Draft February
Injury Frequency for Discarded
Paralichthys dentatus
Summer Flounder Paralichthys dentatus
in the Recreational Fishery
of the Mid Atlantic Bight
In uence of Landing Size Regulations
1
N Powell Eric
1
Eleanor A Bo chenek
2
DePersenaire John
1
Sarah E King
1
Shell sh Research Lab oratory Haskin
Institute of Marine and Coastal Sciences
Rutgers The State University of New Jersey
Miller Ave
Port Norris NJ
USA
2
Alliance Recreational Fishing
B South New York Road
Gallo way NJ
Keywords Paralichthys summer ounder recreational shery discard mortality
sheries management health index size limit injury frequency
Running Head Injury frequency for discarded summer ounder
Abstract
Summer ounder Paralichthys dentatus supp orts an imp ortant recreational
shery along the northeast coast of the United States Successful rebuilding of the
sto ck and the need to constrain landings within total allowable landing targets has
resulted in declining bag limits and increasing size limits Concurrent unwanted
outcomes of these regulations include the increased rate of summer ounder dis
Draft February
carding and the reduction in satisfaction derived from recreational shing trips A
series of shing trips were observed in which alternative management scenarios were
tested to identify approaches to b etter optimize regulatory constraints through the
use of bag limits and size limits The alternatives included a slot limit in which some
smaller sh were allowed to b e landed a reduced minimum size and a cumulative
size in which the bag limit and size limit were con ated such that sh take was
controlled by the cumulative size of the landed sh
The control or legal scenario pro duced higher injury frequencies than
other shing scenarios due to discarding of larger sh that tended to b e gut ho oked
Two alternatives p erformed signi cantly b etter in terms of reducing the p otential
for discard mortality among discarded sh the slot limit and the cumulative size
scenarios An intermediate p erformance of the reduced minimum size scenario was
due to an increased prop ortion of dead sh but this asso ciation was unexplained
Fish uninjured saved for minor ho ok damage were common on all vessels and in all
shing approaches Injury frequency was in fact remarkably low less than half
of the assumed discard mortality rate in present day sto ck assessments The study
supp orts the use of size sp eci c mortality rates for sh discarded recreationally
no supp ort for the e cacy of the management system in The study o ers
controlling discard mortality rate Simply put the present day regulatory plan
maximizes discards while simultaneously maximizing the discard of injured sh less
likely to survive Any of the alternative plans is an improvement but the slot limit
and cumulative size scenarios are deserving of the most scrutiny
Intro duction
Summer ounder Paralichthys dentatus is an imp ortant commercial and
recreational shery along the northeast coast of the United States from North
Carolina to Massachusetts Summer ounder is one of the most sought sh by
consumers of seafo o d Burger et al and accounts for a substantial fraction of
angling trips by Mid Atlantic Bight anglers Terceiro Summer ounder
was seriously over shed in the late s to early s Terceiro A
sto ck rebuilding program b egan in the early s that ultimately resulted by
in the return of spawning sto ck biomass to near historically high levels
Terceiro although the most recent assessment found the sto ck to remain
Draft February
in an over shed state Nevertheless the degree and rapidity of rebuilding of
the sto ck is noteworthy This remarkable accomplishment did not come without
vexations however Achieving target shing removals was readily accomplished for
the commercial sector by monitoring landings referenced to a total allowable landing
limit Achieving the same for the recreational shery proved a more formidable
task For the recreational shery as in the commercial shery allo cations are
based on biomass but for the recreational shery regulation of take is based on
the landing of individual sh Reliance was placed on mo dulating the time honored
limitations on take bag limits and size size limits Size limits help restrain
total landings but also are instrumental in expanding size frequency distributions
truncated by over shing The p otential for size frequency truncation by recreational
see also Richardson et overharvesting is do cumented e g Schro eder and Love
al and the impact of commercial harvesting on the size frequency distribution
is well describ ed e g Greenstreet and Hall Rago et al Richardson et
al Coincident with the rebuilding of the summer ounder sto ck has b een
the establishment of a more normal distributed size frequency distribution from
the seriously truncated state of the early s Terceiro
For summer ounder overages wherein yearly landings exceed targets b ecame
commonplace in the recreational shery despite increases in size limits and reduc
tions of bag limits In no small measure the increasing sto ck size militated against
successful constraint of the recreational shery through the increased abundance
and availability of legal sized sh to the angling public Concomitantly and accord
ingly as bag limits were reduced and size limits increased to constrain landings the
numb er of sh caught and discarded necessarily increased By discards had
reached a signi cant fraction of total catch and discard mortality although a small
fraction of total discards had b ecome an imp ortant source of total mortality for
the sto ck exceeding that of the commercial shery by nearly a factor of four Ter
ceiro Simultaneously as most of the summer ounder recreational shery
is consumptively motivated the quality of the shing exp erience achieved by the
recreational angler decreased as the numb er of sh kept b ecame a small fraction of
total catch and as sh of the size allowed to b e landed b ecame rarer inshore where
the ma jority of the angling public shed
Draft February
The problem of discards in sheries management is well do cumented and widely
discussed e g DeAlteris et al Murawski Jennings and Kaiser
