Trophic understanding of of the Southwest Pacific Jock Young, Petra Kuhnert, Jessica Farley, Shane Griffiths, Adrian Flynn, Matt Lansdell, Robert Olson PFRP PI Meeting, University of Hawaii November 2012

WEALTH FROM FLAGSHIP Tunas and Their : Safeguarding Sustainability in the 21st Century

• What do we know and where to now? • 16 chapters, Chapter 3 on trophic ecology (CLIOTOP Working Group 3) • Trophic ecology • Chemical indicators • Bioenergetics • Niche separation • Climate change • Research gaps

• Robert Olson, Jock Young, Valerie Allain, John Logan, Nicolas Goni, Frederic Ménard, Michel Potier Western subtropical/temperate Pacific: main species

Thunnus tonggol

Thunnus obesus

Thunnus albacares

Thunnus alalunga

Thunnus maccoyii

3 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Western subtropical/temperate Pacific

Species SCA DR SIA SFA

Thunnus alalunga + + + 0

Thunnus albacares + + + 0

Thunnus maccoyii + + + 0

Thunnus obesus + + + 0

Thunnus tonggol + + 0 0 Katsuwonus pelamis 0 0 0 0

+ = data exist for this region 0 = no data exist for this region NA = this species does not occur in this region

4 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY SAMPLE COLLECTION

(Data span 1992 -2010)

Campbell and Young 2012, Flynn and Paxton in press, Griffiths et al 2007 Revill et al 2009 Young et al 1997,2001, 2010, 2011

5 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY sampling (circled n=533) for stable isotopes in the western Pacific

(Farley et al in press)

6 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Trophic understanding of tunas of the Southwest Pacific Ocean

Trophic ecology Chemical indicators Bioenergetics Niche separation Climate change

7 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Diet comparisons

(Griffiths et al 2007, Young et al 2010) Classification trees to identify relative importance of environmental and biological variables: case study of

Parameters in order of importance: Season, latitude, SST Predictive capacity e.g at node 6 predicts that in winter, in southern waters the diet of yellowfin tuna will be composed of a mix of species.

In contrast, in summer, in mid latitudes at SST> 19C diet of yellowfin tuna composed mainly of megalopa

(Kuhnert et al 2012)

9 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Other functions: Prey diversity and partial dependence plots

Kuhnert et al 2012

10 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Predator-Prey relationships

Quantile regression analysis Longtail tuna (Francis Juanes)

30 Albacore 15 N = 0 20 Yellowfin tuna 10 N = 9 0

12 Southern bluefin… N = 1 6 0 20 length 10 N = 1

0 1-20 600+

61-80 (Griffiths et al 2007; 121-140 181-200 241-260 301-320 361-380 421-440 481-500 541-560 Young et al 2010)

11 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Vertical distribution and feeding times

15 Yellowfin… 10 5 0 18 Albacore 12 6 0

6 Bigeye tuna 4 2 0 0 4 8 12 16 20 (Campbell and Young 2012) feeding

• Bestley et al 2008, 2010, Young et al 1997 • Main feeding occurring around dawn. Night feeding, although rare on the full moon

• Multiple-day fasting periods were recorded by most individuals. The Inshore majority of these occurred during periods of residency EAC within warmer waters 1992 1993 1994

Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Seasonal feeding events

(Flynn and Paxton in press)

14 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Trophic understanding of tunas of the Southwest Pacific Ocean

Trophic ecology Chemical indicators Bioenergetics Niche separation Climate change

15 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Trophic groupings off eastern Australia

(Revill et al 2009)

16 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY 15 Albacore δ N (533 fish sampled)

length

year

sex

GAM Best model included Year, Sex, length, long and lat. Age ns (explained 55% Variation). *Age ns (Kuhnert et al CSIRO unpubl.) 13 Albacore δ C (533 fish sampled)

length

year

GAM model included Year, Age, length, long (Kuhnert et al CSIRO unpubl.) and lat (explained 47% of the variation) Compound specific amino acids of albacore from the south western Pacific (n=30) Source amino acid

ns (Revill et al CSIRO unpubl.)

