Conservation Management Plan for

Summer Flounder (Paralichthys dentatus)

Ashley Sidhu

Wildlife Ecology & Conservation 11:216:464

December 2, 2015

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Table of Contents

List of Tables and Figures……………………………………………………………………………………..…….. 2

Executive Summary…………………………………………………………………………………………………….. 3

PART I. INTRODUCTION………………………………………………………………………………………………..4

Species Description & Taxonomy………………………………...…………………………………….… 4

Life History & Ecology……………………………………………………………………………………...…. 5

Population Status & Distribution………………………………………………………….……………. 10

Threats & Reasons for Management……………………………………………………………………11

PART II. CURRENT CONSERVATION/MANAGEMENT……………………………………….…………12

Population Monitoring……………………………………………………………………………………….12

Regulatory Protection…………………………………..…………………..………………………………..12

Habitat Conservation……………………………………………………………………………………..…..15

Population Viability Analysis………………………………………………………………………………15

PART III. CONSERVATION AND MANAGEMENT PLAN……………..………………………………….16

Recovery Objective……………………………………………………………………………….......………..16

Population Projection Model………………………………………………………………………………17

Conservation & Management Strategy…………………………………………………..…………….21

Public Outreach and Education…………………………………………………………………….……..24

Further Research & Summary……………………………….……………………………………………24

REFERENCES …………………………………………………………………...………………………………………….26

APPENDICES……………………………………………………………………………………………………………….28

Appendix A: Summer flounder life table…………………………………………………………..….28

Appendix B: Summary of population numbers from survey trawls……………………....29

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List of Figures and Tables

Figure 1: An example of Summer Flounder camouflaging into the seafloor………………………..4

Figure 2: Osprey holding a summer flounder……………………………………………………………………4

Table 1: Life stage duration from eggs to adults……………………………………………………………….5

Figure 3: Eye migration from post-larval stage into adulthood………………………………………….6

Figure 4: Summer flounder geographic range and most abundant areas………………………...…7

Figure 5: Summer Flounder life cycle habitat areas……………………………………………………….....7

Figure 6: Map of northeastern ecological production units…………………………………...…………..8

Figure 7: Prey example - Bay anchovy and blue crab ……………………………………………..……….10

Table 2: Recreational measures for summer flounder, scup, and black sea bass………………13

Table 3: Conservation equivalency for summer flounder recreational management………...13

Figure 8: Population viability analysis……………………………………………………………………………16

Figure 9: Stochastic age-structure matrix model………………………………………………………….…17

Figure 10: Stable Stage Distribution………………………………………………………………………………18

Table 4: Sensitivity matrix for summer flounder…………………………………………………………….19

Table 5: Elasticity matrix for summer flounder………………………………………………………………19

Figure 11: Elasticity values for the survival values for each stage class………………………...….20

Figure 12: Comparative analysis of fecundity and survival estimates from elasticity…….....21

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EXECUTIVE SUMMARY

Paralichthys dentatus, commonly known as summer flounder, are one of the largest and

most commercially successful fisheries on the US eastern coast. Since 1989, summer

flounder populations have undergone critical management steps to drastically increase the

crashing population. As of 2014, summer flounder are considered more stable and not

overfished, but do experience overfishing mainly in the recreational fishing sector.

Management goals from the Atlantic States Marine Fisheries Commission (ASMFC) have set

a Spawning Stock Biomass (SSB) threshold goal of 138 million pounds of summer flounder

to be considered fully sustainable. 2014 data reflects a current SSB of around 90 million

pounds. Efforts are in affect to closely monitor population numbers to ensure the stability

of summer flounder populations. The ASMFC sets yearly fishery allowances and regulations

to maintain and improve the population health. Each year, a 40-60 split of summer

flounder catch is divided between the recreational and commercial fisheries, respectively.

However, with the lack of proper data collection on behalf of the recreational fishing sector,

of which include population size, age, discards, and bycatch, are lacking and have the

potential to completely change the predicted population sizes. Data results for the summer

flounder management plan show that there is a very small positive growth in population

size occurring, assuming that all the provided data is accurate. In addition, sensitivity

models show that the juvenile age class of summer flounder are most sensitive to changes

in fertility and influence changes in population growth (λ) the most. Elasticity models show

that both juveniles and the grouped Adult V stages are most influential for changing λ.

Therefore, conservation efforts need to be directed to protecting the health of juveniles and

their habitat areas, and more research into summer flounder 7 years and older need to be

conducted to explain their influence on population sizes. In addition to regulations set out

by the Mid-Atlantic Fisheries Council, larger population growth can be achieved for

summer flounder through sterner recreational fishery regulation enforcement, more

accurate and thorough data collection, and nurseries habitat health needs to be maintained.

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Figure 1: An example of Summer Flounder camouflaging into the seafloor

PART I. INTRODUCTION

SPECIES DESCRIPTION & TAXONOMY

Paralichthys dentatus is commonly known as summer flounder. It belongs to the ray-finned

fishes class Actinopterygii, flatfish order Pleuronectiformes, and the sand flounder/large-

tooth flounder family, Paralichthyidae. Other common names for summer flounder include

fluke, northern flounder, plaice, and brail. Flounders are distinguished based on their eye

location: left-eyed, right-eyed, and soled. Summer flounder are a left-eyed flatfish in

adulthood but have bilateral eyes in pre-adulthood.