Halliday and Pinhorn Discards issue from regulatory control e g Coleman
et al Powell et al Bo chenek et al but also through the
approach to and economics of shing e g Gillis et al Stratoudakis et al
Salthaug and Aanes Much attention has b een fo cused on discard
mortality in the commercial sector e g Suuronen et al DeAlteris and
alley Maguire et al much less attention has b een fo cused on La V
the mortality asso ciated with recreational discarding e g Render and Wilson
Monaghan and Ross Coleman et al As a consequence of the
plethora of unintended rep ercussions from the institution of regulations decreasing
bag limits and increasing size limits we carried out a series of exp eriments designed
to test the e cacy of three alternative management plans Each varied either size
limits or the relationship of size limits to bag limits with the target of converting
discards into landings while retaining constraints on harvest required under total
included the landing of a certain numb er of sh allowable landing goals Options
b elow the normal legal size under a de ned bag limit and the con ation of bag
limits and size limits by restricting the cumulative size of landed sh Bo chenek et
al submitted describ e the impact of each scenario on the discard to catch ratio
Here we evaluate the frequency of injury among sh discarded under each of the
exp erimental plans to determine if varying the approaches to bag limits and size
limits can b oth reduce discards and also discard mortality while improving the
angling exp erience by retaining or increasing landings
Metho ds
erimental Design Exp
Four shing scenarios were compared a reduced minimum legal size limit
set at under the legal bag limit a slot limit in which anglers were
allowed to keep two sh b etween and the state sp eci ed minimum size limit
a cumulative size limit in which the state sp eci ed bag limit and size limit
were con ated to pro duce a cumulative size limit for sh for New Jersey
and the legal bag for example this was obtained as sh
limit and size limit hereafter termed the control condition The control conditions
Draft February
varied b etween states For New Jersey in the bag limit was eight sh and
the legal size was For New York the bag limit was four sh and the
legal size was Subsequent statistical analyses did not resolve any in uence
of the di erence in regulatory control b etween states and thus control trips were
not further distinguished Fourteen inches was selected as the minimum size for
the exp erimental trips b ecause this was the minimum size limit for the commercial
shery in
essels and Lo cation V
The study to ok place during the shing season of using party b oats from
New Jersey and New York Details are provided by Bo chenek et al submitted
Five vessels were selected to encompass the variation in vessel sizes and areas shed
along the coasts of New Jersey and Long Island New York with three vessels from
homep orts in New Jersey and two vessels from homep orts in New York These
vessels covered the range of party b oat activity along this stretch of coastline shing
inshore in state waters o shore in federal waters and in lago ons and estuaries The
vessels covered a range of sizes and angler capacities from a lower limit of anglers
to a maximum of Bo chenek et al submitted provide detailed descriptions of
these vessels The lo cations of the shing trips observed for this study are shown
in Figure The four shing scenarios were observed on each vessel three times
with observations o ccurring in the early middle and late phases of the shing
season b eginning in June and nishing in Septemb er of Each observation
encompassed a full day trip or two half day trips morning and afterno on Catch
statistics for these trips are provided by Bo chenek et al submitted
Assessment Health
On each drift of each trip onb oard observers recorded the condition of as many
sh as could b e observed and noted whether these sh were kept or discarded Total
length of each observed sh was measured to the nearest The observed sh
included the vast ma jority of all sh caught although o ccasional p erio ds of rapid
capture of sh may have resulted in some sh haphazardly b eing excused from
observation No sh known to have b een caught escap ed observation however
Additionally captains recorded the b eginning and ending times and p ositions of
Draft February
each drift
Observers were unable to follow released sh As a consequence health co des
were develop ed that ranked sh according to obvious damage and that re ected an
anticipated likely increase in the risk of mortality We recognize that sh recover
from even mild capture and release slowly often over a p erio d of weeks Bouck
and Ball Pickering et al Haux Sj ob eck and Larsson Fish were
describ ed as healthy bleeding gut ho oked and or dead A healthy sh was a sh
with no obvious injury save for mild damage in the mouth region due to ho oking
Gradations were achieved by combining certain of these observations For example
a sh with minor bleeding but otherwise healthy was describ ed as b oth healthy and
bleeding Observers provided these ratings for each kept and discarded sh
The observations of injuries and assessments of health were later combined
into a to p oint morbidity scale and an injury scale The morbidity scale was
de ned as follows All sh observed to b e healthy without additional comment were
judged to b e in GOOD condition Upp er case denotations identify categories
in subsequent gures parenthetical numb ers assign semiquantitative rankings for
statistical analysis Fish with injuries noted but still describ ed as healthy sh
with minor bleeding for example were given an overall morbidity rating of NWEL
not well Fish describ ed as bleeding or gut ho oked were given the next lower
morbidity rating of ILL Fish b oth bleeding and gut ho oked were judged to b e
moribund MORB Fish identi ed as DEAD were so judged The to
p oint morbidity scale provided a ranking for each observed sh from sh apparently
uninjured b eyond minor damage due to ho oking to sh that were dead that could
