[MARMAM] new paper: Foraging behavior of lactating South American sea lions and overlap with the Uruguayan fisheries

Federico Riet frietsapriza at gmail.com
Tue Nov 13 09:22:19 PST 2012

Dear colleagues,
We are pleased to announce the publication of a new paper in Deep Sea 
Research Part II that may be of your interest.

*Foraging behavior of lactating South American sea lions (**/Otaria 
flavescens/**) and spatial-temporal resource overlap with the Uruguayan 
Federico G. Riet-Sapriza, Daniel P. Costa, Valentina Franco-Trecu, 
Yamandú Marín, Julio Chocca, Bernardo González, Gastón Beathyate, B. 
Louise Chilvers, Luis A. Hückstadt

The negative impacts of the resource competition between fisheries and 
marine mammal continue to raise concern worldwide. In order to measure 
the impact, data on spatial and dietary overlap of marine mammal and 
fisheries are needed. In Uruguay the South American sea lions population 
has been dramatically declining over the past decade. The reasons for 
this population decline are unknown but may include the following: (1) 
direct harvesting; (2) reduced prey availability and distribution as a 
consequence of environmental change; or (3) biological interaction with 
fisheries or with the sympatric South American fur seal. Understanding 
the extent of the impact of the fisheries overlap or competition for 
finite food resources on the sea lion population recovery is necessary 
for effective sea lion conservation efforts and fisheries management. 
This study aims to determine resource overlap and competition between 
South American sea lions (SASL, Otaria flavescens) and the artisanal 
fisheries (AF), and the coastal bottom trawl fisheries (CBTF). This is 
conducted by integrating sea lions diet (scat analysis), spatial and 
annual consumption estimates; and foraging behavior-satellite-tracking 
data from lactating SASL with data on fishing effort areas and fisheries 
landings. Lactating females (n =10) were fitted with satellite tags and 
Time-depth recorders. We used kernel (KR) and peeled minimum convex 
polygon (95% MCP) methods for estimating the foraging utilization 
distribution of lactating SASL. Lactating SASL are benthic divers and 
are restricted to forage in shallow waters within the continental shelf. 
SASL's foraging areas overlapped with CBTF (15%) and AF (>1%) fisheries 
operational areas. In contrast, SASL dietary analysis indicated a high 
degree of overlap between the diet of SASL and the AF and CBTF fisheries 
catch. The results of this work show differing degrees of spatial 
resource overlap with AF and CBTF, highlighting a) differences in 
potential impact from each fishery; and b) that different 
management/conservation approaches may need to be taken to solve the 
fisheries-SASL conflict.

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