Interannual variability of Humboldt squid (Dosidicus gigas) occurrence in the
northern California Current System is largely unknown. In Oregon, the distribution of
this versatile predator and what is influencing their range expansion from Mexico is
poorly understood due to the recent nature of their "invasion" and a lack of
monitoring. Humboldt squid are large predators that have the potential to affect
ecosystem structure and fisheries because of their high-energy demands and ability to
exploit a variety of oceanographic conditions and prey sources. Developing baseline
distribution information is a critical first step to assess their potential ecological,
social, and economic impacts, and to develop models to predict future range
expansion.
This study has two main objectives: (1) to document where and when
Humboldt squid have been present in Oregon through cooperative fisheries research,
and (2) to correlate the sightings with oceanographic conditions using a geographic
information system (GIS) and species distribution modeling (SDM). I conducted 54
interviews with local fishermen and aggregated their squid sightings with available
fishery-independent survey and fishery-dependent observer data from the National
Marine Fisheries Service. I compiled a total of 339 Humboldt squid sightings,
reported for the years 2002-2011 from the Oregon coast to 131�� west longitude.
Correlation analyses were performed for Humboldt squid sightings and sea surface
temperature (SST), chlorophyll a content (chla), sea surface height anomalies (SSH),
dissolved oxygen at 30 m depth (30 m DO), and sea surface salinity (SSS) using a
GIS, nonparametric multiplicative regression (NPMR) habitat modeling, and
maximum entropy modeling (Maxent). Results indicate that oceanographic conditions
have the potential to influence Humboldt squid occurrence, and in Oregon, sightings
vary temporally and spatially. Combining the sightings from fishermen and scientific
surveys greatly enhanced the spatial extent of the data. Humboldt squid were most
frequently observed between 124.4��W and 125��W in proximity to the shelf-break at
the 200 m isobath, with peak sightings (116) recorded in 2009 and the fewest (6)
reported in 2003 and 2011. The highest occurrence of Humboldt squid were observed
at a SST of 10.5-13.0��C, 0.26-3.0 mg m����� chla content, -4.0-1.0 m SSH anomalies,
32.2-32.8 psu SSS, and at 3-4.5 ml L����� and 6-7 ml L����� 30 m depth DO. Maps of
estimated likelihood of occurrence generated by NPMR were consistent with
overlayed observations from fishermen, which were not used in the model because
they were limited to presence-only information.
An interdisciplinary approach that incorporates cooperative fisheries research
and ecosystem-based management is necessary for monitoring Humboldt squid in
Oregon. Traditional methods are insufficient because Humboldt squid are data-poor,
highly migratory, and are main predators of many commercially important fisheries in
Oregon. Based on my findings, sightings recorded by fishermen covered a much
larger area over a longer time frame than the scientific survey and observer data, and
excluding their knowledge would have led to a different interpretation of Humboldt
squid distribution and environmental tolerances. Although there is uncertainty in the
data from potential map bias or misidentification of smaller Humboldt squid,
incorporating sightings from fishermen with traditional fisheries research increases the
quantity and quality of information. Cooperative monitoring for Humboldt squid
could include training in species identification and sea condition reporting in
logbooks. Future "invasions" are likely, and more eyes on the water will improve our
understanding of the behavior and impacts of Humboldt squid on coastal resources. / Graduation date: 2013
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35855 |
| Date | 04 September 2012 |
| Creators | Chesney, Tanya A. |
| Contributors | Heppell, Selina S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Relation | Oregon Explorer |
Page generated in 0.0021 seconds