (164- 361 ft, 50 – 110 m), large mesh size, and location of the
observed haul. This analysis supports the seasonal requirements and location of the existing
Mudhole Management Area. However, it also identifies an area of high bycatch rates south and
east of the Mudhole Management Area that merits consideration for further restrictions.
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