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The Persimmon Eelpout (Eucryphycus californicus) is a relatively unknown, deep-sea fish inhabiting temperate marine waters on the west coast of North America. Using samples collected in the mid-1970s, the most recent targeted sampling for this species, we present basic life history attributes, and an analysis of the relationship between E. californicus and drift macrophyte habitat in the Monterey Canyon, California, USA. A diet analysis revealed that the fish consumes predominantly small crustaceans, especially amphipods and copepods, including species that associate with drift macrophyte habitat. Otoliths were analyzed to yield age estimates ranging from 0 to 6 years, and growth was modeled showing a maximum length of 203 mm for males and 271 mm for females. An analysis of the reproductive ecology of E. californicus showed that like many deep-sea fishes, females lay relatively few, large eggs. The species exhibits a protracted spawning period, and females spawn with only one functional ovary. Empirical information presented in this paper and anecdotal evidence shows that E. californicus likely relies on drift algae and seagrasses, a habitat subsidy exported to the deep-sea environment from adjacent kelp forest ecosystems, for shelter and to concentrate food resources. This example of a species dependent on an ecosystem subsidy adds to our knowledge regarding the effects of cross-ecosystem connectivity in the marine environment, and furthers our understanding of the ecology of the deep-sea macrofaunal assemblage in Monterey Bay.

Age and growth estimates based on growth band counts of sectioned vertebrae have been produced for longnose skate ( Raja rhina ) and big skate ( Beringraja binoculata [formerly Raja binoculata ]) populations in the Gulf of Alaska, British Columbia and California. Previous growth studies involving estimates from different laboratories in the USA (Alaska Fisheries Science Center, AFSC; Pacific Shark Research Center, PSRC at Moss Landing Marine Laboratories) and Canada (Fisheries and Oceans Canada, DFO) have produced dissimilar results for either species, highlighting the need for development of a consistent age determination protocol and more importantly an age validation study. Archived large specimens of longnose skate and big skate collected in Monterey Bay, CA, in 1980 and 1981 had minimum preliminary age estimates from vertebral growth band counts old enough to suggest that radiocarbon ( 14 C) signals from bomb testing conducted in the late-1960s could be used to establish dates of growth band formation. To this end, we micro-milled skate vertebral thin sections, measured Δ 14 C using mass spectrometry, and estimated year of growth band formation based on the estimated age from growth band counts using both unstained and stained preparation methods Non-linear random effects modeling, implemented in a Markov Chain Monte Carlo (MCMC) simulation, was used to compare the skate Δ 14 C data set to a marine teleost otolith reference chronology for the California Current System. Results showed Δ 14 C measurements for big skate were non-informative as none of the archived samples were old enough for comparison to the reference curve, hence validation of the age estimation approach was not possible. However, for longnose skate, Δ 14 C data were more informative to fit pulse function models and compare results to the reference chronology. Modeling results indicated longnose skate age estimates based on unstained vertebral thin sections were less biased (overestimated to a smaller degree) than estimates based on stained vertebral thin sections. The degree of bias depended on agency ageing criteria, with the least biased age estimates produced by age readers from the AFSC. The AFSC age estimates had about a 70% probability that age estimates of longnose skate was within +/− 2 years of the expected age based on the radiocarbon assays. We were able to validate the age estimation methodology for longnose skate and establish criteria for growth band counts, which should now be useful to generate region-specific accurate growth and life history parameters required for more reliable stock assessment approaches.

Garden eels occur worldwide in the tropics, but little is known about their biology and ecology. We studied Hawaiian garden eel ( Gorgasia hawaiiensis ) colonies near Kawaihae, Hawai‘i, to investigate multiple aspects of basic biology of this species. Colonies of G. hawaiiensis occurred at depths from 16 to 36 m in soft-bottom habitat adjacent to rocky reefs. Highest burrow densities (up to 40 eels m−2) were in shallower water, and large (~10 mm diameter) burrows were more abundant, less dense, and commonly found in pairs in deeper water. Eels emerged around sunrise and withdrew and covered burrow entrances around sunset. Age was estimated from annual rings in sectioned otoliths ( n = 17) and modeled to suggest fast growth to a maximum size of ~600 mm total length and a maximum age of 6 yr. Prey size and eel anatomy suggest that these fish feed by ingesting planktonic prey and processing them in the esophagus. The most common food items were small ( G. hawaiiensis is abundant, has a high population turnover rate, and may enrich sandy-bottom habitat within their beds by facilitating energy flow from the water column to the benthos.

