Yellowfin Tuna Thunnus Albacares Research Articles

Improvement of Water Chemistry with Bacillus Probiotics Inclusion during Simulated Transport of Yellowfin Tuna Yolk Sac Larvae

AbstractThe effects of adding a probiotic Bacillus spp. blend on shipping bag water quality and survival of yolk sac larvae of yellowfin tuna Thunnus albacares during a 24‐h mock shipment were investigated. To better detect effects on water quality, the trial was designed without the utilization of available chemical water quality or temperature modulators. Shipping water salinity (30.7–31.0‰) and temperature (24.0–26.7°C) reflected conditions utilized during larval rearing. Probiotic incorporation (15 mL/L, about 1.5 × 106 colony‐forming units/mL) resulted in significantly lower final concentrations of total ammonia nitrogen and un‐ionized ammonia in comparison with the control. Significantly higher final mean dissolved oxygen concentration observed in the probiotic treatment could have resulted from stress reduction. Although no statistical difference was detected in larval survival upon termination of the trial, improvements in water quality (reduced total ammonia nitrogen and increased dissolved oxygen) resulting from incorporation of Bacillus probiotics would yield added levels of safety during shipping and would reduce the chances of negative results while incurring minimal increases in shipping costs.Received January 28, 2010; accepted May 1, 2010

Artisanal fisheries in La Paz Bay and adjacent oceanic area (Gulf of California, Mexico)

We analyzed the artisanal fishery capture data for La Paz Bay (Baja California Sur, Mexico) from 1998 to 2005. Capture data were related to the reproductive cycle of each species. Complete fishing records for 18 species of commercial importance belonging to eight families were identified. The most frequently captured species in La Paz Bay was the Pacific red snapper Lutjanus peru, with 43% of the total capture. This species was followed in importance by the spotted rose snapper Lutjanus guttatus, other groupers (Serranidae), and the jacks (Carangidae), with 18.8%, 15%, and 7.3% of the capture, respectively. Other commercial species captured in smaller amounts included the yellowfin tuna Thunnus albacares, the California flounder (or California halibut) Paralichthys californicus, the flathead mullet Mugil cephalus, the goliath grouper Epinephelus itajara, and different species of mojarra (Gerreidae). With few exceptions, catches outside the bay were higher than in the inner bay. All species were caught throughout the year regardless of their reproductive season. We recommend the implementation of fishery regulations for La Paz Bay, especially in the case of the Pacific red snapper, since it is the most exploited. Currently, overexploitation and possible local shortage of species may occur at any time and without warning in the near future. Aside from fishery management, an attractive option for increasing the supply of marine resources in the area is to use the inner bay for marine fish farming.

Feeding Ecology of Blue Marlins, Dolphinfish, Yellowfin Tuna, and Wahoos from the North Atlantic Ocean and Comparisons with other Oceans

AbstractWe examined diet, dietary niche width, diet overlap, and prey size–predator size relationships of blue marlins Makaira nigricans, dolphinfish Coryphaena hippurus, yellowfin tuna Thunnus albacares, and wahoos Acanthocybium solandri caught in the western North Atlantic Ocean during the Big Rock Blue Marlin Tournament (BRT) in 1998–2000 and 2003–2009 and dolphinfish captured outside the BRT from 2002 to 2004. Scombrids were important prey of blue marlins, yellowfin tuna, and wahoos; other frequently consumed prey included cephalopods (for yellowfin tuna and wahoos) and exocoetids (for yellowfin tuna). Dolphinfish diets included exocoetids, portunids, and conspecifics as important prey. Blue marlins and wahoos consumed relatively few prey species (i.e., low dietary niche width), while dolphinfish had the highest dietary niche width; yellowfin tuna had intermediate niche width values. Maximum prey size increased with dolphinfish size; however, the consumption of small prey associated with algae Sargassum spp. occurred across the full size range of dolphinfish examined. Most interspecific diet overlap values with dolphinfish were not significant; however, blue marlins, yellowfin tuna, and wahoos had significant diet overlap due to their reliance on scombrid prey. Prey types found in blue marlins, dolphinfish, and wahoos were more consistent among BRT years than prey found in yellowfin tuna. The prey of yellowfin tuna and wahoos collected during BRT years correlated with historic (early 1980s) diet data from North Carolina, the Gulf of Mexico, and the Bahamas. Based on principal components analysis, diets from several oceans clustered together for blue marlins, dolphinfish, yellowfin tuna, and wahoos. Although differences were found, the diets of each predator were largely consistent both temporally (e.g., over the past three decades in the Gulf Stream) and spatially (among oceans), despite potential effects of fishing or environmental changes.

