Seabird Use of Discards from a Nearshore Shrimp Fishery in the South Atlantic Bight, USA
Electronic supplement for:
Seabird use of discards from a nearshore shrimp fishery in the South Atlantic Bight, USA
Patrick G.R. Jodice, Lisa C. Wickliffe, and Elena B. Sachs
Contents:
Table S1: Models relating seabird abundance (SUM)a, Julian date within year (JD), study area (SA), year (YR), and time block within day (TB)b to the success index (SI) of each of the four most commonly observed species of seabirds foraging at shrimp trawlers operating in nearshore waters of South Carolina, USA, May–August 2006 and 2007.
Table S2: Models relating seabird abundance (SUM)a, Julian date within year (JD), study area (SA), year (YR), time block within day (TB)b, taxonomic order of discarded item (TAX)c, species of discarded item (SPP), and length of discarded item (LEN)d to the fate of items experimentally discarded from shrimp trawlers operating in nearshore waters of South Carolina, USA, May–August 2006 and 2007.
Table S1. Models relating seabird abundance (SUM)a, Julian date within year (JD), study area (SA), year (YR), and time block within day (TB)b to the success index (SI) of each of the four most commonly observed species of seabirds foraging at shrimp trawlers operating in nearshore waters of South Carolina, USA, May–August 2006 and 2007.
Model / Hypothesis description / Model structure1 / SI constant / Intercept only
2 / Count affected by seabird abundance / SUM
3 / Count affected by Julian date within year / JD
4 / Count affected by year (2006 or 2007) / YR
5 / Count affected by time of day (four time blocks) / TB
6 / Count affected by study area (CharlestonHarbor or CapeRomain) / SA
7 & 8 / Count affected by study area and abundance (with and without interaction) / SA + SUM; SA + SUM + (SA * SUM)
9 & 10 / Count affected by date and year (with and without interaction) / JD + YR; JD + YR + (JD * YR)
11 & 12 / Count affected by study area and date (with and without interaction) / SA + JD; SA + JD + (SA * JD)
13 & 14 / Count affected by study area and year (with and without interaction) / SA + YR; SA + YR + (SA * YR)
15 & 16 / Count affected by study area and time (with and without interaction) / SA + TB; SA + TB + (SA * TB)
17 & 18 / Count affected by time and date (with and without interaction) / TB + JD; TB + JD + (TB * JD)
19 / Count affected by date and abundance / JD + SUM
20 / Global / All main variables and two-way interactions
a Seabird abundance measured as the total count of birds present during the most recent seabird survey which occurred every 40 mins (see Wickliffe 2007 for a description of survey methods used to estimate seabird abundance).
b Time block (TB) 1= sunrise + 3hrs, TB 2 = end of TB 1 to sunrise + 6hrs, TB3 = end of TB2 to sunrise + 9hrs, TB 4= end of TB 3 to sunrise +12hrs.
Table S2. Models relating seabird abundance (SUM)a, Julian date within year (JD), study area (SA), year (YR), time block within day (TB)b, taxonomic order of discarded item (TAX)c, species of discarded item (SPP), and length of discarded item (LEN)d to the fate of items experimentally discarded from shrimp trawlers operating in nearshore waters of South Carolina, USA, May–August 2006 and 2007.
Model / Hypothesis description / Model structure1 / Fate constant / Intercept only
2 / Fate affected by seabird abundance / SUM
3 / Fate affected by Julian date within year / JD
4 / Fate affected by year (2006 or 2007) / YR
5 / Fate affected by time of day (two time blocks) / TB
6 / Fate affected by study area (CharlestonHarbor or CapeRomain) / SA
7 / Fate affected by length / LEN
8 / Fate affected by taxonomic order / TAX
9 / Fate affected by species / SPP
10 & 11 / Fate affected by study area and taxonomic order (with and without interaction) / SA + TAX; SA + TAX + (SA * TAX)
12 & 13 / Fate affected by date and taxonomic order (with and without interaction) / JD + TAX; JD + TAX + (JD * TAX)
14 & 15 / Fate affected by length and date (with and without interaction) / LEN + JD; LEN + JD + (LEN * JD)
16 & 17 / Fate affected by study area and length (with and without interaction) / SA + LEN; SA + LEN + (SA * LEN)
18 / Global (with taxonomic order) / All main variables and two-way interactions
19 / Global (with length) / All main variables and two-way interactions
a Seabird abundance measured as the total count of birds present during the most recent seabird survey which occurred every 40 mins.
b Time block (TB) 1= 0600 h-1100 h, TB 2 =1101 h-1700 h.
c Length categories of discarded items were 50–99 mm, 100–199 mm, 200-399 mm, and 400–600 mm.
d Taxonomic orders were clupeiformes, pleuronectiformes, perciformes and other (teuthida, tetraodontiformes, decapoda, aulopiformes, and scorpaeniformes which made up 2% of the fish discarded).