Summer flounder are considered one of the largest and most commercially successful fish

in the Atlantic coast. They are left-sided flatfish, have narrow bodies, and large mouths with

16-28 canine teeth. The pelvic fins are symmetric and considerably separated from the long

anal fin, and the caudal fin has a rounded margin. Late juveniles and adults have their eyes

on the left side and they swim on their side, but larvae begin life with bilateral eyes and

swim straight. The coloration in P. dentatus is the most variable in the flatfish group due to

their ability to camouflage and their ability to adapt to the coloration of the sea (Figure 1).

The chromatophore pigments on their eyed side allow for quick and efficient blending into

the seafloor. Camouflage is critical for summer flounder hunting and protection from

predators (Figure 2). Along the eyed side are several eyespots that change color to assist

with camouflage.

Figure 2: Osprey holding a summer flounder

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In addition to color, the common characteristic of all P. dentatus is that they are white on

the blind side and colored on the eyed side. Some incidences of ambicoloration have

occurred but that has been attributed to incomplete eye migration and a hooked dorsal fin.

Various size estimates have been recorded but it is agreed upon that females are much

larger than males. Morse stated that females have a maximum age and length of 20 years

and 37 inches, respectively, in comparison to males with 7 years and 23 inches. Both are

the more extreme cases, but summer flounder are usually caught or killed by natural

causes before reaching the maximum recorded age. Weight of summer flounder is directly

dependent on sex, age, and length. Older females weigh on average 10-15 pounds. In

contrast, older males on average weigh 2-5 pounds.

LIFE HISTORY & ECOLOGY

Reproduction & Development:

Summer flounder spend their time in both bays and estuaries or in open water near the

continental shelf, depending on their present life stage. The life stage breakdown is

simplified in Table 1 and explains the definition of each stage.

Table 1: Life stage duration from eggs to adults

Life Stage Duration of Stage Notes

Egg 3-6 days Considered <0 years

Larva Years 0-1 ----

Juveniles Years 1-3 Undergoing metamorphosis

Adults Years 3+ Have reached sexual maturity

Summer flounder reach sexual maturity at around three years old. After reaching full

maturity, females will release around 400,000 eggs their first year of maturity. Adults >7

years old can release up to 4,000,000 eggs. The fecundity is dependent on both size and

weight of the female. See Appendix A for the summer flounder life table, which includes

average fecundity rates for each stage class. Once peak gonad development is reached,

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summer flounder begin a spawning migration. Starting in October when water

temperatures are getting cooler, adults will begin to migrate to the Atlantic continental

shelf. They will reach winter breeding grounds in the 50-150m ocean depths. From October

to March, summer flounder will be releasing eggs and sperm throughout the entire

spawning season. The method of releasing eggs over long period of time is known as serial

spawning. Serial spawning is known to reduce fertilized egg death due to the absence of a

single natural event that could destroy fertilized eggs and larva. In order to fertilize the

large quantity of eggs, male and female summer flounder will broadcast spawn into the

open water column. Spawning in such a way increases the probability of fertilization and

protects the eggs from predators on the seafloor. Due to large egg quantities, parental care

is non-existent for the offspring in summer flounder.

After 3-6 days, the eggs hatch into larvae. Once the eggs hatch, larva will be pushed by tidal

currents inshore and spend the next 2-3 years in protective bays and estuaries. From

larvae to adulthood, P. dentatus undergoes metamorphosis. Larvae and adults are very

different for two reasons: adults have same-sided eyes but larva have one on each side, and

adults swim and lie on their side at the bottom of the ocean but larva swim straight and

closer to the top. In a one year period, from larva to juvenile, the right eye will migrate up

and around the head to the left side (Figure 3). During this period, the mouth will not move,

but will develop sharp teeth. From juvenile to adult, summer flounder will increase in size

and the dorsal fins will become more pronounced. With overall age, the length and weight

of the flounder will increase.

Figure 3: Eye migration from post-larval stage into adulthood

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Habitat:

Summer flounder can be found in a large geographic range from Nova Scotia to Florida.

Figure 4 shows the geographic range and the most abundant areas, which are between

Cape Cod, MA and Cape Fear, NC.

Figure 4: Summer flounder geographic range and most abundant areas

Figure 5 illustrates the complexities of the summer flounder life cycle. Depending on the life stage

and time of the year, summer flounder can be found in different areas.

Figure 5: Summer Flounder life cycle habitat areas

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Habitat for summer flounder depends on the life stage. Larvae are found in the pelagic

zone, in contrast to adults in the benthic zone, due to low predator pressures and large food

supplies. Spawning occurs in 50-150m depth water near the Atlantic continental shelf (red

dashed lines in Figure 3), so eggs and larva start in the open water. The water

temperatures are warmer offshore during the winter seasons, which is ideal for proper

spawning conditions and survival for eggs and larva. Throughout the larval phase and into

juveniles, larva will drift via tidal currents inshore and settle in protective coastal and

estuarine nursery areas (i.e. eelgrass beds) in the winter season.

Juveniles are in a transitional phase where they can be found in both the benthic and

pelagic zones. Once they reach sexual maturity and become adults, they will spend the

majority of their life along the sea floor. Since young juveniles are not fully sexually mature,

they do not migrate to the Atlantic continental shelf every fall-winter season. Therefore,

they spend most of their time in bays and shallow, inshore areas while they develop.