b e analyzed statistically The injury scale fo cused on the typ e of injury observed
and was inherently categorical rather than semiquantitative This scale assigned
sh to ve categories Those without observed injury b eyond minor damage due to
ho oking were assigned to the uninjured category NONE Gut ho oked sh were so
describ ed GUT Fish bleeding were assigned to that category BLED Fish b oth
bleeding and gut ho oked were so describ ed BGUT The latter three conditions
were assigned regardless of whether the sh was living or dead at the time of
observation If a sh was dead but no injury was noted it received a deceased
co de DECD Finally we assigned sh to a binomial health index of WELL or
Draft February
unwell SICK by assigning any sh with any noted injury to the latter The
health index was also analyzed statistically
Trip and Catch Descriptors of
Drifts were assigned to either foreno on AM or afterno on PM categories
Time of day for statistical analysis referenced these two categorical variables E ort
was calculated as the pro duct of the numb er of anglers p er vessel and the cumulative
elapsed time of the drifts for each trip and time of day Bo chenek et al submitted
describ e the use of this e ort measure rather than one that fo cused on the
cumulative distance of each drift Catch rate did not in uence e ort as has b een
observed elsewhere Miranda Fish were assigned to a series of inch length
classes for statistical analysis with the upp er class b oundary falling in the higher
class L L L L L
L L and
Statistical Analysis
In every case analyses were conducted separately for kept and discarded sh
Statistical analysis followed a bipartite path The relationships of the morbidity
index and the binomial health index with the main e ects of vessel time of day
shing scenario and length class were evaluated using ANCOVA E ort and depth
were included as covariates Initial investigation p ermitted the elimination of
most pairwise interaction terms the exceptions b eing the interaction of vessel and
shing scenario and vessel and time of day Thus overall pairwise interactions
were rarely signi cant Tukey s Studentized Range Tests were used to evaluate the
lo cation of signi cance within signi cant ANCOVAs As interaction terms were
rarely signi cant these tests were relatively reliable indicators of the rankings of
category states however the reader is cautioned nevertheless concerning the use of
osteriori tests when interaction terms are signi cant a p
In several cases where signi cant interaction terms o ccurred b etween two main
e ects we followed up the primary ANCOVA with a more limited analysis targeting
one of the two main e ects analyzed sequentially for each of the second main
e ect states Where appropriate additional main e ects and interaction terms
were retained in the subsidiary analyses
Draft February
The design of the shing alternatives p ermitted the retention of sh smaller
than the legal size in force in We anticipated that discard mortality would b e
a ected by any di erential in injury prop ensity b etween length classes To identify
variations in the size frequency of discards we describ ed the discards of each trip
in terms of descriptors of the size frequency distribution namely the mean size
th th th
and p ercentiles of size for sh discarded and their discarded the
interquartile range Each was used as a dep endent variable in ANCOVA with vessel
time of day and shing scenario as main e ects Depth and e ort were included
as covariates as well as interaction terms that preliminary analysis indicated on
o ccasion were signi cant
In addition corresp ondence analysis Claussen was used to visualize the
relationship of certain main e ects with morbidity and injury class Corresp ondence
analysis is a data reduction technique that p ermits evaluation of correlational
relationships within categorical datasets e g Green Ghertsos et al
analogous to principal comp onents analysis for continuous or meristic sensu Sokal
and Oden data For this purp ose depth and e ort were also converted into
p olytomous variables as follows Drifts were assigned to four depth categories
ft Z ft Z and ft Z E ort was assigned to ft Z
a series of e ort categories HIGH angler hours mo derately high MHGH
angler hours mo derately low MLOW angler hours and LOW
angler hours Again in each case the upp er class b oundary of intermediate states
was assigned to the higher category
Corresp ondence analysis used as primary data sources vessel time of day
shing scenario length class and the categorical variables for e ort and depth
That is axes were de ned based on descriptors of the trip not descriptors of sh
health Supplementary variables p ositioned on the axes thusly de ned included the
morbidity index the injury index and the health index
Results
The numb er of trips tows anglers p er trip an other descriptive metrics of the
shing exp erience are provided by Bo chenek et al submitted Here we examine
the relationship of the health and morbidity indices on descriptors of the trip
Draft February
shing scenario and catch The health index was a binomial index discriminating
injured or dead sh from those without apparent injury The morbidity index was
a to p oint ranking of sh health from apparently uninjured to dead Several
variables rarely in uenced sh health Table These included time of day e ort
the interaction of vessel and time of day and sh length With the exception of
sh length these were not investigated further Three variables were routinely
signi cant regardless of whether the sh was kept or discarded vessel shing
scenario and the interaction of vessel with shing scenario Table Depth was
unique in signi cantly in uencing the health of discarded sh but not kept sh
Table
Fish were injured more frequently on Vessel B and Vessel E than on the other
three vessels Table For kept sh this distinction cleanly discriminated these two
vessels from the other three Generally the health and morbidity indices doubled
b etween these two vessel groups For discarded sh the distinctions were less clear
