Objectives

The goals of this project are to compare variations in abiotic factors

(e.g. temperature, salinity, dissolved oxygen, pH) with seasonal and

annual fluctuations in juvenile fish species life history group (e.g.

resident, migratory, transient) abundance and diversity.

Introduction

Considered among the most productive marine environments within

the Gulf of Maine (GOM), estuaries are known to provide habitat,

resources, and shelter for diverse fish communities (5). These complex

coastal ecosystems are physiologically challenging habitats due to

large variations in abiotic parameters, such as temperature, salinity,

dissolved oxygen, and pH (3,7). The Saco River Estuary (SRE) is an

established nursery ground and habitat for 60 marine, diadromous,

and freshwater fish species, including many that are considered

threatened or of commercial and recreational importance in the GOM

(1, J.A. Sulikowski; unpubl. data). Although the fish community has

been well studied in the SRE, no study to date has attempted to

correlate seasonal fluctuations in fish abundance and diversity to

environmental factors.

Materials and Methods

Throughout May – October 2013, beach seines (Figure 2A) were

conducted weekly during the day and at night at UNE’s Freddy Beach

(Figure 1). Temperature and salinity were taken during each seining

event using a YSI 30 salinity conductivity temperature system (Figure

2C). Total length (mm) and relative abundances of fish and invertebrate

species caught, expressed as catch-per-unit-effort (CPUE), were

recorded and analyzed. In addition to beach seining, modified lobster

traps (Figure 2B) were deployed at the University of New England’s

(UNE) dock to include a secondary sampling area. The traps are encased

in nylon mesh and fitted with minnow traps to increase retention.

Traps were checked daily for the aforementioned parameters. The data

were examined and interpreted in order to find correlations between

shifting fish assemblage and fluctuating abiotic factors, including the

Simpson’s diversity index using the following equation:

Acknowledgments

I would like to thank Connor Capizzano and Ryan Knotek for their help

editing my work, as well as the rest of the Sulikowski Lab for their

assistance – CW, NI, JL, AN, JL, KS, LC, BJ, JR, TB, EM, TB, AC, MK, MF,

PS, EK, AM, and SF.

A special thanks to NSF and Maine EPSCoR for funding this research as

a part of the Sustainability Solutions Initiative.

Preliminary Results

Future Application and Research

The 2012 northwest Atlantic heat wave (Figure 8) affected coastal

ecosystems by influencing the geographic distribution and seasonal

cycles of many marine species (4). In the SRE, non-native summer

flounder (Paralichthys dentatus) was introduced during this 2012 heat

wave. As climate change progresses, extreme events are expected to

become more common, which can have an effect on fisheries (4). In

addition, increasing anthropogenic influences affect condition and

recruitment of many fish species, where one poor recruitment event

can alter the status of an entire stock (2). These circumstances

combined with the commercially and recreationally important species

within the SRE strengthen the necessity to understand current

fluctuations for continued function of the fisheries within the entire

GOM ecosystem.

In order to understand the relationship between abiotic

fluctuations and the juvenile fish assemblage of the SRE, increased and

more in-depth sampling will be done throughout the 2014 field season.

In addition to the current methods of analysis, weight (g) and total

length (mm) measurements will be recorded for fish to calculate

species-specific condition factors. Water quality will be assessed by

continuing to sample temperature and salinity and also by introducing

new measurements of dissolved oxygen and pH with a YSI dissolved

oxygen meter and a Thermo Scientific Orion Star pH meter,

respectively. Furthermore, abiotic influence on fish species will be

investigated by considering freshwater discharge as a driver of

abundance and diversity.

References 1. Furey N, Sulikowski JA. 2011. The Fish Assemblage Structure of the Saco River Estuary.

Northeastern Naturalist. 18(1): 37-44.

2. Jennings S, Kaiser MJ, Reynolds JD. 2001. Marine Fisheries Ecology. Blackwell Science Ltd. v-

417

3. Loneragan NR. 1993. Defining Key Factors Relating Fish Populations in Estuaries and Their

Habitats. Bureau of Resource Sciences Proceedings. Pg. 95-105

4. Mills KE, Pershing AJ, Brown CJ, Chen Y, Chiang F-S, Holland DS, Lehuta S, Nye JA, Sun JC,

Thomas AC, Wahle RA. 2013. Fisheries Management in a changing climate: Lessons

from the 2012 ocean heat wave in the Northwest Atlantic. Oceanaography 26(2)

5. Tyrrell WC. 2005. Gulf of Maine Marine Habitat Primer. Gulf of Maine Council on the Marine

Environment, www.gulfofmaine.org/habitatprimer. vi-54.

