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Discussion Starter · #1 ·
SBTC Report #2004-4
A report prepared by the
Striped Bass Technical Committee
for the Atlantic Striped Bass Management Board
November 2004

2004 Atlantic Striped Bass Advisory Report

State of the Stock

Stock Size: The estimate of total abundance for January 1, 2004 is 56.7 million age-1 and older
fish due to the strong 2003 year-class. This estimate is about 11 million fish higher than the
average stock size for the previous five years and 23.8% higher than the 2003 abundance.

Spawning Stock Biomass (SSB): The female spawning stock biomass for 2003 is estimated at 30
million pounds which is above the recommended biomass threshold of 28 millions pounds (12,726
mt). However, most TC members expressed concern over the current estimates spawning stock
biomass and, hence, the conclusions derived from these estimates.

Recruitment: Recruitment of the 2003 cohort for all stocks combined is 21.6 million age-1 fish
and is the highest observed in the time series. Preliminary survey indices for young-of-the-year
striped bass for 2004 in Chesapeake Bay indicate that the 2004 year-class is of average strength.
Fishing Mortality Rates: Based on VPA results, average age 8-11 fishing mortality in 2003 is
estimated at F=0.62 (a 77% increase compared to 2002) and exceeds the Amendment 6 target of
0.30, and above the threshold of 0.41. However, all technical committee members expressed
concern over the terminal year estimate of F from the VPA and, hence, the conclusions derived
from this estimate.

Based on spawning area tagging programs, stock-specific, model-based estimates of fishing
mortality in 2003, for fish greater than twenty-eight inches total length, were 0.40 for the Maryland portion of the Chesapeake Bay; 0.28 for the Rappahannock River; 0.28 for the Delaware
River, and 0.09 for the Hudson River. Based on coastal tagging programs, fishing mortality
estimates ranged from 0.09 for MA to 0.24 for the New York Ocean Haul Seine. The tag-based F
estimates were not similar to the F (N-weighted) estimates (F in 2003 = 0.53) produced in the
VPA and did not show an increase in F for 2004 (except for Maryland).

Chesapeake Bay fishing mortality in 2003 is estimated at F=0.20 by the direct enumeration study. This F represents mortality during the June 2002 ? June 2003 period, so it is not directly
comparable to the average, weighted (by N) VPA calendar-year F on age 3-8 striped bass equal to
0.18.

Exploitation Rates: Based on the tagging programs, R/M estimates produced by 3 (New York
Ocean Haul Seine, Delaware River, Maryland/Chesapeake Bay) out of 8 programs were generally similar in magnitude to the exploitation rates derived using F estimates from the current ADAPT assessment for years 1990-1999. However since 2000, the R/M estimates have declined, indicating exploitation has decreased.

Catch: Total catch in numbers including landings and discards increased from 3.7 million fish
in 2002 to 4.7 million fish in 2003, a 26.3 % rise losses. The 2003 catch was above the 1996-
2003 average of 4.0 million. Ages 3 to 7 represented 64%, and ages 8+ represented 30% of the total catch in 2003. The 1998 and 1996 year-classes dominated the catch, accounting for 29% of total catch. Total catch of age 8+ fish increased from 926 thousand fish in 2002 to 1.4 million fish in 2003 (the highest level recorded in the time series) and the proportion of 8+ fish in the catch increased to 30% in 2003 from 25% in 2002.

Recreational harvest (2.4 million fish) and discards (1.2 million fish) accounted for 76% of the total 2003 catch. Maryland recreational fisheries harvested 21.8% of total recreational landings, followed by MA (16.9%), VA (16.7%), NJ (16.3%), and NY (13%). The remaining states each
landed 5% or less of the total recreational landings.

Commercial harvest (0.86 million fish) and discards (0.27 million fish) accounted for 24% of the total 2003 catch. Maryland commercial fisheries harvested 50.8% of the total commercial
landings, followed by VA (18.7%), PRFC (9.6%), NY (7.9%), and MA (6.4%). The remaining states each landed 4% or less of the total commercial landings.

Data and Uncertainty: No new data sources are included in this year's assessment. Tuning
indices are similar to those used in past years, with some minor adjustments to the age-specific
indices (Maryland SSN, Massachusetts, and NEFSC).

The Technical Committee expressed great concern over the divergent patterns in F observed
among the VPA and tag-based programs and believes that both methods need to be further
scrutinized to reconcile the differences. Violation of the model assumptions is the primary
reason believed to have created the model differences, and these are discussed below.

Some members of the Technical Committee were concerned that the VPA is not adequately
robust when dealing with a mixed stock such as coastal striped bass. In addition, the survey
indices used in the tuning process of the VPA may not be providing accurate trend estimates for
older fish due to the surveys? abilities to track the striped bass abundance as the population
abundance has potentially plateaued in recent years. Some members of the Technical Committee
were concerned that the distribution of larger striped bass may have shifted to offshore waters as the population has increased in abundance. Since the EEZ is closed to harvest and there is
limited fishery independent survey data for older striped bass beyond state waters, these fish may
not be fully represented in the assessment. However, other TC members suggest this may not be
an issue since MD and VA spawning ground surveys provide relative abundance data on these
larger fish when they have migrated from the EEZ to the spawning grounds in the spring. Other
methods that are capable of directly accounting for mixed stock management units should be
explored in the future and self-evaluation of surveys by each state should be performed,
following recommendation made by the VPA indices workshop.

