New Zealand Sea Lions Historic and Present Day Threats.
-
Upload
julianna-palmer -
Category
Documents
-
view
221 -
download
1
Transcript of New Zealand Sea Lions Historic and Present Day Threats.
Life history• Estimated maximum age:
females 28yrs, males 23yrs
• Age at first reproduction:
females 4 yrs, males 9+ yrs
• Reproductive rate:
females 64%
• Adult survival not well defined – juvenile survival highly variable
• Population estimate 2008/09:
9880 (95% CI, 8604-11297)
Breeding
• Sexually dimorphic:
females 160 kgs, males 400 kg
• Dominant males hold territories, females move between territories
• Polygynous breeders: December - January
• Females nurse 8+ months
• Females are highly philopatric
• Colonial during breeding but disperse widely outside breeding season
• 68 % of all NZ sea lion dives at Auckland Islands exceed estimated ADL (4-10% for other otariids)
Mean aerobic dive limit
Feeding
Parameter Auckland Islands Otago
Age at first breeding 4yrs < 5% of all females 4yrs >85% of all females
Female mass (8-13yrs) 112 kg 152 kg
Foraging trip distance up to 175 km (ave 102km) up to 25 km
Foraging trip duration 66 hours <24 hours
Dive Depth ave 130m, max 600m ave 50m, max 110
IUCN red list 2009:
Vulnerable due to low population in decline
DoC Threat classification 2005:
Range restricted – conservation dependent
Current Population Status
Fisheries – Direct By-catchEstimated by-catch SQUID 6T 1999 - 2009
Season
FRML(revised)
Estimated total number NZ sea lion mortalities
% observer coverage
Number NZ sea lion captures on observed boats
% females caught
TotalTows
1999 64 14 37 5 80 401
2000 65 71 35 25 44 1208
2001 75 67 100 38 58 582
2002 79 84 33 22 73 1647
2003* 70 39 23 10 60 1466
2004* 62 (124) 118 31 16 88 2595
2005 115 115 29 9 67 2693
2006+ 96 (150) 110 28 11 91 2459
2007 91 56 41 8 75 1318
2008 81 46 47 5 60 1247
2009 113 (95) 72 38 4 75 1916
Total 780 153 Ave. 70% 17205* Court ruling allowed fishing to continue after FRML reached
+ Minister of Fisheries increased FRML at request of fishery
Diet of the New Zealand sea lion occurrence (%O), number (%N) and mass (%M)
TOTAL (121 stomachs) DIGESTED (112 stomachs)
1 to 2+ days before death
FISH %O %N %M %O %N %M
Jack Mackerels 8.2 0.7 3.0 7.1 0.7 2.6
Warehou 4.1 0.2 1.0 2.7 0.1 1.2
Pigfish 11.5 0.7 0.1 9.7 0.6 0.1
Barracouta 7.4 0.5 4.6 5.3 0.5 5.8
Javelin fish 9.0 3.3 0.4 7.1 4.3 0.7
Hoki 11.5 2.2 9.6 12.4 3.1 15.5
Red cod 32.0 3.1 3.2 30.1 3.8 4.3
Ling 13.1 0.9 4.4 14.2 1.5 8.8
Opalfish 48.4 35.5 2.4 50.4 50.1 4.7
CEPHALOPODS
Octopus 38.5 3.1 14.4 28.3 2.1 27.8
Arrow squid 86.9 33.4 43.0 33.6 14.1 17.9
Total number of taxa/species 35 29
Protection measures
• Marine mammal protection act:- it is an offence, amongst other things, to harass or disturb marine mammals;- offences carry penalties of up to 6 months imprisonment or fines up to $250,000 and further fines of up to $10,000 for every marine mammal in respect of which the offence is committed;- marine mammals caught accidentally or incidentally in fisheries must be reported
• Marine mammal sanctuary:since 1994 there has been a 12 n.mile marine mammal sanctuary around the Auckland Islands
Protection measures• Fisheries Act:
- the Minister may take measures considered necessary to avoid, remedy, or mitigate the effect of fishing-related mortality on any protected species (ie Fisheries Related Mortality Limit, FRML)
• FRML:- in place since 1992- FRML supposed to allow population growth- bycatch estimated using historical catch data when observer coverage was low and has not been adjusted to account for 50% longer tows- model used to calculate FRML severely limited (unable to fit estimated reproductive rate)- FRML does not include other fisheries (just SQ 6T)- legal challenges have allowed continuation of fishing after FRML has been passed.