THE SIZE DISTRIBUTION OF BLACK SEA BASS AT ARTIFICIAL AND NATURAL REEFS

 

Overview

During the summer of 2016, I was selected for a Research Experiences for Undergraduates (REU), which is highly competitive 10-week internship, at the University of Maryland Eastern Shore (UMES) funded by National Science Foundation. During my REU, I worked with Dr. Bradley Stevens, crustacean biologist, and Cara Schweitzer, Ph.D. candidate.

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Study sites for black sea bass range from 16-32km off Ocean City, MD, between 37°and 38.5°N, at depths of 20-30m.

Non-blue head BSB

Blue Head BSB (Photo Credit: James Moncrief, UNCW)

Research question

The objective of this study is to understand the abundance and size distribution of BSB at artificial reefs, relative to that of natural reefs. Understanding the habitat characteristics that are vital to juvenile and adult BSB survival, will also help us understand how BSB diet differs relative to habitats and size. 

Why is it important? 

Because BSB are as economically important as they are, it is vital that we understand the habitats that they thrive in relative to their age and size, which could help us better understand their life cycle. Understanding which habitats are vital for BSB could provide useful information for the development of potential marine protected areas (MPA), to ensure the survival of such an economically essential species.

 

Methods

Size Distribution of BSB & Blue Head Size Frequency at Natural and Artificial Reefs

  • Recreational angling was conducted at four natural reefs and two artificial reefs (Figure 2).

  • The Angler, a 65-foot recreational angling boat used for sampling, had 40-45 anglers per sites.

  • Anglers spent approximately one hour at each site.

  • Both legal and sub-legal BSB caught were measured and identified as a non-blue head or a

  • blue head (Figure 3. A & B)

Frequency Distribution: Commercial Fishing Traps vs. Angling

  • Trap fishing consisted of standard commercial trap lines used by local Mid Atlantic Bite fishermen.

  • 3 trap lines were used at four natural reef sites (Figure 2).

  • Total length of captured BSB were measured for both legal and sub-legal.

  • Angling was conducted as previously stated on four natural sites within 1 square mile off the coast of Ocean City, Maryland.

 


Results

Size Distribution at Natural and Artificial Reefs

Figure 5. Comparing the size frequency distribution of BSB at artificial and natural reefs. There was no significant difference between sampled distribution based on reef type (Kolmogorov-Smirnov P = 0.13).

Blue Head Size Frequency

Figure 6. Comparing the proportional abundance of non-blue head BSB to blue head BSB. Blue head BSB were significantly larger than non-blue heads (P<0.001).

Blue Head Size Frequency

Figure 2. Comparing the size frequency distribution of blue head BSB captured. The sizes of Blue Head BSB caught via angling were virtually identical at both habitats (Kolmogorov-Smirnov P = 0.93).

Frequency Distribution: Commercial Fishing Traps vs. Angling

Figure 8. Comparing the size frequency distribution of BSB captured with hook and line vs. commercial traps. Sampling took place on natural bottom sites within a 1.62 km square (29 m depth). The sampled distributions were significantly different between gears (Kolmogorov- Smirnov P < 0.0001). Traps captured higher proportions of BSB from 26 -32cm, whereas angling captured higher proportions of smaller BSB (20-25 cm TL). Differences could be due to trap escape vents that release small fish.


Discussion

  • Our data showed that size distributions of BSB caught by angling at artificial and natural reefs were similar. A hypothesis of why we didn’t catch juvenile BSB is that they might not be ‘bold’ enough to attach the bait.

  • Similar size frequencies for blue head BSB in both artificial and natural habitats suggest that they may not have a preference for either type.

  • We conclude that multiple sampling methods (e.g. angling and trapping) should be used to obtain accurate measures of the size distribution of a population.

Acknowledgements 

The authors thank the National Science Foundation (NSF) for supporting the project, as well as Andre Price, Ahmed Mahmoud, Captian Wes Townson, Captian Jerhmiah Kogon, and Captain Chris Mizurak for technical assistance in collecting data for the project.


Authors

Anjali Boyd(1)*, Cara Schweitzer(2), Bradley Stevens(2)

1: Eckerd College, St. Petersburg FL,

2: University of Maryland Eastern Shore, Princess Anne, MD

*Primary/presenting author

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