This Forni_et_al_readme.txt file was generated on 2022-01-27 by Paola Forni

GENERAL INFORMATION

1. Title of Dataset: Stomach content and body score of Long-tailed duck collected during wintering period in the South-Eastern Baltic Sea

2. Author Information
	A. Principal Investigator Contact Information
		Name: Paola Forni
		Institution: Klaipeda University
		Address: H. Manto, 84 92294 Klaipeda
		Email: paola.forni@ku.lt

	B. Associate or Co-investigator Contact Information
		Name: Julius Morkunas
		Institution: Klaipeda University
		Address: H. Manto, 84 92294 Klaipeda
		Email: julius.morkunas@apc.ku.lt

	C. Alternate Contact Information
		Name:Darius Daunys 
		Institution: Klaipeda University
		Address: H. Manto, 84 92294 Klaipeda
		Email: darius.daunys@ku.lt

3. Date of data collection: November-May, 2016-2020. 

4. Geographic location of data collection: South-Eastern Baltic Sea, Lithuanian coastal waters, area within Lat 55.967810, Long 21.069638 until areas with Lat 55.455808, Long 21.066381. 

5. Information about funding sources that supported the collection of the data: Klaipeda University's PhD program 


SHARING/ACCESS INFORMATION

1. Licenses/restrictions placed on the data: CC0

2. Links to publications that cite or use the data: 

3. Links to other publicly accessible locations of the data: N.A.

4. Links/relationships to ancillary data sets: N.A.

5. Was data derived from another source? No
	

6. Recommended citation for this dataset: https://doi.org/10.5061/dryad.fxpnvx0th


DATA & FILE OVERVIEW

1. File List: 
Single excel file: contains information about the individual long-tailed duck (identification code, date of entanglement in gillnet, sex, age, 
benthic substrate type in the area where the indivudual was collected, values of intestinal and subcutaneous, together with the value of the pectoral muscle and the body score) 
and abundance and biomass of the taxa found in the diet of long-tailed ducks. 

2. Relationship between files, if important: not applicable

3. Additional related data collected that was not included in the current data package: not applicable

4. Are there multiple versions of the dataset? no
	


METHODOLOGICAL INFORMATION

1. Description of methods used for collection/generation of data:
The stomach content of 267 long-tailed duck individuals accidently bycaught in fishermen’s gillnets between 2016 and 2020 from November to May. 
Before the collection of stomach samples, long-tailed ducks were weighted and dissected for the determination of sex, age and body index. 
Stomach content samples were frozen at -20 °C after individuals were removed from the bycatch until the analysis. 
Before the analysis, stomach samples were defrosted and rinsed with clean water. 
The prey items were removed and sorted for taxonomic identification to the lowest possible taxonomic unit and for the determination of abundance and biomass. 
The ability to count prey individuals depended on the level of digestion. The intact prey items were counted and weighted. 
Bivalve shells, fish otoliths and polychaete jaws, were paired and used to estimate the preys’ abundance as explained in Camphuysen and Leopold (2007).
All taxonomically identified prey fragments were weighted and used for characterisation of the biomass of a given prey taxa. 
The biomass was measured as wet weight with an accuracy of ± 0.0001 g after excess water was removed using filter paper. 
This approach ensured comparability of our results with those obained in the study of Žydelis and Ruškyte (2005).
The body index was estimated by evaluating and summing intestinal fat, subcutaneous fat and the condition of the pectoral muscle. 
Fat deposits were scored from 0 (no fat) to 3 (very fat).
The same procedure was used to determine the condition of pectoral muscle, where 0 was a strongly emaciated pectoral muscle and 3 was a muscle in good condition.

References:
Van Franeker, J.A. Save the North Sea Fulmar-Litter-EcoQO Manual Part 1: Collection and dissection procedures. Wageningen, Alterra, Alterra-rapport 672. 2004, pp. 40
Camphuysen, C.J.; Leopold, M.F. Diet study manual for stranded seabirds. Technical documents 4.1, Handbook on Oil Impact Assessment, version 1.0., 2007
Žydelis, R.; Ruškyte, D. Winter foraging of long-tailed ducks (Clangula hyemalis) exploiting different benthic communities in the Baltic Sea. Wilson Bulletin 2005, 117(2): pp. 133-141

3. Instrument- or software-specific information needed to interpret the data: 
To interpret the data, we employed R software (WRS2 package) and Sigmaplot software (Systat Software Inc.) for non-parametric analysis.

4. Standards and calibration information, if appropriate: not applicable

5. Environmental/experimental conditions: not applicable

6. Describe any quality-assurance procedures performed on the data: not applicable

7. People involved with sample collection, processing, analysis and/or submission: 
Modestas Bružas: collecting and dissecting birds
Veronika Biveinytė : analysing part of stomach analysis
Dr. Laura Šaltytė-Vaisiauskė:  advices on statistical data analysis. 
Julius Morkunas: collecting long-tailed ducks, dissecting and processing
Darius Daunys: analysis, writing and submission


DATA-SPECIFIC INFORMATION FOR: Forni et al abundance biomass stomach content of long-tailed duck

1. Number of variables: 44

2. Number of cases/rows: 251

3. Variable List: 
Code: identification code of the individual long-tailed duck 
Date: Date of the duck collection from the fishermen's gillnet expressed as day-month-year
Sex:  sex of the individual duck (F=female, M=male)
Substrate: csubstrate type in the locality where the long-tailed duck was bycaught (H=hard bottom, S=soft bottom)
Age: age of the individual long-tailed duck (AD=adult or JUV=juvenile)
Muscle (0-3), Subcutaneus fat (0-3), Internal fat (0-3): values from 0 to 3 given according to the methodology from Van Franeker (2004) (reference mentioned above)
Body score: result of the sum of muscle, subcutaneous and internal fat values


4. Missing data codes: 
NA as not available. 

5. Specialized formats or other abbreviations used: 
In the abundance sheet is provided the full scientific name of the species (e.g., Saduria entomon), while in the biomass sheet the name is abbreviated (e.g., S.entomon)