38 
Fishery Bulletin 115(1) 
of misidentification, over-reporting, or underreporting 
(Burgess et al., 2005). Screening data removed many 
records that were likely inaccurate; however, some in- 
accuracies are not possible to readily identify and may 
have passed through the data screening process. Re- 
gardless of these concerns, immediate mortality and 
catch rates for the 2 species examined, blue and tiger 
sharks, closely match the rates reported in observer re- 
cords and by other sources. Accordingly, the inaccurate 
records that could not be identified were unlikely to 
have had a substantial effect on our results. 
Recommendations 
Although the USPL originally was designed to examine 
catch per unit of effort, if several additional variables 
were recorded in it, improved estimates of immediate 
mortality could be derived from this data set. Two ad- 
ditional categories, at-vessel alive and at-vessel dead, 
could be used to determine the number of animals that 
survive initial capture, and these categories would be 
required to determine factors that contribute to imme- 
diate mortality. An understanding of factors contribut- 
ing to immediate mortality (Frick et al., 2010a; Frick et 
al., 2010b; Dapp et al., 2016b) could help fisheries man- 
agers to make well-informed management decisions. 
This information can also be used by commercial fish- 
ermen to improve the quality of their catch by avoiding 
environmental or operational conditions that result in 
increased likelihood of death of sharks in catches be- 
fore the sharks are landed. 
Other changes to recording variables or to present- 
ing data in the USPL data set can be made to contrib- 
ute to our understanding of fisheries-induced mortality 
and catch rates in future studies. Some variables (e.g., 
soak time and other targeted species) that were record- 
ed in the USPL during the period examined were not 
made publicly available; a greater availability of these 
data would allow examination of additional, potentially 
important factors. Average gangion length was reported 
in the USPL, but we did not incorporate this factor into 
our analysis because lengths consistently were report- 
ed inaccurately (e.g., average gangion lengths >46 m 
were reported in 50% of longline sets). We are unsure 
why gangion length was often recorded inaccurately by 
fishermen, but a greater awareness of proper recording 
techniques for this variable could result in its use in 
future studies of immediate mortality. We recommend 
that 2 additional variables that can influence mortal- 
ity or catch rates, namely air temperature during haul- 
ing and estimated set depth, should be added to future 
USPL reporting forms. In addition, several other vari- 
ables that were not examined in our study but could 
influence catch and mortality rates have been included 
in recent iterations of the reporting form for the USPL 
(2015 form available from website; 2003 form available 
from website). These variables — bait used, hook type, 
hook size, and hook offset — should be incorporated into 
future analyses in which the USPL data set is used. 
There were 19 categories (species or groupings) of 
sharks that were recorded by fishermen in the UPSL 
data set (Table 1). Only 4 of these categories were 
considered for analysis because of problems with iden- 
tification and uncertainty about the accuracy of the 
recordings. The International Plan of Action for the 
Conservation and Management of Sharks outlined im- 
proved shark identification as one of its primary objec- 
tives and as a critical step to acquiring data to assess 
shark stocks (FAO^). We recommend that fishermen use 
shark identification guides or undertake shark identi- 
fication training (or both) to improve the accuracy of 
entries in the USPL data set for cryptic species and 
species that are similar in appearance to other species. 
We are the first to use the USPL data set to as- 
sess immediate mortality rates of longline-caught ti- 
ger and blue sharks. Rates of immediate mortality for 
these species closely match results from previous stud- 
ies, and this similarity indicates accurate recording 
by commercial fishermen (Table 2). Because the USPL 
data set covers the entirety of the US. Atlantic com- 
mercial longline fishery, it can be used to determine 
long-term changes in mortality over a wide geographic 
scale that may not be achievable with other data sets. 
If additional variables are recorded by commercial fish- 
ermen, the USPL data set can be used to accurately 
discern causes of mortality during fishery capture in 
a wide range of species. Although our analysis was re- 
stricted to examining bycatch of sharks, the inclusion 
of additional variables could allow for mortality exami- 
nations of targeted teleosts and targeted sharks over a 
vast temporal and spatial scale. 
The results of our study indicate the value of log- 
book data for scientific studies. In addition to providing 
immediate mortality rates, logbook data can be used to 
analyze catch rates, spatiotemporal catch trends, and 
species distributions (Cheng et al., 2001; Mandelman 
et al., 2008). The accessibility of the USPL data set to 
the general public promotes its use and advances our 
knowledge of fisheries science. Many other long-term 
government data sets have been collected, but they are 
not publicly available for analysis. Although we rec- 
ognize the legal requirements for the protection of a 
fisherman’s personal information, greater availability 
of governmental logbook and observer data would al- 
low for the examination of fishery trends on a world- 
wide scale and will be necessary to implement effective 
global strategies for species management. 
Our results indicate that fisheries management 
regulations have had a positive effect on the survival 
of the 2 shark species examined. The establishment 
of fin-to-carcass ratios has reduced the number of ti- 
ger shark discarded dead in the US. commercial long- 
FAO (Food and Agriculture Organization of the United Na- 
tions). 1999. International plan of action for reducing in- 
cidental catch of seabirds in longline fisheries. International 
plan of action for conservation and management of sharks. 
International plan of action for the management of fishing 
capacity, 26 p. FAO, Rome. [Available from website.] 