Fishery and feeding habits of yellowfin tuna (<i>Thunnus albacares</i>) targeted by coastal tuna longlining in the north western and north eastern coasts of Sri Lanka

Present study analyzed the catch, effort and size distribution of yellowfin tuna ( Thunnus albacares ) caught by coastal tuna longlining in north western and north eastern coastal waters of Sri Lanka from January 2005 to December 2006. Further, the contents of 83 non–empty stomachs were analyzed and the indices such as frequency of occurrence (%F), percentage of number of each food (%N), percentage of wet weight of each food item (%W) and percentage index of relative importance of each food item (%IRI) were calculated for the specimens caught from north western coastal waters from September 2006 to April 2007. Weekly fishery data were collected at major landing sites in north western and north eastern coastal areas. The fishing activities were carried out using Fiberglass Reinforced Boats (FRP) with outboard engine which basically operated in coastal waters during one day trip duration. The fishery was highly seasonal and it related to the monsoon pattern. Fishing started in October and continued until April of the following year in north western coast and from May to September in north eastern area. The estimated figure for total production in north western area (1052 t in 2005 and 3313 t in 2006) was higher than that in the north eastern area (578 t in 2005 and 741 t in 2006) and it was significant in 2006 (P Charybdis smithii followed by fishes belonging to family Sphyraenidae and Engraulididae. Loligo bartrami belonging to family Loliginidae, formed the main cephalopod prey. % IRI of crustaceans was higher than that of fish and cephalopods and this further revealed that the pelagic crab C. smithii is the most important prey item in the diet of yellowfin tuna. DOI: 10.4038/sljas.v13i0.2203 Sri Lanka J. Aquat. Sci. 13 (2008): 1-21

Modeling the spatial autocorrelation of pelagic fish abundance

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 411:203-213 (2010) - DOI: https://doi.org/10.3354/meps08667 Modeling the spatial autocorrelation of pelagic fish abundance Kristin M. Kleisner1,4,*, John F. Walter III2, Sandra L. Diamond3, David J. Die1 1Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA 2Southeast Fishery Science Center, NOAA, 75 Virginia Beach Drive, Miami, Florida 33149, USA 3School of Natural Sciences, University of Western Sydney, Locked Bag 1797, Penrith South DC, New South Wales 1797, Australia 4Present address: Fisheries Centre, University of British Columbia, 2202 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada *Email: k.kleisner@fisheries.ubc.ca ABSTRACT: The relationship between pelagic fish and ocean temperature is cited in many studies, the majority of which investigate correlations of pelagic species and sea surface temperatures (SST). While appropriate for surface-associated species, this may not be accurate for deep-diving fishes. A different way to examine this relationship is to model spatial autocorrelation of fish species and temperatures at an appropriate range of depths. Spatial autocorrelation, the distance at which data are interdependent, is a potential descriptor of the patch size of an organism. Here we modeled spatial autocorrelation for 5 pelagic species that inhabit different depths in the Gulf of Mexico: dolphinfish Coryphaena hippurus, wahoo Acanthocybium solandri, yellowfin tuna Thunnus albacares, swordfish Xiphias gladius, and bigeye tuna Thunnus obesus. Additionally, we modeled spatial autocorrelation for ocean temperatures at the surface, at 200, and 400 m. We hypothesized that autocorrelation distances will be greater for deeper water temperatures and for species that live at deeper depths due to greater homogeneity of deep waters over greater spatial ranges. Results show average distances of autocorrelation on the order of 55 to 60 km for wahoo and dolphinfish, 90 km for yellowfin tuna, and 135 to 145 km for swordfish and bigeye tuna; the same data for temperature were 75, 135, and 300 km for SST, and at 200 and 400 m depth, respectively. Autocorrelation distances of dolphinfish, wahoo, and yellowfin were correlated with that of of SST, while the autocorrelation distance of swordfish and bigeye were correlated with that of temperatures at 200 m. Results suggest that autocorrelation distances may be useful as a proxy for habitat delineation. KEY WORDS: Spatial analysis · Geostatistics · Variogram · Pelagic habitat · Dolphinfish · Bigeye tuna · Yellowfin tuna · Wahoo · Swordfish Full text in pdf format PreviousNextCite this article as: Kleisner KM, Walter JF III , Diamond SL, Die DJ (2010) Modeling the spatial autocorrelation of pelagic fish abundance. Mar Ecol Prog Ser 411:203-213. https://doi.org/10.3354/meps08667 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 411. Online publication date: July 29, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Efectos económicos y sociales del TLCAN en la pesca del atún en Baja California Sur, México