Made available in DSpace on 2020-12-10T20:13:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-11-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The age and growth of three endemic threatened guitarfish species were analysed using vertebrae of Pseudobatos horkelii, P. percellens and Zapteryx brevirostris. Edge and marginal-increment analyses were used to evaluate the periodicity of the formation of the band-pairs, suggesting deposition of one band-pair per year, from late winter to late spring. The von Bertalanffy growth model was used to describe the growth of these species with the following parameters, for pooled sexes: P. horkelii L-infinity = 126.93, k = 0.19 and t(0) = -1.51; P. percellens L-infinity = 109.31, k = 0.16 and t(0) = -1.78; Z. brevirostris L-infinity = 60.37, k = 0.24 and t(0) = -1.42. Our results are essential to understanding the resilience and vulnerability of these species to harvest, which can contribute to management and conservation actions of these species. Sao Paulo State Univ, Dept Biol Sci, Botucatu, SP, Brazil Univ Florida, Sch Forest Resources & Conservat, Fisheries & Aquat Sci Program, 427 McCarty Hall C,POB 110410, Gainesville, FL 32611 USA Univ Fed Sao Paulo, Marine Ecol & Conservat Lab LABECMar, Santos, Brazil Moss Landing Marine Labs, Pacific Shark Res Ctr, Pob 450, Moss Landing, CA 95039 USA Sao Paulo State Univ, Biosci Inst, Elasmobranch Lab, Sao Paulo, Brazil Sao Paulo State Univ, Dept Biol Sci, Botucatu, SP, Brazil Sao Paulo State Univ, Biosci Inst, Elasmobranch Lab, Sao Paulo, Brazil FAPESP: #2010/02397-7 FAPESP: #2012/00713-4

The eighth in a series of workshops on fish feeding ecology (“Gutshops”) was held in 2015, continuing a tradition started in 1976 that expanded in scope and participation. Topics in early Gutshops focused on methodology and analysis, and evolved to include niche overlap, competition, nutrition, and community trophic interactions. Major accomplishments were enhanced communications, standardization, design and evolution of indices (IRI, GII, PSIRI, etc.), statistical improvements, graphics, and chemical studies such as stable isotope and fatty acid analyses. Future directions, some of which were presented at the 2015 meeting, include internal tags (detecting feeding through movements, acidity, temperature, etc.), additional stable isotope and fatty acid analyses, genetic identification of prey and physiological indicators (enzyme analysis and digestion processes).

The Aleutian skate (Bathyraja aleutica) is a large deep-water species that commonly occurs in bycatch of Alaskan trawl and longline fisheries. Although prominent in the skate biomass of the eastern Bering Sea (EBS) and Gulf of Alaska (GOA) ecosystems, minimal biological information exists. To increase our understanding of this potentially vulnerable species, and address the possibility of two separate populations in Alaskan waters, the age and growth of B. aleutica was studied. Vertebral centra were examined for age determination, and multiple growth models were evaluated to determine growth characteristics. Skates from the EBS attained maximum ages of 17 and 16 years for females and males, respectively, and the two-parameter von Bertalanffy growth functions generated estimates of k = 0.13 yr.-1 and L∞ = 162.1 cm for females, with similar results for males. Skates from the GOA reached 19 years in females and 18 years in males. Growth parameters of female skates from the GOA were estimated as k = 0.11 yr.-1 and L∞ = 160.0 cm, whereas males grew faster, with estimates of k = 0.15 yr.-1 and L∞ = 138.2 cm. The results of this study may indicate the presence of distinct populations of B. aleutica in the eastern North Pacific.

