Biomass Of Cephalopods Research Articles

Biomass and trait biogeography of cephalopods on the European and North American continental shelves

AbstractAimWe evaluate whether the biomass and trait biogeography of cephalopods follow the distribution expected by metabolic theory for ectotherms with rapid growth and high metabolic rate.LocationContinental shelves of the North Atlantic and Northeast Pacific oceans; global marine ecoregions.Time Period1968–2020.Major Taxa StudiedCephalopods and fishes (Chondrichthyes and Osteichthyes).MethodsWe map the biomass of cephalopods and their traits across marine shelves using scientific bottom trawl survey data from the North Atlantic and Northeast Pacific. We further map global fisheries catch. We apply statistical methods to evaluate how temperature, zooplankton productivity and depth drive these patterns.ResultsCephalopods represent a small fraction (1%) of the combined fish and cephalopod biomass on continental shelves. However, their distribution displays a high regional heterogeneity, with some areas being virtually absent of cephalopods and other areas accounting for up to 24% of total biomass. Higher temperatures and zooplankton productivity are associated with increased cephalopod biomass and proportional biomass relative to fish. The largest cephalopods are found in the Northeast Pacific. Growth rates are highest in warmer waters with fastest growth rates found in lower latitudes of the North Atlantic. Cephalopods constitute 5% of the combined fish and cephalopod global fisheries catch. This proportion varies across regions. Higher temperature and zooplankton productivity are associated with increased cephalopod catch relative to fish.Main ConclusionsTemperature and productivity shape the large‐scale biogeography of cephalopods and their traits on marine shelves. The relations with temperature suggest that future warming could lead to a proliferation of fast‐growing cephalopods in cold and temperate systems, with implications for ecosystem dynamics and fisheries. Despite a relatively low observed biomass, cephalopods hold substantial potential to change ecosystem structure and functioning given their high energy lifestyle.

Trophodynamics of the eastern Great Australian Bight ecosystem: Ecological change associated with the growth of Australia's largest fishery

We used the Ecopath with Ecosim software to develop a trophic mass-balance model of the eastern Great Australian Bight ecosystem, off southern Australia. Results provide an ecosystem perspective of Australia's largest fishery, the South Australian sardine fishery, by placing its establishment and growth in the context of other dynamic changes in the ecosystem, including: the development of other fisheries; changing abundances of apex predator populations and oceanographic change. We investigated the potential impacts of the sardine fishery on high tropic level predators, particularly land-breeding seals and seabirds which may be suitable ecological performance indicators of ecosystem health. Results indicate that despite the rapid growth of the sardine fishery since 1991, there has likely been a negligible fishery impact on other modelled groups, suggesting that current levels of fishing effort are not impacting negatively on the broader ecosystem structure and function in the eastern Great Australian Bight. Results highlight the importance of small pelagic fish to higher trophic levels, the trophic changes that have resulted from loss and recovery of apex predator populations, and the potential pivotal role of cephalopod biomass in regulating ‘bottom-up’ trophic processes. The ability to resolve and attribute potential impacts from multiple fisheries, other human impacts and ecological change in this poorly understood region is highlighted by the study, and will be critical to ensure future ecologically sustainable development within the region.

Predation on cephalopods by Weddell seals, Leptonychotes weddellii, at Hope Bay, Antarctic Peninsula

Cephalopods play a key role in marine environments as food resources for top predators such as marine mammals and seabirds. However, detailed information on their trophic relationships with Antarctic seals is scarce. The aim of the present study was to examine the cephalopod portion of the diet of adult and subadult Weddell seals, Leptonychotes weddellii, at Hope Bay, Antarctic Peninsula, through the analysis of scats collected during three consecutive summers (2003, 2004 and 2005). Cephalopods occurred in almost 45% of the 217 samples collected during the whole period of study. A total of 662 beaks (358 upper and 304 lower) were removed from scats containing cephalopod remains (n = 93). Octopods were largely dominant in comparison with teuthoids constituting in numerical abundance over 95% of the cephalopod prey. The octopod Pareledone turqueti was the most frequent and dominant prey species representing, respectively, 57.9 and 71.1% in numbers and biomass of cephalopods consumed. Species belonging to the group of papillated Pareledone were second in importance. The results were compared with information from previous dietary studies of L. weddellii at other localities of Antarctica. Based on the examination of the cephalopod prey taxa identified in this study, it is suggested that during the study period Weddell seal individuals foraged mainly on benthic prey resources close to the coast, in inshore waters where octopods were dominant in comparison with pelagic squid.