19 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Signature fatty acids ( only)

Myctophid prey Swordfish trophic relationships: Stress: 0.06

Squid

Other fish 34S 24S

Myctophids Swordfish & prey Swordfish Young et al. Prog. Oceanog. (2010)

FA data %, not transformed or standardised, based on a Bray Curtis similarity matrix Trophic understanding of tunas of the Southwest Pacific Ocean

Trophic ecology Chemical indicators Bioenergetics Niche separation Climate change

21 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Daily Ration

SPECIES DAILY RATION (%) REF Thunnus alalunga 0.48 Young et al 2010 Thunnus albacares 1.65 Young et al 2010 Thunnus obesus 1.71 Young et al 2010 Thunnus tonggol 2.36 Griffiths et al 2007

Thunnus maccoyii 1.70 Young et al 1997

•Energy consumption and daily ration needed for Q/B ratio in ecosystem models

22 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Daily ration (%BW per day)

3.5

•Variability within and between species 3 •Variability between sizes •Variability bw regions 2.5 •Variability between inshore and 2 offshore waters Daily ration inshore

1.5 Daily ration offshore

1

0.5

0 ALB BET SBF YFT LOT

*SBF 0.75 Kg per fish (Bestley et al 2008)

23 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Trophic understanding of tunas of the Southwest Pacific Ocean

Trophic ecology Chemical indicators Bioenergetics Niche separation Climate change

24 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Segregated feeding niches – time of day, depth, prey type and size

Young et al 2010

25 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Tropical tunas

Inshore Offshore

Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Temperate tunas

(work in progress)

Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Trophic understanding of tunas of the Southwest Pacific Ocean

Trophic ecology Chemical indicators Bioenergetics Niche separation Climate change

28 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY Climate change – 20% decrease in micronekton

Toothed whales Green sea turtles Leatherback turtles Seabirds Pelagic Large sharks Hammerhead sharks Blue Black marlin Blue marlin Striped marlin Spearfish Swordfish (adult) Swordfish (juvenile) Yellowfin tuna (adult) Yellowfin tuna (juvenile) Bigeye tuna (adult) Bigeye tuna (juvenile) SBT (adult) SBT (juvenile) Albacore Skipjack Medium scombrids and dolphinfish Small scombrids and carangids Lancetfish Large mesopelagic fishes Medium mesopelagic fishes Small mesopelagic fishes Micronekton fishes Epipelagic Small mesopelagic squids Medium mesopelagic squids Large mesopelagic squids Sunfish Opah Pelagic triggerfishes/pufferfishes Epipelagic beloniform fishes Small clupeids/engraulids Mesopelagic Epipelagic zooplankton Mesopelagic zooplankton Gelatinous zooplankton Primary producers Detritus Griffiths et al 2010 0.5 1 1.5 Biomass (End / Start) Climate change – 50% increase in squids (4 groups)

Toothed whales Green sea turtles Leatherback turtles Seabirds Pelagic mackerel sharks Large sharks Hammerhead sharks Blue shark Black marlin Blue marlin Striped marlin Spearfish Swordfish (adult) Swordfish (juvenile) Yellowfin tuna (adult) Yellowfin tuna (juvenile) Bigeye tuna (adult) Bigeye tuna (juvenile) SBT (adult) SBT (juvenile) Albacore Skipjack Medium scombrids and dolphinfish Small scombrids and carangids Lancetfish Large mesopelagic fishes Medium mesopelagic fishes Small mesopelagic fishes Micronekton fishes Epipelagic squids Small mesopelagic squids Medium mesopelagic squids Large mesopelagic squids Sunfish Opah Pelagic triggerfishes/pufferfishes Epipelagic beloniform fishes Small clupeids/engraulids Mesopelagic crustaceans Epipelagic zooplankton Mesopelagic zooplankton Gelatinous zooplankton Griffiths et al 2010 Primary producers Detritus

0.5 1 1.5 Biomass (End / Start) Interannual variations in prey composition

88 529 100 348363 416 333 206 126 109 23544 40 600 125

12 ) 1 - 80 9 60 6 40 Prey.kg Pred Prey.kg 3 Prey Biomass (g 20

0 Prey (%) Prey Proportion 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Year Year

(Young et al 2010)

31 | Trophic understanding of tunas of the Southwest Pacific Ocean| JWY SUMMARY

• General understanding of trophic relations of tuna in the southwest Pacific with exception of skipjack • Development of statistical techniques to quantify the importance of environment and biology in tuna diets • The potential for using chemical indicators as part of “typical” measures (e.g. age, reproduction) of tuna life history • Importance (and lack of) interannual studies and their application to ecosystem models • Need for spatially and temporally rigorous collections of appropriate samples to support wider life history collections (see Allain et al 2012, Nicol et al 2012)

Thank you Jock Young

+61 3 6232 5360 e [email protected]

Division of Marine and Atmospheric Research

WEALTH FROM OCEANS FLAGSHIP