Made available in DSpace on 2020-12-10T20:09:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-08-20 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Owing to poorly mineralising structures, ageing deep-water elasmobranchs requires unconventional techniques. The aim of the present study was to develop an ageing method for the goblin sharkMitsukurina owstoni(Jordan, 1898) using Alcian blue staining of the vertebral column. One vertebral centrum from a male individual measuring 315.2-cm total length (TL) was aged with a minimum age of 27 years. Using a Bayesian von Bertalanffy growth model informed by back-calculated length at age, a literature search of maximum male TL, the TL of the smallest free-swimming individuals and informative priors, we estimated males grow to 374 cm TL, mature at 16 years and live up to 60 years. Our results provide useful life history information, with the aim of elucidating the cryptic biology of this deep-water shark. Oregon State Univ, Coastal Oregon Marine Expt Stn, 2030 SE Marine Sci Dr, Newport, OR 97365 USA Univ Florida, Sch Forest Resources & Conservat, Fisheries & Aquat Sci Program, 118 Newins Ziegler Hall,POB 110410, Gainesville, FL 32611 USA Moss Landing Marine Labs, Pacific Shark Res Ctr, 8272 Moss Landing Rd, Moss Landing, CA 95039 USA Univ Fed Sao Paulo, Marine Ecol & Conservat Lab, Rua Dr Carvalho de Mendonca 144, BR-11070100 Santos, SP, Brazil Sao Paulo State Univ, Biosci Inst, Elasmobranch Lab, Praca Infante Dom Henrique S-N,Parque Bitaru, BR-11380972 Sao Vicente, SP, Brazil Sao Paulo State Univ, Biosci Inst, Elasmobranch Lab, Praca Infante Dom Henrique S-N,Parque Bitaru, BR-11380972 Sao Vicente, SP, Brazil FAPESP: 2010/02397-7

Life-history (age, growth, age validation, reproduction and demography) studies of elasmobranchs date back to the middle of the last century with major early contributions made by British fishery scientists. As predicted by Holden in the early 1970s, many sharks and rays can be vulnerable to fishery mortality because they grow slowly, mature late in life, reproduce infrequently, have relatively low fecundities and can have relatively long life spans. As has now been found, however, not all species exhibit these traits. Also, ageing structures (neural arches and caudal thorns), other than vertebrae and spines, have since been evaluated. Various methods for validating age and growth estimates have been developed and tested on numerous species of elasmobranchs. These include tag-recapture analyses, oxytetracycline injections, centrum or spine edge and marginal increment analyses, and bomb radiocarbon dating of calcified structures. Application of these techniques has sometimes not only validated relatively slow growth and long life span estimates, but also has produced other results. A brief historical perspective on the applications and limitations of these techniques for elasmobranchs is provided, along with a discussion of selected species for which these techniques worked well, did not work at all or have produced variable and conflicting results. Because many fishery management techniques utilize age or stage-specific information, often through demographic analyses, accurate information on the life histories of fished populations, especially age validation, is extremely important for the fishery management of these cartilaginous fishes.

The Bering skate, Bathyraja interrupta , is commonly found in both the Bering Sea and Gulf of Alaska, where skates are a regular bycatch in commercial long line and bottom trawl fisheries. This is the first study to examine the age and growth of B. interrupta , and one of the few studies to directly compare growth parameters of a skate species between management regions. Ages were estimated based on band counts using the standard gross-sectioning method of vertebral centra preparation. Additionally, a preliminary investigation was conducted into the utility of the histological method. Several growth models were compared and the best-fit model for both regions was identified as the logistic model using the Akaike's Information Criterion approach. No significant difference was detected between sexes for any model in either region; however, a slight but significant difference was found between regions. The parameters of the logistic growth model based on the gross-sectioned preparation were L ∞ = 82.80 cm TL and k −1 yr = 0.23 for the eastern Bering Sea and L ∞ = 86.94 cm TL and k −1 yr = 0.20 for the Gulf of Alaska. Age estimates from the gross sectioned vertebral centra provided a minimum longevity of 19 years and 21 years, respectively. Estimates based on the histologically prepared samples provide overall slightly higher age estimates, but the same maximum age of 21 years.

Vertebrae of most deep-water sharks are too poorly calcified to record visible growth bands and therefore are not useful for age determination. Most dogfish species (Order: Squaliformes) possess dorsal finspines and several recent studies have shown that these structures offer potential for age determination. Age validation should be central to any age determination study, yet to date no age and growth study of deep-water sharks has included a complete validation of age estimates. In this study we sought to age two deep-water dogfish species by analyzing 210Pb and 226Ra incorporated into the internal dentin of the finspines. These radiometric age estimates were compared with counts of internal growth bands observed in the finspines. A pilot study indicated that dorsal finspines of Centroselachus crepidater are too small and thus offer insufficient mass for the radiometric techniques employed in this study. For ageing larger finspines of Centrophorus squamosus, the lead–radium disequilibria method (ingrowth of 210Pb from 226Ra) was found to be inapplicable due to exogenous uptake of 210Pb in the finspine. Therefore, to approximate age, we measured the decay of 210Pb within the dentin material at the tip of the finspine (formed in utero), relative to the terminal material at the base of the finspine. Results with this method proved to be inconsistent and did not yield reliable age estimates. Hence the use of 210Pb and 226Ra for radiometric age determination and validation using dorsal finspines from these deep-water dogfishes was deemed unsuccessful. This outcome was likely due to violations of the consistent, life-long isotopic uptake assumption as well as the provision that the finspine must function as a closed system for these radioisotopes. Future improvements in analytical precision will allow for smaller samples to be analyzed, potentially yielding a better understanding of the fate of these radioisotopes within finspine dentin throughout the life of the shark.

