Size structure, distribution and interaction characteristics of dominant jellyfish from surface trawls in the Eastern Bering Sea

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1 Size structure, distribution and interaction characteristics of dominant jellyfish from surface trawls in the Eastern Bering Sea Kristin Cieciel, Lisa Eisner, Mary Courtney, and Angela Feldmann Auke Bay Laboratory, Juneau, Alaska Picture by M. Courtney

2 Outline Sampling BASIS Collection methods Species encountered Size Structure Distribution Interactions & Associations Fish species Zooplankton Temperature and salinity Conclusions Future

3 Survey design and vessels US BASIS 22-2: 2: BASIS (Bering Aleutian Salmon International Survey) Commercial trawlers Mid-Aug to mid-oct

4 BASIS Sampling Components Surface Rope Trawl: Juvenile salmon, pelagic fish, jellyfish Surface trawl (m wide X 18m deep) Zooplankton Bongo net oblique tow (33 and μm) Juday net vertical tow (16 μm m mesh) Paravet-vertical vertical tow (1 μ m mesh) Oceanography Thermosalinograph (3m) CTD (Chl a, beam c, PAR, DO) Water samples (23-2) Microzooplankton Phytoplankton Chl a: >.7 μm m (GF/F), > 2 μm, > μm, > 1 μm m size Nutrients (N, P, Si)

5 U.S. BASIS Stations Number of Sampling Stations 24 = = = 18 Sampling is weather dependent Stations are 3 nautical miles apart Bristol Bay in late Aug to early Sept Saint Lawrence in late Sept to early Oct

6 Methods All jellyfish are caught in a surface trawl (~18m). Sorted by species, weighed, and measured for bell diameter. Diameter measurements are only made on intact individuals. Based on Suchman and Brodeur methods for trawl surveys.

7 Jellyfish typically caught in trawl Chrysaora melanaster Cyanea capillata Phacellophora camstichatica Staurophora mertensi Aurelia labiata Aequorea sp.

8 Bering Sea Jellyfish Biomass Index of large medusae biomass during the NMFS bottom trawl survey in the Bering Sea (PICES scientific report #28, 2) Biomass (1 t) Bottom Trawl Surface Trawl Year Data made available by Robert Lauth, AFSC, Bob.Lauth@noaa.gov

9 8 7 6 Distribution of Jellyfish catch on shelf 6 24 Total weight (t) Total weight (t) Total weight (t) Inner Middle Outer North of St. Lawrence Shelf Location 48 2 Inner Middle Outer North of St. Lawrence Shelf Location Inner Middle Outer North of St. Lawrence Shelf Location

10 Frequency of Species Occurrence Frequency of Occurrence (%) Aequorea Aurelia Chrysaora Cyanea Staurophora Phaecellophora n

11 Species Composition by Location Aequorea Aurelia Cyanea Chrysaora Staurophora 1% 24 1% 2 1% 26 9% 9% 9% 8% 8% 8% 7% 7% 7% Total Catch (% ) 6% % 4% 6% % 4% 6% % 4% 3% 3% 3% 2% 2% 2% 1% 1% 1% % Inner Middle Outer North of St. Law rence Shelf Location % Inner Middle Outer North of St. Law rence Shelf Location % Inner Middle Outer North of St. Law rence Shelf Location

12 SIZE STRUCTURE

13 Aequorea sp. Oneway Analysis of Bell Diameter (mm) By Year Inner Frequency INNer Frequency Middle Frequency More Middle Frequency Bell Diameter (mm) Out er Frequency More Outer Frequency Chrysaora melanaster Year Oneway Analysis of Bell Diameter (mm) By Year Bell Diameter (mm) Inner Frequency Middle Frequency Outer Frequency More More INNer Frequency Middle Frequency Outer Frequency More More Year Oneway Analysis of Bell Diameter (mm) By Year Cyanea capillata Inner Frequency 1 1 Inner Frequency Bell Diameter (mm) Middle Frequency Middle Frequency Outer Frequency Outer Frequency Year

14 Interactions & Associations Picture by B. Stone

15 Trawl catches

16 Theragra chalcogramma Spirinchus thaleichthys Clupea pallasi Pleurogrammus monopterygius Trichodon trichodon Fish Species Ammodytes hexapterus Mallotus villosus

17 Jellyfish 24 Biomass Distributions Pollock

18 Jellyfish 24 Biomass Distributions Herring

19 EBS24; Abundance (No m -3 ) Acartia longiremis; Bongo EBS24; Abundance (No m -3 ) Centropages abdominalis; Bongo EBS24; Abundance (No m -3 ) Pseudocalanus sp.; Bongo Large Medusae EBS 24, Biomass (g m -3 ) EBS24; Abundance (No m -3 ) Calanus marshallae; Bongo Small Copepods 24 Large Copepods EBS24; Abundance (No m -3 ) Metridia pacifica; Bongo EBS24; Abundance (No m -3 ) Eucalanus bungii; Bongo

20 Temperature at m (degree C) Temperature and Salinity Data Total Gelatinous Catch (t) Station Number Temperature at m (celsius) Sallinity at m (PSU) Station Number Total Gelatinous Catch (t) Salinity (PSU)

21 Conclusions Compared with previous years, 26 shows a notable decline in jellyfish biomass Bell diameters remained relatively the same for most abundant species, with the exception of Cyanea The relationship between most forage fish catches and jellyfish catches is unclear The middle shelf has the highest concentrations of jellyfish and lowest abundance of copepods Physical ocean factors seem to influence jellyfish distributions Fluctuations in biomass seem to be occurring at an earlier life stage that our survey does not observe

22 Future Research Continuation of sampling in 27 Analyze collected oceanographic data of past years Examine possible relationships between other fish species and jellyfish Explore density-depth relationship of jellyfish

23 Fin Acknowledgements Ocean Carrying Capacity Program Crews of the Sea Storm & North West Explorer Dr. S.K Shotwell, Dr. Bruce Wing, Cara Rodgveller, & Peter Hochstoeger