732 
Fishery Bulletin 96(4), 1998 
£ 
25 
20 
15 - 
10 - 
5 - 
Entanglement 
No Entanglement 
100-105 106-110 111-115 116-120 121-125 126-130 
Length (cm) 
Figure 4 
Frequency distribution of the lengths of stranded harbor porpoise, Phocoena 
phocoena , carcasses showing evidence of entanglement, no evidence of en- 
tanglement, or carcasses for which evidence of entanglement could not be 
determined owing to advanced decomposition of the carcass. 
of death, and our documentation of 
entanglement was conservative. In 
addition, it is likely that not all ani- 
mals entangled in nearshore gill nets 
reached the beach. 
Detailed examination of stranded 
carcasses can be a useful means of 
identifying bycatch of harbor por- 
poises, and other marine mammals, 
in nearshore gillnet fisheries. This 
method is not, however, a surrogate 
for at-sea observer programs that 
monitor bycatch rates. The gillnet 
fisheries that operate along the 
coastal waters of the Mid-Atlantic are 
diverse, complex, and their activities 
poorly documented. An observer pro- 
gram is necessary to provide an unbi- 
ased estimate of the number of animals 
killed in these fisheries, so that a com- 
plete assessment can be made of this 
anthropogenic source of mortality. 
Accurate assessment of carcasses 
requires consistent and conservative 
use of an objective protocol, such as 
that described by Haley and Read 
( 1993), by trained stranding network 
personnel. The process of transporting, freezing, and 
thawing carcasses may obscure subtle evidence of 
entanglement, so it is important for experienced ob- 
servers to examine fresh carcasses. At the necropsy 
workshops, for example, we were unable to assess 14 
carcasses that were previously scored as entanglements 
when examined fresh on the beach. 
All stranded porpoises were young and sexually 
immature. Interestingly, however, both mature and 
immature porpoises have been taken by gillnet fish- 
eries operating in the Mid-Atlantic. Most of these 
observed bycatches have been recorded at some dis- 
tance from shore, suggesting that some age-based 
segregation occurs in this population during winter. 
An alternative explanation is that adult porpoises 
captured in gill nets do not wash ashore. This latter 
explanation seems unlikely for two reasons. Because 
of their larger size, carcasses of adults should be more 
likely to reach shore intact than those of juveniles. In 
addition, most ( 17 out of 24) of the observed porpoises 
taken as bycatch in the Mid-Atlantic were tagged be- 
fore being discarded; none of these tagged porpoises 
have subsequently washed up on the beaches. Thus, it 
appears that only juvenile porpoises are present in the 
nearshore waters of the Mid-Atlantic during winter. 
The proportions of code-2 and code-3 stranded car- 
casses were not significantly different in the samples 
of nonentangled and entangled porpoises, indicating 
that the carcasses of porpoises killed in fisheries were 
likely originating at similar distances from shore as 
those animals dying of natural causes. In addition, the 
lengths of entangled porpoises were similar to those 
that died from other means. All stranded porpoises, 
entangled and nonentangled, were from the same seg- 
ment of the population — young animals in nearshore 
waters. The distinguishing feature of these two samples 
is that a larger proportion of the nonentangled animals 
were emaciated, indicating that they may have died of 
starvation, whereas most of the entangled animals were 
in good body condition when they died. 
The majority of strandings were reported in Vir- 
ginia, but this may be due in part to the regular 
monitoring of beaches in the southern portion of this 
state. The beaches of Virginia are patrolled fre- 
quently by stranding network personnel; therefore 
stranded porpoises are discovered soon after they 
appear on the beach. In Maryland beaches are pa- 
trolled daily by national and state park personnel. 
Lower numbers of stranded harbor porpoises in 
Maryland, therefore, likely reflect lower abundance 
or different fishing effort and hence fewer strandings 
in this area. The Outer Banks of North Carolina, by 
contrast, have not been patrolled frequently, result- 
ing in fewer reports of stranded porpoises. The con- 
dition of harbor porpoise carcasses retrieved in North 
Carolina was poor in relation to those retrieved in 