The sandpaper skate, Bathyraja kincaidii, is commonly taken as bycatch in trawl fisheries off central California. The impact of fisheries exploitation on this population is unknown, however little is known about its biology, including its reproductive life history. To determine reproductive aspects of B. kincaidii, 506 individuals were collected from commercial trawls, museum collections, and monthly trawl and longline surveys conducted by the National Marine Fisheries Service. Males ranged from 112 to 635 mm TL, whereas females ranged from 113 to 610 mm TL. Males reach first maturity at 440 mm TL and at ~3 years, whereas females reach first maturity at 450 mm TL, approximately 1 year later. Size and estimated age at 50 % maturity were similar between sexes: 492 mm TL and 7.5 years for males and 467 mm TL and 7.1 years for females. Gonadosomatic index (GSI) and hepatosomatic index (HSI) values indicate a continuous reproductive cycle, with a seasonal peak in the summer and fall, and a resting period following egg case deposition.

Although many skates possess life history characteristics that may make them vulnerable to exploitation, the detailed biological information needed to enact effective management schemes is lacking for most species. The objectives of this study were to provide age, growth, and maturity estimates for the roughtail skate, Bathyraja trachura, from the eastern Bering Sea. Maximum age was estimated at 36 yr based on band pair counts in vertebral centra. Of the four growth models applied, the logistic model provided the best description of growth (asymptotic total length = 911 mm; growth coefficient = 0.131 yr−1). There was no evidence of difference in growth between males and females. Females attained maturity at larger sizes and older ages than males. The median size-at-maturity was estimated at 741 mm total length (TL) for males and 796 mm TL for females; median age-at-maturity was estimated at 21.1 yr and 24.7 yr for males and females, respectively. The results of this study may indicate a latitudinal pattern in size and growth, with individuals from the eastern Bering Sea growing more slowly and reaching higher maximum ages than previously reported for specimens collected off the western coast of the continental United States.

Skates are prevalent in fisheries worldwide, but rarely are they identified to species. This is of conservation and management concern since skates exhibit a broad range of life history characteristics. The present study investigated the age and growth of the Starry Skate, Raja stellulata, and compared it to other regional skates inhabiting the U.S. West Coast. Age and growth parameters were determined using two vertebral preparation techniques: gross sectioning and histological sectioning. Gross section age estimates ranged from zero to 11 years and growth was described by the two parameter von Bertalanffy growth function (2 VBGF; L ∞ = 915 mm total length (TL) and k = 0.13 year-1; n = 189). Histological section age estimates ranged from zero to 15 years and growth was also described by the 2 VBGF (L ∞ = 1092 mm TL, k = 0.06 year-1; n = 68). Histological section results reflect a more conservative life history, specifically a lower von Bertalanffy growth coefficient, but had slightly biased results and a smaller sample size than the gross section results. An age and depth trend was found within the central California skate assemblage, in which habitat depth and maximum age were positively correlated.

The ability of six grenadier species from the North Atlantic, North Pacific, and Southern Ocean to sustain deep-sea fisheries is assessed. These species are captured in high amounts as bycatch and a few are taken in targeted fisheries, yet population status for most is poorly known or known for only a small portion of their range. A productivity and susceptibility analysis showed that none of the species was highly productive, which was not unexpected given their life history characteristics. While grenadiers were ranked more vulnerable than species in the northeastern Pacific groundfish fisheries, none of the investigated species was ranked as highly susceptible or heavily exploited. This result exposed several weaknesses in the PSA technique and attribute scoring. Management actions and regulations are discussed, which, if employed, might make grenadier fisheries sustainable., Sí