although the rankings were relatively consistent Table In particular Vessel C
consistently returned to the water sh with lower injury frequencies than Vessel B
and this di erence was greater than a factor of two for b oth indices In general the
condition of kept and discarded sh on a given vessel was similar
Fishing scenario exerted a signi cant e ect on the health and morbidity indices
for that shing scenario but in no case did an a posteriori test identify the source of
these signi cant di erences Table Failure to identify the source of signi cance
in the ANCOVA comes from the signi cant interaction b etween vessel and shing
scenario as subsequently discussed Table For discarded sh control sh
consistently ranked higher in health or morbidity index that is these sh were
injured more often and more seriously Table The shing scenario using the
slot limit consistently ranked lowest that is these sh were injured least often
Intermediate and never signi cantly di erent were the reduced minimum size and
cumulative size shing scenarios Table
The interaction term b etween vessel and shing scenario was signi cant in all
cases Table We examined this interaction for discarded sh The origin of
this interaction is twofold For the slot limit trips discards on Vessel B were in
signi cantly p o orer health than the discards on the remaining vessels For the
Draft February
cumulative size scenario discards on Vessel D and Vessel C were in signi cantly
b etter health than the discards on the remaining vessels The latter trend was
distinct from the overall trend in health for discarded sh among vessels Table
whereas the former was consistent with it
Overall the morbidity index diverged signi cantly b etween kept and discarded
sh interaction terms with vessel and shing scenario were also signi cant Tables
and To investigate the latter we restricted the ANOVA and assigned each sh
to a main e ect category of kept or discarded We included the two imp ortant main
e ects identi ed in Table vessel and shing scenario plus all pairwise interaction
terms The health of kept and discarded sh was signi cantly di erent Table
Interestingly the morbidity index averaged higher for kept sh versus for
discarded sh Thus the larger kept sh on average were characterized by more
frequent and severe injuries
As a consequence of the consistent signi cance of the interaction terms relating
vessel to shing scenario we evaluated the morbidity index separately for each
vessel and shing scenario We retained the other main e ect and appropriate
interaction term in each ANCOVA For shing scenario the morbidity index
and the diverged signi cantly for the control legal scenario P
slot limit scenario P and very nearly so for the cumulative size scenario
P For the control scenario the morbidity index was for the
discarded sh and for the kept sh The resp ective values for the cumulative
size scenario were and and for the slot limit scenario and
Thus for the two alternative scenarios the discarded sh were injured much less
frequently than the kept sh This was not true for the controls In contrast to
shing scenario only one vessel recorded a signi cant di erence in the morbidity
index b etween kept and discarded sh Vessel E P Discarded sh were
in signi cantly b etter condition on this vessel than kept sh morbidity indices of
and resp ectively
Depth signi cantly in uenced the health of discarded sh Fish caught in
deep er water were recorded with an increased frequency and severity of injury The
correlation b etween depth and the health of discarded sh though signi cant was
not strong Sp earman s
Draft February
Fish length generated only a single signi cant result for the morbidity index
for discarded sh Table An a posteriori test failed to resolve sp eci c sizes that
diverged signi cantly in morbidity from others however the trends b etween size
classes were interesting Fish averaging highest on the morbidity index were the
smallest sh Table Largest sh and ranked second and
third highest in this injury index Least injured sh were in size classes covering
the range The morbidity index averaged fully one third lower for the least
injured size class relative to the two most injured size classes and
Table
The size of sh discarded dep ended primarily on the vessel and the shing
scenario Table Time of day depth and e ort were never signi cant and only
a few interactions terms returned a weakly signi cant signal Vessel in uenced the
th
largest size of sh discarded The p ercentile of size did not vary signi cantly
th
with vessel whereas the p ercentile and the interquartile range were highly
signi cantly di erent The vessel e ect issued from two sources Vessel B had
th
a higher prop ortion of smaller sh The mean and p ercentile of size were
signi cantly smaller for Vessel B than for the other vessels Table Vessel D and
th
Vessel E caught larger sh than the other vessels The p ercentile of size was
signi cantly larger for these two vessels than for the others Table
Fishing scenario exerted a signi cant e ect on all descriptors of the size
frequency distribution Table The mean and p ercentiles of size were signi cantly
larger for the control scenario than for the others as exp ected Table Each of
the other scenarios allowed the landing of smaller sh The slot limit scenario fell
intermediate b etween the controls and the cumulative size and reduced minimum
size scenario Table This to o was exp ected as the landing of sh b elow legal size
was more constrained by this shing scenario than by the other two exp erimental
alternatives As anticipated the trend towards signi cant variation in the size of
sh landed was emphasized at the upp er end of the size frequency distribution as
th th
exempli ed by the p ercentile The p ercentiles did not di er signi cantly
among the three alternatives Table These sh were to o small to b e
landed using any shing scenario
Draft February
Discussion
ersp ective P
The present day management plan for constraining landings in the summer
ounder recreational shery to a total allowable landing target is based on the
combined implementation of a bag limit and a size limit A sh caught if the