Adults prefer sandy habitats, marsh creeks, seagrass beds, and sand flats in deep channels,

ridges, and estuaries during the spring and summer seasons. During the winter seasons,

they live near the continental shelf and will hunt along the seafloors. Seafloors with loose

substrate, such as sand, are ideal for burying their bodies for hunting and protection from

predators, although they will bury their body in gravel and mud.

Figure 6: Map of the Northeast continental shelf of the United States, showing the ecological production units. The core of each EPU is bounded by white, and the nearshore and shelf break special considerations areas are to the west or east of the

core areas, respectively.

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Although the previous habitat migration areas are specific to summer flounder within the

Mid-Atlantic Bight (MAB), all adult summer flounder will migrate to warmer, deeper

waters starting in October until March. Figure 6 shows the bight boundaries along the

northeastern coasts. The New Jersey area exclusively handles summer flounder

populations in the MAB. It should be noted that the Atlantic continental shelf winter

breeding grounds are not exclusively for all summer flounder populations.

Migration:

Starting in October when temperatures are getting cooler, adults will begin to migrate to

the Atlantic continental shelf where water temperatures are warmer. They winter

migration will last until March. Migration begins once peak gonadal development has been

reached and they need to move out to deeper waters to spawn. The oldest individuals will

begin to migrate first, followed by the younger sexually mature adults. It is believed to be

due to older adults having to release more eggs during the spawning period, therefore

needing more time to release their eggs. The migration is meant to provide a warmer

location for proper egg and larval health during the spawning period.

After the cooler season is over and spawning has completed, adults will migrate back

inshore for spring and summer. Following the migration, a northward drift is exhibited

whereby fish return to more northern estuaries in successive years. This results in a higher

occurrence of larger, older fish in the more northern parts of its range. The drift affects

both adults and larva. Larvae primarily depend on a natural tidal current to push them

inshore from the deep oceanic waters.

Diet:

The diet of P. dentatus is mainly carnivorous. They are active predator’s primarily

consuming bony fish and some benthic invertebrates. Due to summer flounders need to

visually seek out prey, they primarily hunt in the daytime. Juveniles tend to consume small

shrimp and crustaceans. Adults tend to consume a variety of fish and invertebrates.

Examples of common prey include small winter flounder, Atlantic silversides, bay anchovy,

blue crabs, squid, and mollusks. Figure 7 shows common prey for summer flounder in the

New Jersey region.

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As lay-and-wait predators, juvenile and adult summer flounders lay on the seafloor, buried

under sand or mud, and then leap or chase after prey. It has been reported that the adults

are distinguishably more active than sluggish, inshore flatfish based on the adult behavior

of chasing schools of small fish to the surface and then leaping out of the water to pursue

them. However, feeding is different for larvae. Larvae are pelagic, therefore will consume

phytoplankton until they advance the juvenile stage. Due to the large amount of eggs, thus

larvae, hatched each season, a large food supply is needed. Since phytoplankton is

abundant, they serve as the ideal food source for summer flounder larvae.

Figure 7: Examples of summer flounder prey – bay anchovy (left) and blue crab (right)

No studies have shown that summer flounder feedings have a significant effect of the

organisms that they consume. It can therefore be assumed that the population of summer

flounder is not too overwhelming to create critical population declines in prey.

POPULATION STATUS & DISTRIBUTION

Abundance and Current Status:

Population abundances for summer flounder are calculated through regional agencies. The

Northeast Oceanic and Atmospheric Administration analyze data from agencies across all

regions to compile a total population report. Appendix B shows the population data table

used to create a cohort life table for summer flounder. Starting from year 2005, age 0 is

32,260,000 individuals, age 1 is 24,681,000 individuals, and so on until age 7+ is 3,855,000.

An issue in the analytical models was that the final age class was grouped together. The

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grouping can lead to inaccurate egg counts and average weights. From the population data,

models to assess future population projections, sensitives, elasticities, and growth rates

were calculated.

THREATS & REASONS FOR MANAGEMENT

Threats towards summer flounder populations are limited. The greatest threat to attain a

stable summer flounder population is inaccurate data models. As explained, low quality

and quantity can misrepresent current population estimates, sex ratios, age distributions,

and sexual maturity information. Although NOAA currently identifies summer flounder to

be a stable population, inaccurate data can discount that statement.

Low Recruitment:

A non-data related threat to proper management is the low recruitment identified in recent

years. Recruitment is the term for when an individual reaches the point of sexual maturity

and can produce individuals for the population. Studies have shown that summer flounder

recruitment figures have been low for the past 5 years. Few studies are looking into why

recruitment is lower, but no conclusive statements can be made. Assumptions are that the

present El Nino is creating adverse temperature fluctuations for younger stages. In

addition, possibly habitat regions with high pollution can be increasing the mortality of

individuals. A decrease in recruitment will begin to reflect lower population values in the

total population since individuals will move to the next age class, therefore won’t reach the

point of sexual maturity, and cannot reproduce. Future data will show a decline in pre-

adult stages for summer flounder populations.

Prized Catch:

Summer flounder are considered a prize fish for commercial and recreational fishermen.

Anglers particularly like the aggressive behavior, heavy weight and longer length of older

adults. Targeting the larger adults can create an age bias and will adversely affect the larva

populations. Since larger adults produce more eggs, hunting only large adults can

significantly decrease the total egg and larva populations.