In situ observations and collections of Chaunacops coloratus ( Garman, 1899 ) from seamounts in the eastern North Pacific Ocean lend new behavioral, morphological and molecular data to an under-sampled, deep-sea group of fishes in the order Lophiiformes. Seven observations were made at Davidson Seamount, 130 km southwest of Monterey, CA, and from the Taney Seamount chain, 290 km west of Moss Landing, CA, from depths ranging from 2313 to 3297 m. Specimens were collected at both locations. Morphometric and meristic analyses were performed to identify individuals to the species level. These observations of C. coloratus provide greater latitude and depth distributions in the eastern North Pacific Ocean than previously known. Detailed habitat information indicated the fish occurred near manganese-encrusted volcanic talus slopes, a highly rugose habitat. Video observations revealed possible ontogenetic color changes in which small fish were blue and large fish were red. Video recorded rapid, vertical swimming as an escape response and maneuvering, or walking, with pectoral and pelvic fins and esca deployment. Phylogenetic analyses used here verify what has been known since Garman first described C. coloratus in 1899, that Chaunax and Chaunacops are closely related; molecular tools complement previous knowledge and genetic information created has been submitted to GenBank for further use by the scientific community.

Results presented here provide evidence of an exception to the generalization that all chondrichthyan populations are especially vulnerable to exploitation to the extent that they remain at low abundance for a protracted or indefinite duration even after exploitation rates are reduced. Delta log-normal generalized linear models (GLM) and cluster analysis of fishery-independent catch-per-unit-effort (CPUE) data from 1977 to 2006 indicated the presence of at least two distinct stocks of spotted ratfish Hydrolagus colliei off the U.S. West Coast. CPUE of the continental slope and northern continental shelf and upper slope populations did not vary between 1977 and 1995 and increased from 1995 to 2006. On the basis of the timing of these changes, it is likely that both fishing and climate influenced these trends. Sex and size-specific differences in bathymetric distribution, along with the identification of nursery sites, indicate that fishery by-catch could have a significant effect on population growth. These aggregative behaviours, combined with low fecundity, indicate that H. colliei may be vulnerable to irreversible population depletion by fisheries mortality. Temporal abundance trends indicated, however, that their population size has increased significantly within the last decade, a demonstration of population stability. A literature review indicated that there is also evidence for population stability in other chondrichthyans. The paradigm that all chondrichthyan populations fail to rebuild in response to exploitation, therefore, may not be as broadly applicable as previously thought. Thus, it is not necessarily sufficient to make generalizations regarding the vulnerability of chondrichthyans across higher taxonomic scales.

Characterization of fish diets from stomach content analysis commonly involves the calculation of multiple relative measures of prey quantity (%N,%W,%FO), and their combination in the standardized Index of Relative Importance (%IRI). Examining the underlying structure of dietary data matrices reveals interdependencies among diet measures, and obviates the advantageous use of underused prey-specific measures to diet characterization. With these interdependencies clearly realized as formal mathematical expressions, we proceed to isolate algebraically, the inherent bias in %IRI, and provide a correction for it by substituting traditional measures with prey-specific measures. The resultant new index, the Prey-Specific Index of Relative Importance (%PSIRI), is introduced and recommended to replace %IRI for its demonstrated more balanced treatment of the relative measures of prey quantity, and less erroneous behavior across taxonomic levels of identified prey. As a case study, %PSIRI was used to examine the diet of the Aleutian skate Bathyraja aleutica from specimens collected from three ecoregions of the northern Gulf of Alaska (GOA) continental shelf during June-September 2005–2007. Aleutian skate were found to primarily consume the commonly abundant benthic crustaceans, northern pink shrimp Pandalus eous and Tanner crab Chionoecetes bairdi, and secondarily consume various teleost fishes. Multivariate variance partitioning by Redundancy Analysis revealed spatially driven differences in the diet to be as influential as skate size, sex, and depth of capture. Euphausiids and other mid-water prey in the diet were strongly associated with the Shelikof Strait region during 2007 that may be explained by atypical marine climate conditions during that year.

