Trends in Cephalopod Populations

DWhatley

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A number of new studies citing climate change and fishing as making changes to the abundance and location of cephalopod populations are beginning show up in current publications. This thread is an attempt to collect the articles for review.
 
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DWhatley

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Can fishing pressure invert the outcome of interspecific competition? The case of the thiof and of the octopus along the Senegalese coast
Thuy Nguyen-Phuong, Doanh Nguyen-Ngoc, Pierre Auger. Sidy Ly. Didier Jouffre 2015 (pdf)

Abstract We present a mathematical model of two competing marine species that are harvested. We consider three models according to different levels of complexity, without and with species refuge and density-independent and density-dependent species movement between fishing area and refuge. We particularly study the effects of the fishing pressure on the outcome of the competition. We focus on conditions that allow an inferior competitor to invade as a result of fishing pressure. The model is discussed in relationship to the case of the thiof and the octopus along the Atlantic West African coast. At the origin, the thiof was abundant and the octopus scarce in that region. Since, the fishing pressure has strongly increased in some fishing areas leading to the depletion of the thiof and the invasion of its competitor, the octopus.
 

DWhatley

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Recognizing cephalopod boreholes in shells and the northward spread of Octopus vulgaris Cuvier, 1797 (Cephalopoda, Octopodoidea)
Auke-Florian HIEMSTRA 2015 full article.

ABSTRACT Octopuses prey on molluscs by boring through their shell. Among the regular naticid borings, traces of cephalopod predation should be found soon on Dutch beaches. Bottom trawling has declined, and by the effects of global warming Octopus will find its way back to the North Sea where it lived before. I describe the distinguishing characters for Octopus bore holes, give an introduction into this type of behaviour, present a short history of Dutch octopuses and a prediction of their future.
 

DWhatley

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Large-scale spatio-temporal patterns of Mediterranean cephalopod diversity
Keller Stefanie,Bartolino Valerio, Hidalgo Manuel, Bitetto Isabella, Casciaro Loredana, Cuccu Danila, Esteban Antonio, Garcia Cristina, Garofalo Germana, Josephides Marios, Jadaud Angelique, Lefkaditou Evgenia, Maiorano Porzia, Manfredi Chiara, Marceta Bojan, Massuti Enric, Micallef Reno, Peristeraki Panagiota, Relini Giulio, Sartor Paolo, Spedicato Maria Teresa, Tserpes George, Quetglas Antoni 2015 (pdf)

Abstract : Species diversity is widely recognized as an important trait of ecosystems’ functioning and resilience. Understanding the causes of diversity patterns and their interaction with the environmental conditions is essential in order to effectively assess and preserve existing diversity. While diversity patterns of most recurrent groups such as fish are commonly studied, other important taxa such as cephalopods have received less attention. In this work we present spatio-temporal trends of cephalopod diversity across the entire Mediterranean Sea during the last 19 years, analysing data from the annual bottom trawl survey MEDITS conducted by 5 different Mediterranean countries using standardized gears and sampling protocols. The influence of local and regional environmental variability in different Mediterranean regions is analysed applying generalized additive models, using species richness and 2 Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. the Shannon Wiener index as diversity descriptors. While the western basin showed a high diversity, our analyses do not support a steady eastward decrease of diversity as proposed in some previous studies. Instead, high Shannon diversity was also found in the Adriatic and Aegean Seas, and high species richness in the eastern Ionian Sea. Overall diversity did not show any consistent trend over the last two decades. Except in the Adriatic Sea, diversity showed a hump-shaped trend with depth in all regions, being highest between 200-400 m depth. Our results indicate that high Chlorophyll a concentrations and warmer temperatures seem to enhance species diversity, and the influence of these parameters is stronger for richness than for Shannon diversity.
 

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