Bycatch in Squid Fishery:

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Massachusetts squid trawl fisheries has reported large bycatch rates of summer flounder,

in addition to winter flounder, scup, and butterfish. Bycatch is discarded, with large

mortality rates associated with it. They state that 30% by weight of their total catch is

discarded at sea. Data has shown that mainly undersized flounder and scup are being

caught. The study therefore states that pre-adults are being negatively affected by other

fisheries. Research is looking into separator trawl test-trials to separate squid from bycatch

through simple gear modifications.

PART II. CURRENT CONSERVATION/MANAGEMENT

POPULATION MONITORING

Official population estimates are recorded through trawling surveys conducted through

regional agencies, in part with National Oceanic and Atmospheric Administration (NOAA).

New Jersey trawls have been conducted through the New Jersey Division of Fish and

Wildlife (NJDFW) since 1988. Indices of abundance for summer flounder are compiled from

data collected from April to October. By compiling survey trawl data from a variety of data

collection agencies, data bias and inconsistency prove to be a problem with proper summer

flounder data.

REGULATORY PROTECTION

The Mid-Atlantic Fisheries Council develops an annual report to discuss current and future

recreational regulatory applications collectively for summer flounder, scup and black sea

bass. As of 2014, summer flounder are regulated under ‘conservation equivalency’, where

the National Marine Fisheries Service (NMFS) waives federal recreational measures that

would otherwise apply to the exclusive economic zone (3 to 200 miles at sea). The

conservation equivalency is where individual states or regions recommend to the NMFS

measures that are the conservation equivalent of a set of non-preferred coast wide

measures. This requires federally permitted fishing vessels to adhere to the recreational

fishing measures implemented by the state in which they land. For the 2015 year, the NMFS

decided to continue the use of the conservation equivalency and proposed no changes to

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the current management strategy. Due to summer flounder landings being 7.33 million lb.,

the 2015 recreational harvest limit is nearly unchanged at 7.38 million lb. In addition, from

2014 to 2015, no changes in catch and landings limits or commercial changes occurred.

Table 2 shows the management strategy for the 2014 and 2015 recreational years.

Table 2: Recreational measures for summer flounder, scup, and black sea bass, 2014 and 2015 (proposed and currently applied)

Through the conservation equivalency approach, the NMFS Commission uses a regional

approach, which allows regional measures to be submitted. Table 3 includes a breakdown

of states and regions with similar measures. However, within each region, the Commission

requires measures to be identical for minimum size, possession limit, and season length.

Table 3: Conservation equivalency for summer flounder recreation management measures by state, 2014

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The regulations put in place for summer flounder are very different from many other

fisheries. The Commission states that the recreational conservation equivalency approach

has been instrumental in preventing limit sizes from being exceeded. Since the catch and

size limits are set at regional levels, habitat and ecological protection is protected through

each region. Allowing conservation and harvesting to occur more locally, rather than

broadly through the NMFS, has resulted in neutral impacts occurring. The neutral impact

may be due to lack of habitat assessments from each region. Overall, the NMFS does not

foresee drastic changes to recreational regulatory efforts due to adherence to limits,

conservation efforts, and sustainability of summer flounder.

Compliance with applicable laws implemented for summer flounder, scup, and sea bass are

defined within the fishery management plan (FMP). Some of the following regulatory laws

and conventions are as follows:

Magnuson-Stevens Fishery Conservation and Management Act (MSA): requires that

FMPs contain conservation and management measures that are consistent with the ten

National Standards. The most recent FMP amendments address how to implement

conservation and management efforts to prevent overfishing, while achieving on a

continuous basis, the optimum yield for summer flounder.

Information Quality Act (IQA): information should be presented in a comprehensive

manor to the intended users (the affected public) by presenting a clear description of the

purpose and need of the proposed action, the measures proposed, and the impacts of those

measures. It provides a cohesive document that allows non-lawmakers to assess

information and goals of fisheries.

Regulatory Impact Review (RIR): NMFS requires the preparation of an RIR in order to

provide a comprehensive review of the changes in net economic benefits to society

associated with proposed regulatory actions, as well as review any problems and policy

objectives. Doing so addresses economic and sustainable population analysis efforts in

order to ensure the protection of the species and financial aspects.

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HABITAT CONSERVATION

The conservation equivalency regulations in place through NOAA that allows summer

flounder populations to be regulated at a regional level. Habitat conservation efforts are

localized by the regional agencies that set limits for their fishery, which may allow for

better habitat conservation efforts.

From the New Jersey perspective, the ASFMC recognizes the shoal waters of Cape Cod Bay

and estuaries, bays, and harbors of Cape Cod are critically important juvenile flounder

habitat. The American Littoral Society and New Jersey’s NOAA branch are two larger

associations that analyze summer flounder habitat areas.