No obstante que el sistema internacional de comercio se desarrolló sin tomar en consideración un marco de protección ambiental, se han hecho esfuerzos para hacer coincidir objetivos ambientales y políticos. En México, Baja California Sur (BCS) es el estado más árido con la línea costera más extensa en el país (2,200 km). El objetivo de este trabajo fue identificar los impactos económicos y sociales que el Tratado de Libre Comercio para América del Norte (TLCAN) ha provocado en la pesca del atún aleta amarilla (thunnus albacares), en BCS. Analizamos la información más relevante para la pesca del atún en el periodo 1980-2000: crecimiento de la producción, incremento en la cantidad y valor de los productos exportados, número y antigüedad de las embarcaciones dedicadas a la captura del atún, incremento de la inversión en el sector pesquero dedicado al atún y la generación de empleos. Encontramos que en el corto y mediano plazo, el TLCAN no ha tenido efectos significativos sobre las variables económicas y sociales estudiadas para la pesca del atún. No es de esperar que la industria pesquera que participa en la captura del atún experimente cambios, positivos o negativos, en el punto de integración actual en que se encuentra el TLCAN.

Otoliths and vertebrae as potential hard structures for ageing South African yellowfin tuna Thunnus albacares

Sagittal otoliths and vertebrae from 46 yellowfin tuna Thunnus albacares (118-175 cm fork length) collected off the west coast of South Africa were assessed for potential usefulness in age estimation. Growth increments were found on both structures. Comparisons of growth increment counts showed that agreement in the counts of the number of growth increments was low (33-44%) but that most (90-94%) agreed to within one growth increment. Growth increment counts from whole otoliths, sectioned otoliths and vertebrae were not significantly different (f-test, p < 0.05). Among-reader precision was high for both whole otoliths (average percent error [APE] = 9.8%) and vertebrae (APE = 12.1%), but low for sectioned otoliths (APE = 34.9%). Age-bias plots indicated non-linear bias when sectioned otoliths were assessed in relation to other structures. Whole otoliths and whole vertebrae were considered equally precise, but the practicality of collecting vertebrae from the commercial fishery was better. Vertebrae are recommended as the most suitable structure for ageing yellowfin tuna.

Habitat and behaviour of yellowfin tuna Thunnus albacares in the Gulf of Mexico determined using pop‐up satellite archival tags

This study presents the first data on movement, habitat use and behaviour for yellowfin tuna Thunnus albacares in the Atlantic Basin. Six individuals were tracked in the Gulf of Mexico using pop-up satellite archival tags. Records up to 80 days in length were obtained, providing information on depth and temperature preferences as well as horizontal movements. Thunnus albacares in the Gulf of Mexico showed a strong preference for the mixed layer and thermocline, consistent with findings for this species in other ocean basins. Fish showed a diel pattern in depth distribution, remaining in surface and mixed layer waters at night and diving to deeper waters during the day. The vertical extent of T. albacares habitat appeared to be temperature limited, with fish generally avoiding waters that were >6 degrees C cooler than surface waters. The vertical and thermal habitat usage of T. albacares differs from that of bigeye Thunnus obesus and bluefin Thunnus thynnus, Thunnus orientalis and Thunnus maccoyii tunas. These results are consistent with the results of earlier studies conducted on T. albacares in other oceans.