bag limit has not yet b een reached and if of su cient size can b e landed if the
angler so cho oses This implementation of bag and size limits has worked with
decreasing e cacy as the spawning sto ck biomass of summer ounder has reached
historical highs First the fraction of caught sh meeting bag limit and size limit
criteria is low This is particularly true nearshore where summer ounder tend to
average of smaller size This degrades the recreational exp erience Second the
fraction of caught sh meeting bag limit and size limit criteria is low enough that
discard mortality b ecomes an imp ortant comp onent of total shing mortality for
the recreational shery This happ enstance exists despite an assumed fraction of
discards dying that is relatively low
The recreational shery comprises a numb er of angling approaches including
shermen who sh from shore anglers on small often self owned b oats and
anglers participating more communally on party b oats The party b oat shery
for summer ounder is an imp ortant recreational shery in the Mid Atlantic Bight
We examined vessels from two states New York and New Jersey with the intent
of testing the e cacy of mo di cations in bag limit and size limit restrictions
presumably reducing discards without increasing landings As ultimately the
management of this sh is based on biomass Terceiro the fo cus was on the
conversion of discards of biomass to landings of biomass The landing of smaller
sh under a de ned bag limit militates in favor of a decrease in landings biomass
The caveat is of course that a shift to the landing of smaller sized sh would
reduce biomass but increase numb ers of sh removed from the sto ck without careful
mo dulation of the bag limit We did not explicitly evaluate that trade o rather
by observing shing trips on party b oats we gathered data on the likely value of
this trade o Bo chenek et al submitted and estimated further in this study the
in uence on discard mortality by this shift of e ort
Draft February
We compared three p otential shing scenarios to the legal control sce
nario The rst was a slot limit in which a few of the sh were allowed to fall within
a slot b ounded on the lower end by a size restriction b elow legal size in our
case The second was a simple reduction in minimum size without a mo di cation
of the bag limit The nal alternative was the restriction of landings to a cumulative
total size This approach con ates bag limits with size limits since landings are
a function of the cumulative length of sh retained relative to a legally imp osed
cumulative size calculated as the multiple of the legal size and bag limit Bo chenek
et al submitted evaluated the catch and discards of observed trips under each of
the four shing scenarios Here we examine the in uence of these options on the
likely survival of discards
We stress one imp ortant additional caveat The summer ounder recreational
shery has evolved such that the bag limit is nearly non functional to day That
is the restriction on landings is achieved almost entirely by a size limit su ciently
draconian as to restrict the numb er of sh that can b e landed by their abundance
and availability to a very small numb er p er angler p er day As a consequence the
in uence of the three alternative plans is primarily in relaxing this size limitation
allowing the angler to retain a numb er of sh more near the bag limit From the
p ersp ective of the sto ck the result is likely a reduction in the biomass removed
but an increase in the numb er of individuals due to the rapid increase in weight
for a given increment in length However given the limited in uence of the bag
limit the result may well b e an increment in biomass and numb er Consequently
cases where discard reduction minimized discard mortality should not blithely b e
assumed to indicate that a reduction in total shing mortality would b e achieved
thereby if implemented through regulation as a p ortion of the present regulatory
y
scheme is e ectively dysfunctional
raction of Injured Fish The F
We identi ed a series of injuries and building on previous studies e g
Muoneke and Childress Zimmerman and Bo chenek Malcho et al
partitioned them into two primary categories sh that were gut ho oked and
y
W e assume that the primary purp ose of the dysfunctional bag limit is to generate hop e in the optimistic angler
Draft February
sh that were bleeding after ho ok removal or from other injuries o ccurring during
capture The latter in particular covered a range of limited to more serious injuries
This range was encompassed by an observer s judgment as to whether the sh was
generally healthy grading to moribund and the observation that more seriously
injured sh often were b oth bleeding and gut ho oked Of course sh were also
recorded as dead A binomial health index was generated based on the separation
of sh into two categories those without any observable injury b eyond minor ho ok
damage versus those injured in either way or dead
What is surprising is the overall rarity of injured sh The highest rates
observed approximated the assumed frequency of discard mortality used in recent
assessments of summer ounder Terceiro The overall mean for the
study however including the shing scenarios and vessels with the higher rates
was a value ab out half that high Likely many of these injured sh will
not recover but anticipating that even a few of them do the results of this study
suggest that the presently assumed probability of mortality up on discard is high by
at least a factor of two in the party b oat sector of the recreational shery
Discard mortality is usually assumed equivalent across size classes in sto ck
assessments That is the case for summer ounder as an example Terceiro
In this study the injury rate varied considerably across length classes by a factor
of three Malcho et al did not nd length to b e a signi cant predictor
of mortality in recreationally caught summer ounder however that study did
resolve an interaction b etween injuries resulting in bleeding and length In our
study the trend in injury frequency was nonlinear Medium sized sh were injured