POPULATION VIABILITY ANALYSIS

A population viability analysis was conducted to project the population of summer

flounder after 50 years through 100 trials. N0 was determined from total population table

in Appendix B. Mean λ was calculated from the average of 𝑁𝑥+1

𝑁𝑥 for each stage, starting at the

larvae stage. The egg stage could not be used because the value was so large that it

adversely affected the other stage calculations. Mean λ equals 3.7112. The standard

deviation of lambda (σ) is 0.5 and was chosen arbitrarily. Other σ values were tested on the

N0 and mean λ to see the effect it had on population extinctions. σ’s between 0 and 1

resulted in an extinction rate of 0, but 1.2-2 resulted in a rapid increase in the probability of

extinction. Figure 8 shows the results of the population viability analysis. The population

shows an increase in the population size over 50 years for all trials. It can be concluded that

summer flounder populations are currently increasing based solely on the population

assessments from 2005 to 2012. In order to fully assure a positive population growth, a

stochasticity model, as shown in Part III, takes into account fecundity and survival is

necessary.

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Figure 8: Population viability analysis (PVA) of summer flounder population in the semi-log scale. N0 = 32260000 based on total population from Appendix A life table. Trend shows an increase in number of individuals over a 50 year period. 0 extinctions occurred and all trials persisted.

PART III. CONSERVATION AND MANAGEMENT PLAN

RECORVERY OBJECTIVE

As of 2015, summer flounder populations are considered to be in good condition.

Projections show an annual increase in populations based on the NOAA data. In order to

improve the population, goals need to be set to improve the overall data collection process,

develop better age and sex determination methods, protect sensitive age classes, and

educate recreational fisherman on proper handling. Fisheries have changes to seasonal

limits and provisions; therefore, no scheduled plan is assigned to improve the population.

Most of the conservation efforts will be performed through government agencies and

organizations in order to localize efforts. Efforts should be focused towards reaching the

2015 Summer Flounder Spawning Stock Biomass (SSB) target weight. Doing so would be

directly correlated to seeing an increase in population values. It should be noted that

protecting the sexually immature stage classes (i.e. larva and juveniles) needs to also be

1

1000

1000000

1E+09

1E+12

1E+15

1E+18

1E+21

1E+24

1E+27

1E+30

1E+33

1E+36

0 5 10 15 20 25 30 35 40 45 50

Nu

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of

Ind

ivid

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ls

Year

Projection of 100 Population Simulations in 50 Years: Semi-Log Scale Mean λ = 3.7113 and Std = 0.5

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done because SSB does not include stages that don’t reproduce. Since the SSB graphs are

the primary figures that explain summer flounder populations, a separate figure needs to

be created to explain pre-adult populations. Excluding the non-reproducing stages from

population models can invalidate proper population estimates.

POPULATION PROJECTION MODEL

Age-Structured Stochastic Model:

Population models are best represented with stochastic elements are included in the

model. Fertility and survivorship values for each stage class are factored into the growth

rate (λt). Fertility and total population values were factored into population growth which

allows a better representation of a living fishery model. Figure 9 shows the population

growth of summer flounder when including age-structure and fertility. The graph shows a

clear increase in population over a 25 year span. At 25 years, λ converged at 1.14

suggesting a 14% increase in population at each time step (year). The summer flounder

population in question is therefore in positive growth. An increase in population is

consistent with summer flounder studies stating the population is in good condition.

Figure 9: Stochastic age-structured matrix model for summer flounder population. λ = 1.14 converged at 25 years. Median total population after 25 years is examined. Results determined by total population, fertility and survival probabilities for each age class. Total population and fertility were calculated with the values in the 100,000s due to difficulties with running the model with very large values.

1

10

100

1000

10000

100000

0 5 10 15 20 25

Nu

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in 1

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,00

0s)

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Age-Structured Populations: Median Total Population

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Sensitivity and Elasticity Analysis:

Populations at different stage classes experience changes at different intensities. A

sensitivity analysis helps identify the life-history stage that will contribute the most to

population growth for summer flounder. A stable-stage distribution was calculated to form

the left eigenvector. Results showed that by year 26 the population stabilized at an

asymptotic population growth rate (λt) of 1.051. Since λt is greater than 1, the number of

individuals in the population increases geometrically by 5% per time step (year). Figure 10

shows that larvae consist of 99% of the distribution. The remaining 1% is divided into the

largest distribution being the youngest stage (Juvenile I) and the smallest distribution

being the second oldest stage (Adult IV). Adult V is not the smallest stage distribution

because it is a grouped stage with individuals >7 years old.

Figure 10: Stable Stage Distribution calculated from the sensitivity and elasticity analysis. Larvae compose 99% of a stable population. Pattern shows older stages comprising a smaller distribution.

In order to determine how to further increase to λt increase the population, a sensitivity

and elasticity analysis was performed. The sensitivity analysis generated in Table 4

determined that small changes in Juvenile II would create the largest effect on λt. Juveniles

II created a sensitivity value of 0.2027, in contrast to Adults I with 0.1322. The sensitivity

values decreased with increasing age classes, meaning that younger age classes create a

Larvae 0.999998152

Juveniles I 0.000000630

Juveniles II 0.000000459

Adult I 0.000000317

Adult II 0.000000189

Adult III 0.000000114

Adult IV 0.000000063

Adult V 0.000000077

Other 0.000001848

Stable Stage Distribution

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larger change in λt. The sensitivity analysis concluded that Juveniles II was most sensitive

to changes when fecundity is changed, as depicted in Table 5. Thus the juvenile stage

should be focused on during conservation efforts since that are critical in changing λ.

Table 4: Sensitivity matrix for summer flounder. Juveniles II are the most sensitive population stage.

