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- Nov 19, 2002
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We are reaching that time of the year, the beginning of the new calendar year, when students might be looking for possible research topics in marine science. I've attached an outline for one research topic that I would dearly like someone to work on. If you are interested in undertaking this research please contact me directly at [email protected]
We have actually commenced processing and identifying the contents of the cetacean stomachs referred to below, but much remains to be done (and further samples will be collected in subsequent strandings) even if we complete identifications and measurements on existing samples (this really is just the first stage of research).
Thanks
Steve
Subject: "The composition of cephalopods in toothed-whale diet in New Zealand waters"
Rationale
Cephalopods (octopus and squid) are significant in the marine food web, comprising a major portion of the diet of many apex predators such as marine mammals (cetaceans and pinnipeds), seabirds and large fish (both teleosts and elasmobranchs) (Clarke 1996a, b). However, the systematics of many cephalopod species require considerable revision, exceedingly little is known of the biology of many species, and we are only now beginning to appreciate the true bathymetric, geographic and ontogenetic distribution of some select species.
The diet of several toothed whale species found around New Zealand is predominantly squid (e.g. pygmy sperm whales Kogia breviceps, Risso’s dolphin, Grampus griseus; long-finned pilot whale, Globicephala melas and sperm whales Physeter macrocephalus, and the majority of beaked-whale species [family Ziphidae]: MacLeod et al. 2003, Barros & Clarke 2002, Clarke 1996b). Worldwide, compared to fish-eating species, little is known about the diet of cephalopod-eating whales, due largely to the inherent difficulties of studying their feeding ecology. The most frequently used technique entails examination of stomach contents of dead animals (Barros & Clarke 2002).
Quite remarkably, given the unusually high number of stranded individuals of cephalopod-eating cetaceans in New Zealand waters (Tuohy et al. 2001, Brabyn 1991, Dalebout 2002), their diet is poorly known (Gaskin & Cawthorn 1967a, b [sperm whales harpooned in Cook Strait]; Clarke & MacLeod 1982 [sperm whales harpooned in the Tasman Sea]; Clarke & Roper 1998 [one sperm whale stranded at Paikakariki]). The pygmy sperm whale, K. breviceps, is considered an opportunistic feeder, with up to 77 different prey species identified from stomach contents from South African specimens (including 55 cephalopod taxa; Plön et al. 1999). More remarkably, although New Zealand appears to have the second highest number of strandings worldwide for pygmy sperm whales (after Florida), no regional dietary information is available for this species (data on their diet is known for Florida (Candela 1987, abstract), South Africa (Ross 1979) and Taiwan (Wang et al. 2002)).
Some 132 cephalopod taxa are now recognised from New Zealand waters (O’Shea unpublished). Despite this diversity there is a dearth of biological information on any species, although some, described as recently as 1999, already appear to be threatened as a consequence of fishing activity (based on rates of decline [to total absence] in abundance in fisheries bycatch). Five large-bodied cephalopod species are presently recognised as threatened or endangered in the DOC ‘Threat Classification System’ (Hitchmough 2002) - each as a consequence of deep-sea bottom-trawling: Cirroctopus hochbergi, Opisthoteuthis mero, O. chathamensis, Octopus kaharoa, and Idioteuthis cordiformis. Other large-bodied squid not listed in this classification, for which concern is here expressed, are: Taningia danae, Taningia sp. nov., Octopoteuthis sp. nov. (giant), Lepidoteuthis grimaldii, Pholidoteuthis boschmai, Architeuthis dux, any of 7 locally occurring species of Histioteuthis, and any of three species of Moroteuthis. Two of the former, Opisthoteuthis mero and Idioteuthis cordiformis, and all of the latter are either a significant part of or component in the diet of sperm whales (P. macrocephalus).
Trawling is the most pervasive of man’s marine activities to depths of 1200 m (Cryer et al. 2002) - a depth to which sperm whales regularly dive. As many squid and octopus are trawled as fisheries bycatch, and discarded dead at sea, and as a sperm whale can consume 800-1000 squid per day (Clarke 1980), it follows that any change in either the size-class composition or diversity of cephalopod fauna will be manifested in the diet of the whale; similarly, any change in abundance of squid will be manifested in the diet of the whale (number of beaks in the stomachs). The diversity, size-class structure and abundance of squid can effectively act as environmental barometers, providing an index of environmental health from a whale’s perspective.
With the apparent decrease in both abundance and diversity of large-bodied cephalopod species in our waters, and the effective collapse of orange roughy stocks (reported from the stomachs of sperm whales by Gaskin & Cawthorn (1967a)), it is likely that the diet of toothed whales, particularly sperm whales, has changed already, and worse still, has been forced to change as a direct consequence of deep-sea trawling (fish comprised 37% by weight in the diet of sperm whales reported by Gaskin & Cawthorn, loc. cit.). If unregulated, the long-term repercussions of deep-sea trawling to cephalopod-eating cetaceans and pinnipeds could be devastating. Basically, the theory is 'destroy the environment, kill the squid (and everything else), and lose the whales'.