Pelagic cephalopods from eastern Australia: species composition, horizontal and vertical distribution determined from the diets of pelagic fishes

The distribution and relative biomass of cephalopods from pelagic waters off eastern Australia was examined between 1997 and 2004 from stomach contents of swordfish, yellowfin tuna and dolphinfish taken in the domestic longline fishery. A total of 38 taxa from 19 families were identified. Comparison of the species composition of the three predators indicated pronounced differences in cephalopod species composition. In swordfish, species of the family Ommastrephidae, particularly Ommastrephes bartramii (Lesueur 1821) and Nototodarus gouldi (McCoy 1888) dominated, whereas a more diverse mix of species was identified from yellowfin-sampled cephalopods. Todaropsis eblanae (Ball 1841) was the main cephalopod sampled from the surface-dwelling dolphinfish. For swordfish-sampled cephalopods, significant relationships were found between biomass and season, fluorescence and year. In yellowfin tuna, cephalopod biomass was significantly correlated with season, area and sea surface temperature. Significant factors differed between predator-sampler, possibly reflecting the limits of the predator, but could also give insights into individual cephalopod species distributions. However, the increase in cephalopod biomass over summer in both swordfish and yellowfin tuna suggested cephalopod biomass was higher over summer in the region.

Cephalopod growth: historical context and future directions

Research into the biology and management of cephalopods continues to accelerate rapidly. This has been especially so in the past decade. The discovery of new and bizarre species (Vecchione et al. 2001), the advancement of large-scale studies based on geographic information systems (GIS; Waluda et al. 2001), the use of new technology to track individuals and study activity in situ (O’Dor et al. 2002), the challenges of managing growing cephalopod fisheries (Lipinski et al. 1998), the patterns of growth at a cellular level (Semmens and Moltschaniwskyj 2000), the physiological constraints on life spans (Zielinski and Portner 2000) and the potential use of individuals as ecosystem indicators (Jackson and Domeier 2003) are all examples of advances in this field in recent years. Furthermore, understanding and describing cephalopod growth continues to pose challenges and difficulties. While ageing structures in squid, such as, statoliths and gladii to some extent, have proven to be valuable tools for deciphering and describing growth, we are still facing challenges with other groups, such as, cuttlefish and octopus. Even when ageing data are available and we can construct size-at-age plots, this does not necessarily reveal the form of growth. Individual growth rates can be so plastic that attempting to fit curves to such scatter plots is not straightforward or helpful. In the context of these challenges, a workshop was convened on cephalopod growth and held in association with the 2003 Cephalopod InternationalAdvisory Council (CIAC) symposium on the island of Phuket in Thailand. The purpose of this workshop was to bring together experts from around the world, to review and evaluate the current state of knowledge, to work on techniques to advance the field and to provide direction for the future. This special issue is a direct, but independently derived, result of that workshop and attempts to provide a synthesis of our current knowledge and to provide stimulus for future work. Why attempt to understand the growth of cephalopods? Is it really that important? The significance of cephalopods in the world’s oceans can be appreciated by the trend of increasing cephalopod catches worldwide, which is in marked contrast to traditional finfish fisheries (Caddy and Rodhouse 1998). Perhaps a more satisfying rationale for studying the dynamics of cephalopod populations has been given by Clarke (1983) who has estimated that sperm whales alone consume >100 million tonnes of squid annually and that this figure probably exceeds half of the biomass of humanity. If this is the estimate of just squids eaten by all individuals of only one predator, the total biomass of cephalopods in the world’s oceans must greatly exceed that of humans. Thus, a better knowledge of their growth and dynamics will help to assist us in understanding an important component of the world marine ecosystem. This special issue provides broad-scale review and discussion papers as well as specific data papers, all related to issues of cephalopod growth. The majority of work in cephalopod age and growth has been focused on both the near-shore myopsid and offshore oegopsid squid. Hence, Jackson (2004, myopsid squid) andArkhipkin (2004, oegopsid squid) present timely reviews in this issue. These reviews argue that there is considerable scope for further research on statolith ageing techniques, as many species have not yet been studied in any detail. They also suggest that stringency in statolith ageing techniques needs to be maintained and call for an expansion of increment periodicity studies. There are greater challenges studying age and growth of octopus because there are no standard ageing techniques. Semmens et al. (2004) review the history and challenges in studying octopus growth, and highlight the need to develop and expand novel techniques for ageing octopus. Cuttlefish are also an important, widespread and challenging group to study in terms of age and growth, and deserve further attention. Moltschaniwskyj (2004) takes a novel approach in reference to the history and overview of cephalopod growth at a variety of biological scales, including relative growth of organs, muscle fibres, proximal composition and protein synthesis. Examining these processes has helped explain how cephalopods fuel their rapid growth and life histories, although different measurements will provide information on different time scales. Moltschaniwskyj (2004) points out that protein synthesis can provide information on the