Sensitivity Matrix

F(l) F(j1) F(j2) F(a1) F(a2) F(a3) F(a4) F(a5)

Larvae (0) 0.384486 0.00000024 0.00000018 0.00000012 0.00000007 0.00000004 0.00000002 0.00000003

Juveniles I (1) 377896.6 0.2381 0.1733 0.1198 0.0713 0.0432 0.0237 0.0289

Juveniles II (2) 321611.3 0.2027 0.1475 0.1019 0.0607 0.0367 0.0202 0.0246

Adult I (3) 288186.4 0.1816 0.1322 0.0544 0.0544 0.0329 0.0181 0.0221

Adult II (4) 298050.7 0.1878 0.1367 0.0945 0.0562 0.0341 0.0187 0.0228

Adult III(5) 299533.3 0.1888 0.1374 0.0949 0.0565 0.0342 0.0188 0.0229

Adult IV (6) 329220.0 0.2075 0.1510 0.1044 0.0621 0.0376 0.0206 0.0252

Adult V (7+) 358211. 0.2257 0.1643 0.1135 0.0676 0.0409 0.0225 0.0274

Due to the limitations of comparing survival rate probabilities to fecundity, an elasticity

analysis was also performed. Elasticity analyses are even more important when

determining critical stages in population growth. Fecundity and survival are placed in the

same scale, allowing comparison of the two factors. Results showed that Juveniles I survival

and Adult V fecundity are most influential in changing λ (Table 5).

Table 5: Elasticity matrix for summer flounder. Juvenile I survival and Adult V fertility have greatest effect on λ

Elasticity Matrix

F(l) F(j1) F(j2) F(a1) F(a2) F(a3) F(a4) F(a5)

Larvae (0) 0 0 0 0.03337 0.06128 0.05614 0.04327 0.19040

Juveniles I (1) 0.23813 0 0 0 0 0 0 0

Juveniles II (2)

0 0.14749 0 0 0 0 0 0

Adult I (3) 0 0 0.09134 0 0 0 0 0

Adult II (4) 0 0 0 0.05624 0 0 0 0

Adult III(5) 0 0 0 0 0.03422 0 0 0

Adult IV (6) 0 0 0 0 0 0.02063 0 0

Adult V (7+) 0 0 0 0 0 0 0.01234 0.01508

20 | P a g e

Figure 11 shows how on Adult V is the only stage that remains in the stage class. The value

used in the matrix is the same value as Adults IV. The original calculation has a larger value

than Adults IV because Adult V is grouped. In order to minimize error in the results, the

value of Adult IV was used. In addition, the figure shows how elasticity values for remaining

in the stage class decrease with increasing age.

Figure 11: Summer Flounder elasticity values for the survival values, Pi,i and Pi,i+t for each stage class

When comparing the effect that fecundity and survival have on λ, a single stage can be

determined to be the most influential on λ. Figure 12 shows a comparative approach at

examining the influence each stage class, regardless of factor, has on λ. The results show

that Larvae survival has the greatest influence and Adult V fecundity as the second greatest

influence. For Adults I through Adults IV, the survival and fecundity of each stage is very

small compared to other stage classes. Juveniles I and II express moderate elasticity when

changes are seen. It can be concluded that although Juveniles II is most sensitive, Larva and

Adults V can increase λ by a factor of 0.23813 and 0.1904, respectively.

0

0.05

0.1

0.15

0.2

0.25

0.3

Larva Juv I Juv II Adults I Adults II Adults III Adults IV Adults V

Ela

stic

ity

Elasticity Values for Remaining in Stage Class (Red Bars) and Graduating to Next Stage Class (Blue Bars)

21 | P a g e

Figure 11: Comparative analysis of fecundity and survival estimates from the elasticity analysis. Larva and Adults V show greatest influence on λ. Adults I to Adults IV show both low fecundity and survival values.

Overall, Juveniles II should be closely conserved since changes in that stage greatly affect λ.

In addition, Larva survival and Adults V fecundity have great influence in increasing the

population growth rate of summer flounder populations.

CONSERVATION & MANAGEMENT STRATEGY

Data Collection Methods:

Data for summer flounder are collected from each region’s individual survey trawls. Lack of

uniformity in data has caused bias in length, age, and sex-frequency of discards. Therefore

in order to develop more accurate data models, a more consistent program needs to be in

place to ensure data collection is followed by more specific guidelines.

A concern that all fisheries have in regards to summer flounder sustainability is the

limitation in data quantity and quality. The data that needs serious improvement is

discards, bycatch, and tagging data. Discards are when a species is thrown overboard after

0

0.05

0.1

0.15

0.2

0.25

0.3

Larva Juv I Juv II Adults I Adults II Adults III Adults IV Adults V

Ela

stic

ity

Elasticity Values for Survival and Fecundity Estimates

Survival

Fecundity

22 | P a g e

being caught, either because the minimum required size hasn’t been met or the bag limit

has been reached. Another important example of discard is in commercial fisheries when

nets are used. If a net is full of catch and is hauled out of the water, the fish at the bottom of

the net usually get crushed by the weight of the fish above it. These crushed fish are

considered discards since they cannot be stored and sold. The inability and lack of

regulation to require fisherman to thoroughly collect the weight of discards or individuals

discarded is a major flaw in summer flounder data statistics. Discard data can provide a

better estimate as to the total population size. NOAA predicts the discard to be around

10%; however, all summer flounder management studies have stated that discards are

underrepresented.