less frequently than small and large sh The di erential was a primary mo dulator
of the outcome of the e ect of shing scenario on the p otential for discard mortality
The results of this study suggest that increased accuracy in the estimate of discard
mortality can b e acquired by the use of size dep endent mortality rates
Vessel E ects
Vessels B and E were asso ciated with higher overall injury rates for discarded
sh Vessel B shed inshore in lo cations where small sh were particularly
common Small sh averaged highest in injury rate Table This asso ciation
Draft February
explains the unfortunate p osition of Vessel B in this hierarchy and suggests that
discard mortality rates should not b e considered equivalent over the inshore o shore
gradient of the shery Vessel E supplied a b eak ho ok to anglers not supplying
their own gear This ho ok style di ered from the wide gap or o ctopus ho oks
supplied by the remaining vessels Although uncertain the p ossibility exists that
this ho ok style was resp onsible for the higher injury rates Di ering ho ok styles
have b een asso ciated with di erential mortality rates Bartholomew and Bohnsack
Millard et al
Vessel e ects also mo dulated the size frequency distribution On average
Vessel D and Vessel E shed in relatively deep water o shore whereas Vessel B
shed in shallow estuarine and inshore waters Smaller summer ounder tend to b e
found inshore and in estuaries e g Szedlmayer and Able thus explaining
the vessel e ects observed Vessel B discarded disprop ortionately larger numb ers of
sh in size Vessel D and Vessel E discarded many more sh and larger
Fishing Scenario
The three alternative shing scenarios p ermitted retention of sh smaller than
legal size Not surprisingly the sh discarded on the control trips which to ok place
under legal conditions averaged larger than the alternative scenarios Discards
averaged somewhat smaller for the slot limit scenario and considerably smaller for
the other two alternatives Table The di erential b etween the three alternative
scenarios is explained primarily by the di erential in the numb er of medium sized
sh kept and hence the numb er of medium sized sh discarded Discarding of these
medium sized sh was prop ortionately more frequent with the slot limit scenario
b ecause this scenario limited the retention of sublegal sized sh more than did the
other two alternatives As a consequence the three alternative shing scenarios did
th
not di er signi cantly in the p ercentile of size but signi cant di erences did
th
exist in the p ercentile of the size distribution discarded
Several facts are immediately apparent from the comparison of injury rate
across shing scenario The control or legal scenario yielded the highest
p otential discard mortality rates More injured sh were released in this shing
approach than any other The slot limit scenario and cumulative size scenario
Draft February
consistently generated the lowest p otential discard mortalities and b oth were
consistently signi cantly lower than the control legal scenario Table The
di erence was a factor of two for the cumulative size scenario and an impressive
factor of three for the slot limit scenario Furthermore the comparison of health
b etween kept and discarded sh is increasingly favorable with these alternative
plans Discarded sh are consistently in b etter condition relative to kept sh in
the alternate plans in comparison to the control plan This trend is furthermore
explained by the lower injury frequency for medium sized sh to in size
The control scenario resulted in discarding of larger sh and these sh were
characterized by a higher frequency of injury The alternative scenarios allowed
increased retention of sh to in size and thus fewer more gravely injured sh
were discarded Accordingly the relative health of kept and discarded sh diverged
to a greater degree for the three alternative shing scenarios than observed on the
control trips
the Outcomes Factors Underlying
Corresp ondence analysis provides an holistic view of the dataset that p ermits
ferreting out the interactions most resp onsible for the overall trends previously
discussed Three dimensions explained the distribution of injury states with resp ect
to the descriptive variables de ning the shing trips vessel time of day shing
scenario depth and e ort Dimensions and discriminate the ve shing vessels
based on the depths shed and size classes of sh discarded Figure Note the
asso ciation of Vessel A with the deep est depths Z Vessel C with depths of
ft Z and Vessel B with the shallowest depths Z and the smallest sh L
Several inferences concerning the relationship of the frequency of injured sh
with descriptors of the shing trips can b e derived from a p erusal of Figure First
uninjured sh are p ositioned at the center of the diagram These sh were observed
commonly on all vessels and in all shing scenarios Second Vessel E the control
scenario and sh of sizes ab ove are p ositioned near the sh injured by b eing
gut ho oked or observed gut ho oked and bleeding These characteristics distinguish
the control scenario from the three alternatives Fish simply bleeding are nearer
the diagrams center and so were more distributed amongst all vessels sh sizes
and shing scenarios The control trips were resp onsible for a disprop ortionate
Draft February
numb er of gut ho oked sh as was Vessel E Third dead sh fall near the center
of the diagram Dead sh are relatively evenly distributed among all vessels The
relationship of sh injury frequency with vessel and shing scenario is dominantly a
function of the health of sh released alive Finally Dimension identi es the slot
limit scenario as distinctive in the distance of this scenario from morbidity classes
identifying injured sh
Comparison of the p ositions of trip and health descriptors on axes de ned
by Dimensions and re emphasize most of these previous observations Figure
Dimension clari es the in uence of length class on the remaining primary and
supplementary variables Of particular note is the consistent asso ciation of relatively