Fishery and Biological Aspects of Yellowfin Tuna Thunnus albacares along Andhra Coast, India

A potentially rich fishing ground for yellowfin tuna Thunnus albacares discovered off northern Andhra Pradesh along the east coast of India at depths of 200m and more is being gainfully exploited by the local fishers since 2002. Hooks and lines as well as trolls operated mostly from non-mechanized crafts (catamaran) are the major exploitation methods used. The mechanized sector ventured into oceanic tuna fishing during 2006 with the conversion of a few existing mechanized trawlers into long liners and for large scale commercial exploitation of yellowfin tuna in this region. The average annual (2004-2006) landing of tuna by the catamaran at Visakhapatnam was 1,515t. A wide size group represented the fishery with the fork length of T.albacares measuring from 25 cm to 190 cm with major modes at 90 and 130 cm. Fishes above 80 cm were found to be mature and the size at first maturity was estimated to be between 90-95 cm. Males were dominant with a male: female ratio of 1: 0.58. The length weight relationship is given by the formula W= 0.008634L 3.12. Food contents consisted of a variety of prey animals. Fishes (bony pelagic fishes), crustaceans (crabs and shrimps) and molluscs (squids) were the major prey groups. The fishery is still in its infancy and more research has to be carried out to understand its biology and formulate proper management measures to sustainably harvest this stock.

Associations between seabirds and subsurface predators around Oahu, Hawaii

Many species of tropical seabirds rely on subsurface predators such as tuna and dol- phins to drive prey close to the ocean's surface. We observed seabird foraging events from fishing vessels around the island of Oahu, Hawaii, to determine the prevalence and relative importance of different subsurface predators to seabird foraging. Sixty-nine seabird foraging events were observed, in 62 of which the presence and/or identity of subsurface predators could be determined. Of those 62, all but two involved subsurface predators and accounted for 99.8% of all foraging birds. Skipjack tuna Katsuwonus pelamis were the predominant (81%) subsurface predator involved in seabird feed- ing events, with odontocetes Stenella attenuata and Pseudorca crassidens (8%), mahimahi Coryphaena hippurus (6%), and yellowfin tuna Thunnus albacares (2%) being less common. Wedge- tailed shearwaters Puffinus pacificus and brown noddies Anous stolidus foraged in association with tuna schools more often than would be expected by chance alone. Red-footed boobies Sula sula, in contrast, did not associate with any subsurface predator in greater proportion than what would be expected by chance. Nine additional seabird species were observed foraging in association with sub- surface predators, but not in numbers large enough for statistical analysis. This study highlights the value of regional investigations able to uncover the variable nature of seabird-subsurface-predator associations. The finding that, in Hawaii, at least 2 species of seabirds showed tight dependence on tuna underlines the need for tuna fishery management to address the potential indirect ecological effects of fishing.

Trophic ecology of marine birds and pelagic fishes from Reunion Island as determined by stable isotope analysis

Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine bird and fish communities from Reunion Island, western Indian Ocean. Firstly, isotope signa- tures in the liver of Barau's petrels Pterodroma baraui, Audubon's shearwaters Puffinus lherminieri bailloni, and white-tailed tropicbirds Phaethon lepturus were used to compare their trophic levels and determine whether they forage in the same areas while breeding on Reunion Island. Spatial and trophic segregations were noted among these seabirds. Barau's petrels seem to feed on prey of higher trophic levels than Audubon's shearwaters. Different isotopic signatures in adults and juveniles of these species suggest that these chick-rearing Procellariiformes adopt a dual food-provisioning strat- egy, making separate foraging trips to feed their fledglings and for their own maintenance. Satellite tracking should be undertaken to verify this hypothesis. Furthermore, novel data were obtained on the seabirds' interbreeding period by analyzing feather signatures. White-tailed tropicbirds are thought to change foraging areas during this season, although none of the birds seemed to shift diets. Secondly, isotopic signatures in the muscle of yellowfin tuna Thunnus albacares, skipjack tuna Katsuwonus pelamis, and common dolphinfish Coryphaena hippurus were used to gather informa- tion on their feeding behaviors in Reunion Island waters. Spatial and trophic segregations were also observed, particularly between common dolphinfish and the tuna species, where the former fed more on low trophic level coastal organisms under fish aggregating devices than did the latter. Finally, trophic interactions in bird and fish communities were investigated. Seabirds appear to be trophically more structured than fish, foraging in a wider range of areas. Our results confirmed feeding associa- tions between Audubon's shearwaters and yellowfin tuna.

The Effect of Circle Hooks and Straight (J) Hooks on the Catch Rates and Numbers of White Marlin and Blue Marlin Released Alive by the U.S. Pelagic Longline Fleet in the Gulf of Mexico

AbstractThe effect of circle and straight (J) hooks on the catch rates of white marlin Kajikia albida (formerly Tetrapturus albidus) and blue marlin Makaira nigricans and the proportions released alive by the U.S. pelagic longline fleet targeting yellowfin tuna Thunnus albacares in the Gulf of Mexico was assessed with data collected by scientific observers aboard commercial vessels between 1992 and 2004. Catch rates were lower with circle hooks than with straight hooks, but the differences were not significant; while the catch rates of the targeted species, yellowfin tuna, were the same for both hook types. However, a significantly higher proportion of marlins was released alive from circle hooks than from J hooks.