Stock productivity of summer flounder are currently determined by the spawning stock

biomass (SSB) of reproducing individuals; however, fecundity rates (and egg condition) for

a stock has the potential to be a better indicator stock productivity than weight. Also,

studies involving the productivity of summer flounder disagree between the peak sexual

maturities of adults and when adulthood, on average, actually begins. Proper collection of

age data, through otolith examination, could be used to assist in proper determining the

sexual maturity and fecundity rates. More research needs to be conducted to create

procedures of determining age and sex of summer flounder during survey trawls.

Juveniles - Class and Habitat Conservation:

Juveniles are the most sensitive summer flounder age class. According to the sensitivity

analysis shown in Table 4, juveniles are more susceptible to change when a change in

fertility is seen. It can be assumed that juveniles, since they are still developing and are not

participating in annual migrations, that their location can be the reason for high sensitivity.

In addition, the Larva stage is the most influential stage when increasing the population

growth of summer flounder. Larva and juvenile will stay within a single region or move

between nurseries until maturity. Because they are located for long time periods in inshore

areas, they are more susceptible to negative human effects. For example, the New Jersey

coastline is heavily populated, especially in the warmer seasons, and pollution caused by

roadways, homes, construction, and tourist sites can be having a negative impact on the

23 | P a g e

habitats to which younger summer flounder reside. The ASFMC even recognizes the shoal

waters of Cape Cod Bay and estuaries, bays, and harbors of Cape Cod are critically

important juvenile flounder habitat.

In order to protect larva and juveniles, protecting the habitats where they develop is

critical. The following are broad recommendations that regional institutions can carry out

to improve habitat quality:

prevent the loss of habitat

create buffer zones around nursery areas

develop point and nonpoint source pollution control plans

regulate animal facilities to limit wastewater discharges

reduce pesticide and agriculture runoff and improve water quality

Recreational Fishing Regulation Enforcement:

The summer flounder fishery divides catch between recreational and commercial

fisherman. 40-percent of catch is allocated to recreational fisherman and 60-percent to

commercial fisherman. Commercial fishermen are highly regulated and see high

enforcement of said regulations. Since commercial fishing has fewer people but have

significantly larger bag limits to recreational fishing, commercial is assumed to have a

greater impact on summer flounder populations. Unfortunately, it is agreed upon by the

Atlantic States Marine Fisheries Commission and NOAA that recreational fishing, due to the

lack of regulation enforcement, is having a negative impact on fishing populations. Data

that recreational fishermen collect regarding discard and catch is severely lacking. Studies

show that for every 10 catches, 1 is discarded. Improper data collection prevents accurate

assessments as to size of catch, bycatch, and tagging data. Regulation enforcers occasionally

oversee the activities of recreational fishermen, however due to the large number of

recreational fishing vessels, enforcement is difficult. It is therefore recommended that

larger fines are more enforcement on fishing from recreational fisherman is carried out.

The lack of oversight in the recreational fishing industry can lead to improper changes in

fishery management decisions for each season.

24 | P a g e

PUBLIC OUTREACH & EDUCATION

Education fishermen can be done through meetings, social media, or required by the

agencies that give out permits. Issues that can be more easily addressed are improving

tagging data collection and reducing discards of summer flounder.

The American Littoral Society is in the process of developing an interactive smartphone

app used for collecting tagging data, education fishermen on proper techniques to reduce

discards, and information updates. Recreational fishermen, being the least monitored,

produce the greatest unknown data due to lack of proper collection. The application is

meant to crowd source data for government projects to reduce the estimations behind

population size calculations.

Discards are a large source of mortality for undersized summer flounder. Recreational

fishermen in particular use more fishing poles than nets. Fishing poles have a hook that

lodges inside the summer flounder, traditionally under the gills. The American Littoral

Society has expressed interest in producing instructional videos on how to remove deep

gill hooks without mortally injuring the summer flounder. Allowing a social media

campaign to target recreational fishermen has the potential to reduce mortality and

decrease mortality from discard rates.

FURTHER RESEARCH & SUMMARY

Research on how to improve habitats for younger stage classes, improving data collection,

and examining why Adults V fecundity has large elasticity values can assist in properly

modeling summer flounder populations.

Ways in which habitats can be better conserved include:

map, characterize, and quantify important summer flounder nursery habitat

evaluate gear impacts to habitat

evaluate effects of tidal currents on all life stages

compile info on effects of environmental contaminants on the feeding, growth,

fecundity, survival, and distribution of summer flounder

25 | P a g e

Results from the elasticity analysis showed that the Adult V stage class for fecundity with

most elastic. Further research as to why it was significantly larger than the other fecundity

elasticity values needs to be conducted, even though the fact that Adults V is a grouped

stage.

Summer flounder are in very good shape based on the available data. In order to increase

the population growth of the species, the youngest stages need to be managed to ensure

optimal population growth. Regional agencies are responsible for the summer flounder in

their area, therefore efforts will be localized. Although efforts will be localized, goals should

be uniform for the benefit of the species and the economics summer flounder provide.

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REFERENCES

“57th Northewast Regional Stock Assessment Workshop (57th SAW) Assessment

Summary.” Northeast Fisheries Science Center. U.S. Department of Commerce. Aug

2013. Web. http://nefsc.noaa.gov/publications/crd/crd1314/crd1314.pdf

“60th Northeast Regional Stock Assessment Workshop (60th SAW) Assessment Report.”