Other members expressed concern that there is considerable error in the catch produced by the
MRFSS survey in 2003. Some states did not believe that the increased harvest in some waves
was real because the trend contradicted independent observations on fishing effort (hurricanes interrupted angling in 2003) and angler opinions. However, some states could account for the increases in harvest. Other members expressed concern that the estimates of harvest are underestimates because the winter fisheries in North Carolina and Virginia are not being taken into account. It is recommended by the TC that, at least, MRFSS survey in NC should be
expanded into wave 1 to account for winter fisheries? harvest. Due to error in MRFSS catch
estimates, the TC also recommends that some statistical catch-at-age models that be explored
that could incorporate error and tagging information.

Some members were also concerned that the tag based estimates of survival among coastal
programs were so variable and that the estimates changed considerably depending on the year
reported. It is possible that the assumption of mixing and dispersal is not being adequately met
to provide a comprehensive estimate of mortality. If such assumptions are violated, the estimates
could change in trend and magnitude. Others questioned whether the reporting rate derived by
DE and used by all states is accurate. Since reporting rate is an important variable used in
tagging model and R/M estimates, the TC recommends that a high-reward, coast-wide tagging study be conducted in the future. In addition, more analyses to examine the violation of assumption in the tagging models should be conducted.

Some Technical Committee members believed it is time to notify the Board that there appears to
be a problem with increasing natural mortality in Chesapeake Bay. Des Kahn, Vic Crecco, and
John Hoenig presented analyses that showed an increase in natural mortality on younger
individuals, which is concurrent with the incidence of mycobacterial disease. Several members agreed that the TC should tell the Board that there is some statistical evidence for an increase, but that not all empirical data (e.g., landings in Chesapeake Bay have increased despite supposed rise in M) supports the results of the model estimates. The TC could not resolve any plan of attack to address this issue, but recommends that it be further addressed over the next few
months via email discussions.

Management Advice

Most striped bass technical committee members expressed concern over the current terminal
estimates of F and spawning stock biomass from the VPA and, hence, the conclusions derived
from these estimates. Most members agreed that the landings increased in 2003 compared to
2002 (some states liberalized regulations), and fishing mortality has probably increased
compared to 2002, but they are skeptical that the F estimate from the VPA doubled. Since the
2003 F is a terminal year estimate and it has the highest error, most members believe that the F
estimate produced by the ADAPT model will likely decrease when the stock assessment is
updated in 2005, given the current retrospective pattern. Based on the ADAPT VPA estimates,
the technical committee cannot say with certainty that overfishing is not occurring and that the
population is not overfished. However, since harvest increased compared to 2002, and the
F estimates have been over the target since 1997, there is certainty that the target is still being
exceeded. Until the uncertainties and divergences between the VPA and tag-based models are
more fully investigated, the technical committee recommends that no liberalization of regulations
occur at this time.
 

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"the technical committee cannot say with certainty that overfishing is not occurring and that the
population is not overfished."

They'd like to say it's overfished and cut us even more though wouldn't they. Damned elitist fish managers :D

[ 11-15-2004, 06:01 PM: Message edited by: CaptG ]
 

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and,

fishing mortality has probably increased
compared to 2002, but they are skeptical that the F estimate from the VPA doubled
 

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Discussion Starter · #4 ·
Originally posted by CaptG:
"the technical committee cannot say with certainty that overfishing is not occurring and that the
population is not overfished."

They'd like to say it's overfished and cut us even more though wouldn't they. Damned elitist fish managers :D
Huh? They're doing everything they can not to cut us back even in the face of evidence that we should.
 

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As I read that report, the thing foremost in my mind was the 30 million lbs of weakfish spawning biomass supposedly out there swimming around. Also based on that glorious VPA model.
 

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According to how i read it your rite Bob.

I'd still love to know exactly how the numbers are achieved and to what degree of accuracy, although trends would still be seen even with skewed numbers.
 

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All I'm reading is one uncertainty after another with two counting studies that contradict each other. In all, looks to me like more fish are being replaced than are being taken especially since they aren't even counting the bass in the EEZ or are the studies based on the whole migratory range of the bass.

Looks like the concern for the mortatlity of Big Bass is based only on a VPA estimate that decidedly could be very flawed data.

Tough to base any decisions on this data other than to conclude that they can't possibly cut us when overall abundance is greater than ever.
 

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Discussion Starter · #8 ·
CaptG, re-read.

TwinD's, does it scare you that the only positive sign in the report is the VPA showing an ever increasing stock size. Especially since most biologist feel the population maxed out a few years ago. The only other positive sign is the return rates of the tagging studies. To me it makes little sense to estimate mortality rates based on return rates of tagging studies. They don't come close to tagging enough fish to make that reliable.
 
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