Turbulence effect on survival and feeding of Pacific bluefin tuna Thunnus orientalis larvae, on the basis of a rearing experiment

Physical conditions such as oceanic turbulence related to food availability are considered to be important factors affecting fish larval survival. Rearing experiments were conducted to elucidate the effects of turbulence on the survival and feeding rates during the initial feeding period of Pacific bluefin tuna Thunnus orientalis. Six levels of turbulence intensity were provided by changing flow rates from pipes set on the bottom of rearing tanks. The result showed a dome-shaped relationship between turbulence level and survival rate, in which the feeding rate appeared higher at a logged turbulence energy dissipation rate of −6.32, and decreased at both higher and lower turbulence levels. Compared with the turbulence intensity in the ocean, the optimal turbulence level for Pacific bluefin tuna larvae corresponded to the turbulence caused by sea surface winds with speeds of 4–12.5 m/s. The estimated optimal turbulence intensity for Pacific bluefin tuna larvae is comparable to that for yellowfin tuna Thunnus albacares.

Drifting fish aggregation devices could act as an ecological trap for tropical tuna species

Purse seine fishing on fish aggregating devices (FADs) has expanded considerably during the last 15 yr in tropical tuna purse seine fisheries, and FADs currently account for about 70 % of their reported tuna catches. The scientific community has expressed concern over the consequences of this fishing practice in terms of yield per recruit and suspected detrimental effects on FAD-associated tunas. To explore possible detrimental effects, we compared stomach fullness, fish plumpness, growth rate, and migration behaviour between free school and drifting FAD-associated tunas for skipjack tuna Katsuwonus pelamis and yellowfin tuna Thunnus albacares caught in the Atlantic and Indian Oceans. Significant differences in fish plumpness and individual growth rates were found, suggesting that individuals associated with drifting FADs were less healthy than those in free schools. Since stomach fullness indicated that tunas associated with FADs eat less than those in free schools, the difference in growth rate and condition could be the consequence of altered feeding patterns. For each species, significant changes in migratory direction and displacement rates were observed in the presence of drifting FADs. These findings support the hypothesis that FADs act as a super-stimulus, misleading tunas to make inappropriate habitat selection. However, further studies are required to investigate the long-term effect of FADs on the entire life cycle of tunas.

35.P5. The effect of heart rate on the monophasic action potential recorded in isolated yellowfin tuna (Thunnus albacares) cardiac muscle

35.P5. The effect of heart rate on the monophasic action potential recorded in isolated yellowfin tuna (Thunnus albacares) cardiac muscle

TLC Analysis of a Corrinoid Compound from Dark Muscle of the Yellowfin Tuna (Thunnus albacares)

A significant amount of vitamin B12 (52.9±8.9 µg/100 g) was found in the dark muscle of the yellowfin tuna (Thunnus albacares), in comparison to that of the light muscle. A corrinoid compound was purified to homogeneity from the dark muscle and partially characterized. TLC and HPLC patterns of the purified corrinoid compound were identical to those of authentic vitamin B12. These results indicate that dark muscle of the yellowfin tuna would be an excellent source of vitamin B12 for humans and aminals.

Effects of retort conditions on ATP-related compounds in pouched fish muscle

To examine the usefulness of high-temperature short time (HTST) process on quality of retorted fish products, adenosine triphosphate (ATP)-related compounds in raw fishes and retorted fish models (10 g/pouch) heated at 115 °C for 90 min (common retort (CR) process) or 125 °C for 9 min (HTST process) were analyzed by HPLC method. The raw materials used in this study were fresh chub mackerel Scomber japonicus for sashimi (raw eating), frozen-thawed yellowfin tuna Thunnus albacares for sashimi, frozen-thawed pink salmon Oncorhynchus gorbuscha for cooking and frozen-thawed pink shrimp Pandalus borealis for sashimi. In all the fish samples, the level of inosine monophosphate (IMP), an umami-taste compound, was higher in HTST fishes than in CR fishes. On the other hand, inosine (HxR) and hypoxanthine (Hx), no-taste and bitter taste compounds, was high in CR fishes. K -value, an index of fish freshness defined as the ratio of the sum of HxR and Hx to the sum of ATP-related compounds, was high in CR fishes. In sensory test of pink salmon by the paired difference test, umami and sweetness in the HTST fish were stronger than the ones of the CR fish. The bitterness was stronger in the CR fish rather than in the HTST fish. These results indicated that HTST is a favorable process for retorted fish product and measurement of ATP-related compounds is useful for the quality check of retorted fishes.