The specific aims of this proposed research would be to:
Conduct an opportunistic survey of the diet of toothed whales from New Zealand, based on existing/archived stomach content samples.
Determine whether any temporal shift in cetacean diet is apparent, based on existing/archived stomach content samples and historical literature accounts.
Establish a nationwide network to receive stomach contents from stranded cetaceans and pinnipeds, and also, where possible, seabirds and large fish (both teleosts and elasmobranchs).
Suggested methodology:
Locate and acquire all archived stomach contents samples available in New Zealand (for instance, 26 K. breviceps and 11 P. macrocephalus unprocessed stomach-content samples have been archived to date).
Process, sort and store samples in accordance with modern curatorial standards. Identify cephalopod remains by examination of representative taxa from voucher collections, recognising them as occurring within New Zealand waters in accordance with O’Shea (1997), and identifying them in accordance to guides to lower-beak identification (Clarke 1986). A guide to upper beaks could also be compiled in the process.
Envisaged outputs:
An excellent, applied Masters thesis.
A greater understanding of the diet of the toothed whales in New Zealand waters, especially the sperm whale (P. macrocephalus) and pygmy sperm whale (K. breviceps), and the first detailed reports of other regionally occurring cephalopod-eating cetacean and pinniped species.
At least three publications:
1. A description and review of the diet of toothed whale species from New Zealand, based on stomach content analysis of archived samples, for both Kogia and Physeter (refereed journal).
2. Comparison of historical and contemporary data on the diet of cephalopod-eating whales, particularly the sperm whale: an appraisal of anthropogenic threats to species (refereed journal).
3. A simplified review of the diet of toothed whale species from New Zealand, based on stomach content analysis of archived samples, in conjunction with an overview of anthropogenic threats to species (popular article, non-refereed)
With the New Zealand octopus fauna now fully revised (O’Shea 1999), and the squid fauna in the process of revision (O’Shea in prep), much former cephalopod identification based on beaks will require amendment (as both the diversity and novelty of Southern Ocean and New Zealand cephalopod taxa are more fully appreciated). This study (of cephalopod-eating whale stomach contents) will contribute invaluable data to a monographic review of the New Zealand (and southern ocean) cephalopod fauna.
References at end of post
We have actually commenced processing and identifying the contents of the cetacean stomachs referred to below, but much remains to be done (and further samples will be collected in subsequent strandings) even if we complete identifications and measurements on existing samples (this really is just the first stage of research).
Thanks
Steve
Subject: "The composition of cephalopods in toothed-whale diet in New Zealand waters"
Rationale
Cephalopods (octopus and squid) are significant in the marine food web, comprising a major portion of the diet of many apex predators such as marine mammals (cetaceans and pinnipeds), seabirds and large fish (both teleosts and elasmobranchs) (Clarke 1996a, b). However, the systematics of many cephalopod species require considerable revision, exceedingly little is known of the biology of many species, and we are only now beginning to appreciate the true bathymetric, geographic and ontogenetic distribution of some select species.
The diet of several toothed whale species found around New Zealand is predominantly squid (e.g. pygmy sperm whales Kogia breviceps, Risso’s dolphin, Grampus griseus; long-finned pilot whale, Globicephala melas and sperm whales Physeter macrocephalus, and the majority of beaked-whale species [family Ziphidae]: MacLeod et al. 2003, Barros & Clarke 2002, Clarke 1996b). Worldwide, compared to fish-eating species, little is known about the diet of cephalopod-eating whales, due largely to the inherent difficulties of studying their feeding ecology. The most frequently used technique entails examination of stomach contents of dead animals (Barros & Clarke 2002).
Quite remarkably, given the unusually high number of stranded individuals of cephalopod-eating cetaceans in New Zealand waters (Tuohy et al. 2001, Brabyn 1991, Dalebout 2002), their diet is poorly known (Gaskin & Cawthorn 1967a, b [sperm whales harpooned in Cook Strait]; Clarke & MacLeod 1982 [sperm whales harpooned in the Tasman Sea]; Clarke & Roper 1998 [one sperm whale stranded at Paikakariki]). The pygmy sperm whale, K. breviceps, is considered an opportunistic feeder, with up to 77 different prey species identified from stomach contents from South African specimens (including 55 cephalopod taxa; Plön et al. 1999). More remarkably, although New Zealand appears to have the second highest number of strandings worldwide for pygmy sperm whales (after Florida), no regional dietary information is available for this species (data on their diet is known for Florida (Candela 1987, abstract), South Africa (Ross 1979) and Taiwan (Wang et al. 2002)).