6. US Environmental Protection Agency (EPA). 2006. Volunteer Estuary Monitoring: A Methods

Manual, Second Edition.

7. Wargo AM, Tilburg CE, Driggers WB, Sulikowski JA. 2009. Observations on the Distribution of

Ichthyoplankton Within the Saco River Estuary System. Northeastern Naturalist. 16(4):

647-654

Abiotic Influences on the Juvenile Fish Assemblage

of the Saco River Estuary, Maine

Brenda N. Rudnicky, Julia M. Reynolds, Kayla M. Smith, James A. Sulikowski Ph.D.

University of New England, Marine Sciences

Figure 2. Equipment used during the study: (A) beach seine, (B) modified

lobster trap, and (C) YSI 30 salinity conductivity temperature system.

A B

Figure 1.Sampling locations along the Saco River Estuary; (A) UNE dock (trap

deployment) and (B) Freddy Beach (beach seines).

Figure 5. Species abundance (expressed in CPUE) and richness

(expressed by number of species present) for Freddy Beach,

2013.

Figure 8. Average monthly water

temperatures for 2012 and 2013 at Freddy

Beach.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

May June July August September October

Percen

tage of C

atch

Month

resident non resident

Figure 6. Resident vs. non-resident fish abundance for the SRE,

2013.

Figure 7. Distributions of resident, marine non-resident, and

freshwater non-resident species between fresh and oligohaline

water (0-5ppt) (10 seining events) and mesohaline water (5-18ppt)

(14 seining events). Saline water classifications from the EPA’s

Volunteer Estuary Modeling Manual (6).

A B

C

Figure 3. Freddy Beach most abundant species in (A) 2010, (B) 2011, (C) 2012, and (D) 2013. Species abundance of juvenile fish

species in the SRE fluctuates on annual temporal scales. The results represent 88% ± 8.62% of total catch for each year.

D C B A

0

1

2

3

4

5

6

7

8

0

0.2

0.4

0.6

0.8

1

1.2

May June July August September October

Nu

mb

er of sp

ecies

CPU

E

Month

CPUE species richness

Table 1. Juvenile fish species captured in the SRE from 2010-

2013. Species are identified based on commercial or

recreational importance (**), as a federally listed species of

concern (*), or both (***). Life history classifications include:

m(a): marine anadromous, m(c): marine catadromous, t:

transient, r: resident, f: freshwater, and nn: non-native.

41.2%

4.1%

89%

58.8%

95.9%

11%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Resident Marine non-residents Freshwater non-

residents

Percen

tage of C

atch

fresh and oligohaline mesohaline

A

C

B

D

E

Figure 4. Example juvenile fish from the SRE: (A) Atlantic

herring, (B) striped bass, (C) rainbow smelt, (D) winter

flounder, and (E) bluefish.

0

5

10

15

20

25

30

May June July Aug Sept Oct

tem

peratu

re (˚C

)

Month

2012 2013

Figure 9. Summer flounder

(Paralichthys dentatus).

n = total number of

individuals of a

single species

N = total number of

individuals caught

American

sand lance

24.32%

mummichog

5.50%

mummichog

2.86%

Common

name

Scientific

name

Life

history

alewife * Alosa pseudoharengus m(a)

American eel ** Anguilla rostrata m(c)

American sand lance Ammodytidae americanus t

Atlantic herring ** Clupea harengus t

Atlantic menhaden ** Brevoortia tyrannus t

Atlantic silverside Menidia menidia r

Atlantic tomcod Microgadus tomcod t

banded killifish Fundulus diaphanus r

blueback herring * Alosa aestivalis m(a)

bluefish ** Pomatomus saltatrix t

fourspine stickleback Apeltes quadracus r

largemouth bass ** Micropterus salmoides f

longhorn sculpin Myoxocephalus

octodecimspinosus

t

mummichog Fundulus heteroclitus r

ninespine stickleback Pungitius pungitius r

northern pipefish Syngnathus fucus t

pumpkinseed Lepomis gibbosus f

rainbow smelt *** Osmerus mordax m(a)

red hake ** Urophycis chuss t

smallmouth bass ** Micropterus dolomieu f

spottail shiner Notropis hudsonius f

striped bass ** Morone saxatilis t

striped killifish Fundulus majalis r

striped mullet Mugil cephalus t

summer flounder Paralichthys dentatus nn

threespine stickleback Gasterosteus aculeatus r

windowpane flounder ** Scophthalmus aquosus t

winter flounder ** Pseudopleuronectes

americanus

t