Predicting indirect effects of fishing in Mediterranean rocky littoral communities using a dynamic simulation model

Modelling may significantly enhance our understanding of the potential impacts of fisheries at larger spatial scales and on groups that would otherwise be very difficult to study. An aggregated biomass-based simulation model of a Mediterranean infralittoral zone was developed and used to carry out fishing ‘experiments’ where fishing intensity and catch selection were varied. The model was constructed for the Bay of Calvi, Corsica, using the Ecopath with Ecosim software, and was composed of 27 compartments, including seabirds, 11 groups of fish, 12 groups of invertebrates, 2 primary producers, bacteria and detritus. Several instances of indirect fishing effects (‘trophic cascades’ and ‘keystone predation’) have been proposed from anecdotal evidence in the western Mediterranean. Model outcomes provided little support for the widely accepted paradigm that fishing, by removing invertebrate-feeding fish, allows increases in the biomass of sea urchins and as a consequence the formation of overgrazed ‘barrens’ of bare substrate. Simulated harvesting of sea urchins by humans did, however, results in an increase of macroalgal biomass as reported previously. Intensified fishing pressure on ‘macrocarnivorous’ fish resulted in a ‘release’ of small fish species (e.g. blennies), and as a consequence a decline in the biomass of some small invertebrates on which they feed (e.g. amphipods). Increased fishing on large ‘piscivores’ resulted in increases in other small fish groups and consequential effects on other benthic invertebrate groups (e.g. polychaetes). Depletion of piscivorous fish resulted in a dramatic increase in the biomass of seabirds, which apparently compete with piscivores for small demersal and pelagic fish. An intensification of fishing pressure overall resulted in an increase in cephalopod biomass. Responses of target species to increased fishing pressure were most marked within the first 5 years of the new fishing regime. Indirect responses exhibited varying degrees of inertia, and biomasses of many groups did not assume a new equilibrium within the first 20 years of the simulation. The Mediterranean infralittoral rocky-bottom ecosystem was predicted to be relatively resilient to pulses of increased fishing and exhibited a high degree of detritus recycling. However, the speed and magnitude of ecosystem responses was shown to depend greatly on the extent of ‘top-down’ or ‘bottom-up’ control assumed for components within the system.