large sh those sh that were shown to b e injured more frequently than medium
sized sh with injuries from gut ho oking and with the control regulated
shing scenario Dimension shows that sh simply bleeding are less asso ciated
with this former group of categorical identi ers Once again the slot limit scenario
o ccupies a unique p osition on this diagram well separated from any morbidity or
injury categories identifying injured sh
Dimension separates two of the alternative shing scenarios reduced mini
mum size and cumulative size a feat not accomplished by Dimensions Figure
Dimensions and did not in uence the distribution of health indices and so
are not discussed herein The reduced minimum size scenario is asso ciated more
closely with dead sh than other shing scenarios in this diagram and this as
so ciation explains the somewhat higher morbidity index for this shing scenario
than observed for the other two alternatives relative to the control scenario The
cumulative size scenario o ccupies a unique p osition most closely asso ciated with
medium to small sh Note also in Figure that the two alternative sh
ing scenarios cumulative size and reduced minimum size are not asso ciated with
any vessel As in the previous two gures the slot limit scenario is asso ciated with
Vessel C This suggests that the somewhat b etter p erformance of the slot limit sce
nario may in part b e explained by a uniquely b etter p erformance of this scenario on
Vessel C Vessel C had unusually go o d morbidity indices for discarded sh Table
Of course b oth Vessel C and slot limit trips may have b een uniquely asso ciated
with low injury frequencies and so coincidentally lo cated in corresp ondence space
Draft February
Corresp ondence analysis therefore o ers explanations for a numb er of the
statistical results obtained The control scenario pro duced higher injury frequencies
than other shing scenarios This increased injury frequency was due to the discard
of larger sh that tended to b e gut ho oked The reduced minimum size scenario
had the p o orest morbidity index of any alternative shing scenario due to the
observation of an increased prop ortion of dead sh Whether this is happ enstance
or inherent to this shing approach is not known The shing approach that
p erformed b est the slot limit may not b e a true improvement over the cumulative
size approach as the slot limit may have b ene ted from the unusually go o d
p erformance of Vessel C Uninjured sh were common on all vessels and in all
shing approaches Injury frequency was in fact remarkably low in comparison
to the assumed frequency of mortality among discarded summer ounder in the
recreational shery Terceiro
The study o ers no supp ort for the e cacy of the present day management
system in controlling discard mortality Simply put the present day regulatory plan
maximizes discards Bo chenek et al submitted and at the same time maximizes
the discard of injured sh less likely to survive Any of the alternative plans is
an improvement but the slot limit and cumulative size plans are deserving of the
most scrutiny Both of these scenarios minimize the discard of relatively large sh
to that are more likely to b e gut ho oked and therefore presumably more
likely to die after discard Furthermore p ermitting enhanced retention of smaller
sh prop erly managed would p ermit survival of more large sh As the commercial
shery inherently acts to truncate the size frequency distribution with the degree
of impact mo dulated solely by the landings limits p ermitting increased survival of
the largest size classes recreationally may b e b ene cial in retaining a distributed
size frequency distribution in the sto ck
wledgments Ackno
This study was funded by the Mid Atlantic Fisheries Management Council
Research Set aside Program using the donations of quota from recreational and
commercial sheries We thank the Recreational Fishing Alliance for logistical
supp ort with the party b oat industry and the National Fisheries Institute Scienti c
Monitoring Committee for handling the exempted shery that converted allo cated
Draft February
quota into nancial supp ort for this research program Fish quota was caught
by vessels from Virginia to Massachusetts We appreciate the e orts of the many
shing vessels involved in this endeavor We are particularly appreciative of the ve
captains and their crews that participated in this research program who diligently
collected data on every drift and who supp orted the needs of the scienti c observers
Finally our thanks go to the anglers who participated on these shing trips They
unanimously supp orted the testing of the di erent shing scenarios in every case
fully participating in the endeavor
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Draft February
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recovery Mar Environ Res
Jennings S and Kaiser M J The e ects of shing on marine ecosystems
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Maguire J O Donoghue M Jenkins S Brand A and Burnell G M
Draft February
Temp oral and spatial variability in dredging induced stress in the great scallop
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Draft February
Sci
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Draft February
Table Results of ANCOVA analyses examining the in uence of trip and
catch characteristics on the health injured or uninjured and morbidity indexes
Dep endent and indep endent variables are describ ed in the Metho ds section not
an interaction term signi cant at
Health index Morbidity Index
Fish Discarded Fish Kept Fish Discarded Fish Kept
Signi cance Level Signi cance Level Signi cance Level Signi cance Level
Vessel
Time of day
VesselTime of day
E ort
Fishing Scenario
Depth
Length Class
VesselFishing Scenario
Draft February
Table Results of Tukey s Studentized Range tests for the in uence of vessel on
health injured or uninjured and morbidity indices Similar letters within column
categories indicate vessels not signi cantly di erent at Listed under the
health index category in order are the Tukey ranking ratio of injured to uninjured
