An investigation of morphological characteristics of spot croaker from Assateague Island
Transcript of An investigation of morphological characteristics of spot croaker from Assateague Island
An investigation of morphological characteristics of spot croaker (Leiostomus xanthurus)
and white mullet (Mugil curema) from Assateague Island National Seashore, Virginia
Lee PuttENVT450 Environmental Studies Capstone
23 April 2014
Introduction to Common Atlantic Coastal Fishes
• Spot croaker, also known as spot, and white mullet are some of the most common species – very abundant, heavily fished and staple prey item– Inhabit shallow coastal waters , bays, beaches, and estuaries with sandy or
muddy bottoms and submerged vegetation as well as open water habitat
Range of Spot and White Mullet
• Broad range – from New Brunswick to Mexico
• Habitat diverse and varies – from shallow grassy beds, to open water
Tom’s Cove Off the Coast of Assateague Island
Importance of Coastal Habitats to Fish Populations
• Many species of fish coastal regions as nursery grounds • Play an important role in wetland and terrestrial food chains • As fish grow larger, often graduate to deeper water until they
completely migrate out into the open ocean
• Spot utilize the inlets and coves for nursery grounds
Objectives • Objective 1: to contrast body shapes of spot and white mullet using
geometric morphometric analyses to demonstrate how effectively these techniques distinguish interspecific differences
• Objective 2: to investigate if intraspecific body shape differences could be detected and correlated with variations in habitat for spot
Materials and Methods• In total, 33 white mullet and 108 spot were collected• Fish collected and euthanized in the field as required by the collection permit
Queen’s Sound – Intermediate Habitat
Inlet of Tom’s Cove – Shallow
Water
Offshore of Assateague Island –
Open Water
Fish Collection in Tom’s Cove
Fish Collection in Queen’s
Sound
Fish Collection off the Coast of
Assateague Island
Materials and Methods To Measure Shape Differences Among Fish:• Geometric morphometrics utilizes the X
and Y coordinates on an axis to conduct multivariate analyses
• Each fish included a unique classification number and a scale bar
• Consensus configuration– Calculates an average shape of the fish
through marked locations
• Relative warp analyses– Provides a visually benefit which shows shape
differences across the sample of fish– Often shows bending
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Results – Interspecific Differences • Very distinct differences in shapes were found for white mullet and spot -
very strong interspecific differences– Also shows distinct differences in the spot population – Due to these differences, intraspecific differences were then tested on spot
White Mullet
Spot
Results – Intraspecific Differences
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67
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1314
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2526 27
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424344 45
464748
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7172
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7879
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Tom’s Cove
Open Ocean
Queen’s Sound
Discussion• The analysis of only spot agrees with other observations that body shape
differs with varying types of habitats in fish. – One study by Ruehl, Shervette, and Dewitt 2011 have found that spot and drum
collected from sea grass beds in South Carolina exhibit semi-terminal mouths – This variation in shape from the three spot populations suggest that adaptations
exist for numerous foraging techniques
Importance of Spot and Mullet• Spot and mullet are a vital part of the marine food chain in the mid-
Atlantic region• Coastal habitat is continually being stressed by overdevelopment and
pollution - if not protected, this regional food chain can become highly constricted and stressed
• Many areas in the mid-Atlantic are not protected and can be at risk from these factors– Pollution– Overfishing– Habitat destruction– Overdevelopment– Recreation – Seal Level Rise
Final Remarks• Through this study of geometric morphometrics, there are clear
interspecific differences between spot and white mullet – has been a useful tool in distinguishing statistical differences in shape
• Also shows clear intraspecific differences in spot and suggests that body shape could possibly be correlated with variations in habitat types – could be an adaptation for different foraging techniques
• Conservation strategies needs to recognize the range in habitats utilized by near-shore fish when managing this fishery
Acknowledgements I would like to thank Dr. Seiler for his invaluable insight and help with the project, the Chincoteague Bay Field Station for use of
their collecting equipment and facilities, as well as Dr. Thompson for his teaching instruction in Marine Ichthyology