DIFFERENCES IN NICHE BREADTH AMONG SOME TEUTHIVOROUS MESOPELAGIC MARINE MAMMALS

Marine Mammal ScienceVolume 19, Issue 2 p. 400-406 DIFFERENCES IN NICHE BREADTH AMONG SOME TEUTHIVOROUS MESOPELAGIC MARINE MAMMALS Hal Whitehead, Hal Whitehead Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada and Max Planck Institute for Behavioural Physiology, Seewiesen, D-82305 Germany E-mail: [email protected]Search for more papers by this authorColin D. MacLeod, Colin D. MacLeod Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, United Kingdom and Beaked Whale Research Project, Lower Right, 59 Jute Street, Aberdeen AB24 3EX, United KingdomSearch for more papers by this authorPaul Rodhouse, Paul Rodhouse British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge CB3 0ET, United KingdomSearch for more papers by this author Hal Whitehead, Hal Whitehead Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada and Max Planck Institute for Behavioural Physiology, Seewiesen, D-82305 Germany E-mail: [email protected]Search for more papers by this authorColin D. MacLeod, Colin D. MacLeod Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, United Kingdom and Beaked Whale Research Project, Lower Right, 59 Jute Street, Aberdeen AB24 3EX, United KingdomSearch for more papers by this authorPaul Rodhouse, Paul Rodhouse British Antarctic Survey, Natural Environment Research Council, Madingley Road, Cambridge CB3 0ET, United KingdomSearch for more papers by this author First published: 26 August 2006 https://doi.org/10.1111/j.1748-7692.2003.tb01118.xCitations: 29AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume19, Issue2April 2003Pages 400-406 RelatedInformation

Cephalopods eaten by wandering albatrosses (Diomedea exulansL.) breeding at six circumpolar localities

Abstract The beaks of 9,994 cephalopods of 61 species, obtained mainly from chick regurgitations of wandering albatrosses (Diomedea exulans L.) at Gough, Auckland, Antipodes, Prince Edward and Macquarie Islands and South Georgia, were used to specify and calculate the biomass of cephalopods consumed. Histioteuthidae were most important by numbers and biomass at Gough Island (in warmest seas), but Onycboteuthidae increasingly superseded them southwards; Kondakovia longimana formed 59 to 75% of biomass eaten at the three localities nearest the Antarctic Polar Front. Other important families were Octopoteuthidae, Cranchiidae, Architeuthidae (juveniles) and Ommastrephidae (South Georgia only). Most frequently eaten were Histioteuthis atlantica 13.7%, Galiteuthis glacialis 12.4%, H. eltaninae 12.0% and Kondakovia longimana 11.6%. Wandering albatrosses rearing chicks can forage at least to 3,000 km in a single foray, and may exploit an important food source about 1200 km from the nest (as in the probable commensalism of South Georgian birds with the Falkland Islands fishery). They feed, sometimes opportunistically, on cephalopods active or moribund at the surface, or discarded or lost by trawlers, cetaceans or seals. Vertically migrating cephalopods, especially bioluminescent species, are disproportionately frequent in their non-commensal diet, suggesting that they often feed at night.

Cephalopod biomass – estimates from predation

North Atlantic deep sea cephalopods caught in research nets (mouth opening of9 m2) and I arge commercial trawls are compared with those eaten by Sperm Whales. 1t is shown that at three latitudes the nets and whales sample cephalopods very differently. Research nets are biased towards collecting small species and young specimens of several families, principally gonatids, cranchiids, enoploteuthids and onychoteuthids, while sperm whales are biased towards catching much !arger cephalopods, particularly histioteuthids. Commercial trawls tend to bridge the gap in size of cephalopods selected by research nets and whales but where comparisons are possible they have a bias towards catching enoploteuthids. The contribution by numbers and weight of different cephalopod families to the cephalopod fraction of the diet of sperm whales throughout the world is reviewed. A detailed study of Antarctic cephalopods in the diet of large predators including cetaceans, seals and birds indicates areas where more knowledge is required to make accurate estimates of the biomass of Antarctic cephalopods consumed. The value of direct studies of food webs for quantitative consideration of particular cephalopod taxa is demonstrated and discussed.