sh and the numb er of sh analyzed Listed under the morbidity index category
in order are the Tukey ranking and the morbidity index to p oint scale
Health index Morbidity Index
Fish Discarded Fish Kept Fish Discarded Fish Kept
Vessel Signi cance Level Signi cance Level Signi cance Level Signi cance Level
Vessel A AB AB AB AB
Vessel B A A AB AA AB
Vessel C AB AB AB AB
Vessel D AB AB AB AB
Vessel E AA AB AB AB
Draft February
Table Results of Tukey s Studentized Range tests for the in uence of shing
scenario on health injured or uninjured and morbidity indices Similar letters
within column categories indicate shing scenarios not signi cantly di erent at
Listed under the health index category in order are the Tukey ranking
ratio of injured to uninjured sh and the numb er of sh analyzed Listed under
the morbidity index category in order are the Tukey ranking and the morbidity
index to p oint scale
Morbidity Index Health index
Fish Discarded Fish Kept Fish Discarded Fish Kept
Fishing Scenario Signi cance Level Signi cance Level Signi cance Level Signi cance Level
Control AAA A AAA A
Reduced Minimum Size AB C A ABC A
Cumulative Size ABC A ABC A
Slot Limit CCC A CCC A
Draft February
Table Results of ANOVA analyses examining di erences in the morbidity index
b etween kept and discarded sh an interaction term
Signi cance level
Kept versus discarded
Vessel
Fishing Scenario
VesselFishing Scenario
VesselKept versus discarded
Kept versus discardedFishing Scenario
Draft February
Table Average values of the morbidity index for each of the seven summer
ounder length classes for summer ounder discards only Morbidity is assigned to
a to p oint scale with uninjured sh given a rank and dead sh a rank of
Lowest averages indicate lowest injury rates Fish with lengths equivalent to the
length class b oundary were assigned to the higher length class
Length Class Morbidity Index N
Draft February
Table Results of ANCOVA analyses examining descriptors of the size frequency
distribution of discards not signi cant at an interaction term
th th
Percentile Median Percentile Interquartile Range Mean Size
Vessel
Time of day
Fishing Scenario
Depth
E ort
E ortVessel
DepthVessel
Draft February
Table Results of Tukey s Studentized Range tests for the in uence of vessel
on descriptors of the size frequency distribution of summer ounder discards
Similar letters within column categories indicate vessels not signi cantly di erent
at Listed under the mean size descriptor category in order are the Tukey
ranking the value and the numb er of trips analyzed Listed under the remaining
categories in order are the Tukey ranking and the value
th th
Percentile Median Percentile Interquartile Range Mean Size
Vessel A ABC AA ABC AB AB
CCC AB CCC AB AA Vessel B
Vessel C BBB AA ABC AB AB
Vessel D AAA AA AAA AA AB
AA AA AAA AA AA Vessel E A
Draft February
Table Results of Tukey s Studentized Range tests for the in uence of shing scenario
on descriptors of the size frequency distribution of summer ounder discards Similar letters
within column categories indicate shing scenarios not signi cantly di erent at
Listed under each category in order are the Tukey ranking and the value The numb er of
trips measured is listed in Table
th th
Mean Size Percentile Median Percentile Interquartile Range
Control AAA AA AA AAA AA
Reduced Minimum Size CCC AB AB CCC AB
ABC AB AB CCC AB Cumulative Size
Slot Limit BBB AB AB BBB AB
Draft February
Figure Lo cation of shing trips on each of the ve vessels participating in the study
Plotted are the central p ositions of each drift
-73.5Ê
-76Ê -75Ê -74Ê -73Ê -74Ê 41Ê 41Ê
New York
40.5Ê 40.5Ê Vessel E Vessel D
40.5Ê 40.5Ê Pennsylvania -73.5Ê
-74.5Ê -74Ê 40Ê 40Ê -74Ê -73.75Ê 40.25Ê 40.25Ê Vessel C
New Jersey
Vessel B -75Ê -74.75Ê -74.5Ê
39Ê 39Ê 39Ê 39Ê
40Ê 40Ê Delaware -74.5Ê
Vessel A
-76Ê -75Ê 38.75Ê -74Ê -73Ê 38.75Ê
-74Ê -73.75Ê
-75Ê -74.75Ê -74.5Ê
Draft February
Figure Results of corresp ondence analysis for the rst two axes Dimensions and The
primary variables used were categorical variables describing the characteristics of the shing
trip vessel time of day shing scenario length class and the categorical variables for e ort
and depth Supplementary variables p ositioned on the axes de ned by the primary variables
included the morbidity index the injury index and the health index Category abbreviations
are de ned in the Metho ds section
Draft February
Figure Results of corresp ondence analysis for the rst and third axes Dimensions and
The primary variables used were categorical variables describing the characteristics of the
shing trip vessel time of day shing scenario length class and the categorical variables
for e ort and depth Supplementary variables p ositioned on the axes de ned by the primary
variables included the morbidity index the injury index and the health index Category abbreviations are de ned in the Metho ds section
3 [
[ L12
2 [
[ DECD HIGH V-I
1 [ V-IV BLED L13 [ CMSZ Z80 Z20 SLOT L14 RMSZ ILL MHGH AM GOOD[ 0 V-V MLOW WELL SICK Z40 PM DEAD GUT MORB L15 BGUT [ LOW Dimension 3 L16 Z60 V-III CNTL V-II -1 [ L17
[
-2 [ L18
[
-3 [ -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 Dimension 1
Draft February
Figure Results of corresp ondence analysis for the rst and sixth axes Dimensions and
Dimensions and did not explain variation p ertinent to the supplementary variables
and are not gured The primary variables used were categorical variables describing the
characteristics of the shing trip vessel time of day shing scenario length class and the
categorical variables for e ort and depth Supplementary variables p ositioned on the axes
de ned by the primary variables included the morbidity index the injury index and the
health index Category abbreviations are de ned in the Metho ds section
[
[
2 [
1.5 [
CMSZ
1 [ L13 HIGH LOW
0.5 [ PM V-IV Z60 Z20 V-III L14 [ L18 0 MHGH NWELWELL BLED GUT V-V GOOD CNTL MORB Z40 ILL Z80 SICK V-I SLOT L15 V-II BGUT L16
Dimension 6 L17 DEAD -0.5 [ AM MLOW DECD
[ -1 RMSZ
L12
-1.5 [
-2 [ -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 Dimension 1
[
[