Some 132 cephalopod taxa are now recognised from New Zealand waters (O’Shea unpublished). Despite this diversity there is a dearth of biological information on any species, although some, described as recently as 1999, already appear to be threatened as a consequence of fishing activity (based on rates of decline [to total absence] in abundance in fisheries bycatch). Five large-bodied cephalopod species are presently recognised as threatened or endangered in the DOC ‘Threat Classification System’ (Hitchmough 2002) - each as a consequence of deep-sea bottom-trawling: Cirroctopus hochbergi, Opisthoteuthis mero, O. chathamensis, Octopus kaharoa, and Idioteuthis cordiformis. Other large-bodied squid not listed in this classification, for which concern is here expressed, are: Taningia danae, Taningia sp. nov., Octopoteuthis sp. nov. (giant), Lepidoteuthis grimaldii, Pholidoteuthis boschmai, Architeuthis dux, any of 7 locally occurring species of Histioteuthis, and any of three species of Moroteuthis. Two of the former, Opisthoteuthis mero and Idioteuthis cordiformis, and all of the latter are either a significant part of or component in the diet of sperm whales (P. macrocephalus).
Trawling is the most pervasive of man’s marine activities to depths of 1200 m (Cryer et al. 2002) - a depth to which sperm whales regularly dive. As many squid and octopus are trawled as fisheries bycatch, and discarded dead at sea, and as a sperm whale can consume 800-1000 squid per day (Clarke 1980), it follows that any change in either the size-class composition or diversity of cephalopod fauna will be manifested in the diet of the whale; similarly, any change in abundance of squid will be manifested in the diet of the whale (number of beaks in the stomachs). The diversity, size-class structure and abundance of squid can effectively act as environmental barometers, providing an index of environmental health from a whale’s perspective.
With the apparent decrease in both abundance and diversity of large-bodied cephalopod species in our waters, and the effective collapse of orange roughy stocks (reported from the stomachs of sperm whales by Gaskin & Cawthorn (1967a)), it is likely that the diet of toothed whales, particularly sperm whales, has changed already, and worse still, has been forced to change as a direct consequence of deep-sea trawling (fish comprised 37% by weight in the diet of sperm whales reported by Gaskin & Cawthorn, loc. cit.). If unregulated, the long-term repercussions of deep-sea trawling to cephalopod-eating cetaceans and pinnipeds could be devastating. Basically, the theory is 'destroy the environment, kill the squid (and everything else), and lose the whales'.
The specific aims of this proposed research would be to:
Conduct an opportunistic survey of the diet of toothed whales from New Zealand, based on existing/archived stomach content samples.
Determine whether any temporal shift in cetacean diet is apparent, based on existing/archived stomach content samples and historical literature accounts.
Establish a nationwide network to receive stomach contents from stranded cetaceans and pinnipeds, and also, where possible, seabirds and large fish (both teleosts and elasmobranchs).
Suggested methodology:
Locate and acquire all archived stomach contents samples available in New Zealand (for instance, 26 K. breviceps and 11 P. macrocephalus unprocessed stomach-content samples have been archived to date).
Process, sort and store samples in accordance with modern curatorial standards. Identify cephalopod remains by examination of representative taxa from voucher collections, recognising them as occurring within New Zealand waters in accordance with O’Shea (1997), and identifying them in accordance to guides to lower-beak identification (Clarke 1986). A guide to upper beaks could also be compiled in the process.
Envisaged outputs:
An excellent, applied Masters thesis.
A greater understanding of the diet of the toothed whales in New Zealand waters, especially the sperm whale (P. macrocephalus) and pygmy sperm whale (K. breviceps), and the first detailed reports of other regionally occurring cephalopod-eating cetacean and pinniped species.
At least three publications:
1. A description and review of the diet of toothed whale species from New Zealand, based on stomach content analysis of archived samples, for both Kogia and Physeter (refereed journal).
2. Comparison of historical and contemporary data on the diet of cephalopod-eating whales, particularly the sperm whale: an appraisal of anthropogenic threats to species (refereed journal).
3. A simplified review of the diet of toothed whale species from New Zealand, based on stomach content analysis of archived samples, in conjunction with an overview of anthropogenic threats to species (popular article, non-refereed)
With the New Zealand octopus fauna now fully revised (O’Shea 1999), and the squid fauna in the process of revision (O’Shea in prep), much former cephalopod identification based on beaks will require amendment (as both the diversity and novelty of Southern Ocean and New Zealand cephalopod taxa are more fully appreciated). This study (of cephalopod-eating whale stomach contents) will contribute invaluable data to a monographic review of the New Zealand (and southern ocean) cephalopod fauna.
References at end of post
yet 