Northeast Fisheries Science Center. U.S. Department of Commerce. July 2015. Web.

Nov 12 2015. http://nefsc.noaa.gov/publications/crd/crd1508/crd1508.pdf

Able, K., Sullivan, and M., Hare, J. Larval abundance of summer flounder (Paralichthys

dentatus) as a measure of recruitment and stock status. Oct 2009. Web. 09 Nov

2015.

Bigelow, M. and Schrouder. H. “Summer Flounder.” 1953. Web.

https://s3.amazonaws.com/assets.cce.cornell.edu/attachments/3634/summer-

flounder.pdf?1414173227

Dery, L.M. “Summer Flounder, Paralichthys dentatus.” Northeast Fisheries Science Center.

U.S. Department of Commerce. Web. 12 Nov 2015.

http://www.nefsc.noaa.gov/fbp/age-man/smfl/smfl.htm

Dunton, K., Jordaan, A., Conover, D., and McKown, K. “Marine Distribution and Habitat Use

of Atlantic Sturgeon in New York Lead to Fisheries Interactions and Bycatch.”

Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science,

7():18-32. May 2015. 12 Nov 2015.

“Essential Fish Habitat Source Document: Summer Flounder, Paralichthys dentatus, Life

History and Habitat Characteristics.” Northeast Fishereies Sciencfe Center. U.S.

Department of Commerce. Sept 1999. Web. Nov 12 2015.

http://www.nefsc.noaa.gov/publications/tm/tm151/tm151.pdf

“Flounders.” New Jersey Scuba Diving. May 2015. Web. Nov 12 2015.

http://njscuba.net/biology/sw_fish_flounders.php

27 | P a g e

Mid-Atlantic Fishery Management Council. 2015 Summer Flounder, Scup, and Black Sea

Bass Recreational Specifications. Mar 2015. Web. 12 Nov 2015.

http://www.greateratlantic.fisheries.noaa.gov/regs/2015/May/15sfsbsbrecspecssi

r.pdf

“Summer Flounder.” Atlantic States and Marine Fisheries Commission. Web. 15 Nov 2015.

http://pbadupws.nrc.gov/docs/ML1409/ML14097A343.pdf

“Summer Flounder.” Atlantic States Marine Fisheries Commission. Web. 09 Nov 2015.

http://www.asmfc.org/species/summer-flounder

“Summer Flounder.” Captain Dave. June 2013. Web. 15 Nov 2015.

http://www.cptdave.come/summer-flounder.html

“Summer Flounder.” Ocean Animal Encyclopedia. Nov 12 2015. Web.

http://oceana.org/marine-life/ocean-fishes/summer-flounder

“Summer Flounder.” Smithsonian Marine Station at Fort Pierce. Web. Nov 15 2015.

http://www.sms.si.edu/irlspec/Parali_dentat.htm

Terceiro, M. “Stock Assessment of Summer Flounder for 2012.” Northeast Fisheries Science

Center. 7() 12:6. Oct 2012. Web. Nov 12 2015.

http://nefsc.noaa.gov/publications/crd/crd1221/

Terceiro, M. “Stock Assessment Update of Sumer Flounder for 2015.” Northeast Fisheries

Science Center. U.S. Department of Commerce. August 2015. Web. Nov 12 2015.

http://www.nefsc.noaa.gov/publications/crd/crd1513/crd1513.pdf

“The Summer Flounder Resource.” The Summer Flounder Resource. Web. 12 Nov 2015.

http://summerflounderresourse.weebly.com/reproduction-and-development.html

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Appendix A:

Summer flounder life table used to calculate analytical models

Stage Age Total

Population

(males and

females)

Individuals in

Age Class x

(only females)

Age-

specific

survival

Fecundity

# of

individuals

dying btw

age x and

x+1

Prob. of

Dying

Before the

Next

Stage

Prob. of

Surviving

to Next

Stage

Generation

Time

Survival

Prop.

Natural

Mortality

x Nx Lx mx or bx dx qx px ~Tx Pi Natural

Mortality:

Mx

Eggs <0 121741875x105 608709375x104 --- 0 --- --- --- --- --- 0.83

Larvae 0 32260000 16130000 1.79882 0 3789500 0.234935 0.765065 0 1.324x10

-6

0.25

Post-

larvae

1 24681000 12340500 1.37621 0 3373500 0.273368 0.726632 0 0.765065 0.25

Juveniles

II

2 17934000 8967000 1.00000 0 3355000 0.374150 0.625850 0 0.726631 0.25

Adult I 3 11224000 5612000 0.62585 230000 2040000 0.363507 0.636493 431837 0.62585 0.25

Adult II 4 7144000 3572000 0.39835 697500 1512000 0.423292 0.576708 1111395 0.636493 0.25

Adult III 5 4120000 2060000 0.22973 1165000 869000 0.421845 0.578155 1338184 0.576707 0.25

Adult IV 6 2382000 1191000 0.13282 1632500 736500 0.618388 0.381612 1300975 0.57815 0.25

Adult V 7+ 3855000 1927500 0.21495 2100000 --- --- --- 3159836 1.61838 0.25

29 | P a g e

Appendix B:

Summary of population numbers from survey trawls compiled by NOAA