Circle Hooks for Pacific Longliners: Not a Panacea for Marlin and Shark Bycatch, but Part of the Solution

AbstractBlue marlin Makaira nigricans, striped marlin Tetrapturus audax, and pelagic sharks (e.g., blue shark Prionace glauca) are commonly caught as bycatch by longline fisheries in the central North Pacific Ocean. Recently, concern has increased about depletion of these species. Modifications in longline gear may offer one solution. Here, we test the use of circle hooks, rather than the conventional tuna‐style hooks, on longlines using an ecosystem model of the central North Pacific Ocean. The simulations considered span a range of reasonable circle hook catchability and survival rates for released fish. The results suggest that if circle hooks have higher catchability than the currently used tuna‐style hooks, switching to circle hooks depletes marlin biomass by 25–40% and shark biomass by 15–35% over 30 years. However, these depletions do not occur if circle hook catchability is equal to or lower than that of tuna‐style hooks. When the effects of catch‐and‐release requirements for marlins and sharks were also considered, we found that regardless of assumptions about circle hook catchability and survival rates, a combined policy of using circle hooks and releasing sharks and marlins leads to net increases in marlin and shark abundance. The simulations show a trade‐off between the abundance of marlins and sharks and their prey items, yellowfin tuna Thunnus albacares and small blue sharks. There is also evidence of trophic trade‐offs between yellowfin tuna and small blue sharks and their prey, small scombrids (Auxis spp.) and mahi mahi Coryphaena hippurus. The results illustrate the importance of understanding catchability and survival rates for circle hooks compared with those for tuna‐style hooks and encourage further research in this area.

Infection by a Protozoan Endoparasite of the genus Ichthyodinium in Embryos and Yolk-sac Larvae of Yellowfin Tuna Thunnus albacares

In October 2005, a mass mortality of yolk-sac larvae of yellowfin tuna Thunnus albacares due to an endoparasite infection occurred during the seed production in a semi-closed system tank in Bali, Indonesia. Prevalence of the infection reached 100% maximally. The affected embryo or yolk sac of hatched larvae was filled with numerous parasites by 24 h post spawning. The larvae died due to a burst of the yolk sac. Phylogenetic analysis with 18S rRNA sequence and morphological characteristics of the parasite indicated that the present parasite was identified as a protozoan endoparasite Ichthyodinium chabelardi infecting the yolk-sac larvae of Atlantic sardine Sardina pilchardus or as its closely related species. PCR with a primer set designed from the 18S rRNA sequence detected the genome of the parasite from infected fertilized eggs, yolk-sac larvae and rearing water but not from the gonads of broodstock or feed fish for broodstock. The infection was not observed when the spawned eggs were immediately transferred into sterilized seawater, but the eggs kept in the rearing water for more than 1 h were infected by the parasite. These results suggest that the parasite infects fertilized eggs horizontally through the rearing water.

Models of the turning and fast‐start swimming dynamics of aquatic vertebrates

Two models for unpowered and powered turns and C‐type fast‐starts were developed and applied to four different manoeuvres: unpowered turns by a streamlined fish (yellowfin tuna Thunnus albacares), powered turns by an unstreamlined fish (boxfish Ostracion meleagris), fast‐starts (sticklebacks Gasterosteus spp.) and a manoeuvre by a steller sea lion Eumetopias jubatus deploying control surfaces (flippers). The velocity at the end of manoeuvres (terminal velocity) was employed as the ‘benchmark variable’ for comparisons of predicted and actual performance. Good agreement was found in all cases. A log–log plot of available experimental data for turning radius v. mass shows that turning radius scales to the 0·37 power of mass (r2= 0·73), close to the predicted value of 0·33. Recent interests in highly manoeuvrable aquatic vertebrates as biomimetic models for automated underwater vehicles adds to the practical utility of the models presented here.