Information on the distribution of three species of eastern North Pacific (ENP) catsharks (Apristurus brunneus, Apristurus kampae, and Parmaturus xaniurus) and their egg cases was previously unavailable despite being a species of interest for fisheries management evaluation and policy regulation. Data were generated from specimens collected by survey cruises from June 2001 through October 2004 between northern Washington to San Diego, California, U.S.A. and from known catch locations of specimens in museum collections. Longline catches consisted mainly of P. xaniurus, with occasional catch of gravid female A. brunneus. Conversely, trawl catches consisted mainly of Apristurus species. The three catshark species exhibited distinct differences in latitudinal and bathymetric range, albeit with partial overlap. Apristurus brunneus was typically found between 300 and 942 m along the entire area surveyed, while A. kampae always occurred .1,000-m depth and was not found north of 426N. Parmaturus xaniurus was caught between 300- and 550-m depth between 406N and 326N. Egg cases of A. brunneus and P. xaniurus were collected in trawl surveys and observed in video footage taken by remotely operated vehicle. These egg cases were located in specific sites on areas of high vertical relief at 300- to 500-m depth. Nursery grounds, which were previously unknown for these catshark species, were described within the Monterey Bay Canyon and along the California coastline were identified on the basis of recurrence and specificity of oviposition. This paper describes the range of A. brunneus, A. kampae, and P. xaniurus in the ENP, detailing latitudinal, bathymetric, sexual, and ontogenetic intra- and interspecific segregation patterns.

A new species of sawshark, Pristiophorus nancyae sp. nov., is described from eight specimens collected off mozambique. The new species is the second member of the family pristiophoridae and first member of the genus Pristiophorus described from the western indian ocean. The new Pristiophorus species can be distinguished from the sympatric occurring six-gilled sawshark, Pliotrema warreni regan, 1906, most notably by having five paired gill openings as opposed to six. The new species is distinguished from all other Pristiophorus species by several distinctive characteristics. most notably, the new species differs by having a very distinctive double row of four to five conspicuous large pits anterior to the nasal barbels on the underside of its snout. other distinguishing characteristics include a broad, triangular first dorsal fin with a rear tip that extends behind the pelvic midbases, barbels much closer to mouth than snout tip, two rows of enlarged pits on the underside of the pre-barbel rostrum, ridges on the base of its large lateral rostral teeth, mostly tricuspidate, flat, imbricated lateral trunk denticles, and plain color pattern. The new species is compared to the five other known Pristiophorus species and a revised key to the genus is presented.

Ainsley, S. M., Ebert, D. A., and Cailliet, G. M. 2011. Age, growth, and maturity of the whitebrow skate, Bathyraja minispinosa, from the eastern Bering Sea. – ICES Journal of Marine Science, 68: 1426–1434. Skates are a common bycatch in groundfish fisheries in the Bering Sea; however, their life-history characteristics are not well known. The study is the first to investigate the age, growth, and age at maturity of Bathyraja minispinosa. Ages were estimated using sectioned vertebrae and several growth models were compared. The Gompertz model was the best fit and no significant differences were detected between sexes for any model. The maximum age estimated was 37 years, and parameter estimates generated from the three-parameter von Bertalanffy model were k = 0.02 year−1 and L∞ = 146.9 cm total length (TL). Males reached their size at 50% maturity larger than females (70.1 and 67.4 cm, respectively), but no significant differences in the estimated size or age at maturity were found. Whereas B. minispinosa is smaller than many skate species in the eastern Bering Sea, it has a considerably longer estimated lifespan, indicating that size may not be a reliable method of estimating the vulnerability of a rajid species to population declines in the eastern North Pacific.

The sandpaper skate,Bathyraja kincaidii, is one of four skate species commonly taken in trawl fisheries off central California although very little is known about its life history. In this study, age and growth were evaluated from 187 vertebrae using a common growth band counting method. An attempt to use marginal increment analysis and centrum edge analysis failed to validate the annual periodicity of growth band formation; however, it is a valid assumption based on structural similarity from other studies. Assuming annual band formation, von Bertalanffy growth parameters were determined for females (L∞ = 537.3 mm; k = 0.237; to = –1.629; N = 99) and males (L∞ = 580.2 mm; k = 0.185; to = –2.530; N = 88). Maximum likelihood ratios indicated no significant difference (P > 0.05) between male and female von Bertalanffy growth parameters, thus data were combined (L∞ = 557.8 mm; k = 0.207; to = –2.147; N = 187). Age estimates from band counts in vertebral centra indicated a minimum longevity of 17 and 18 years for female and maleB. kincaidii, respectively. Caudal thorns were also assessed for age analyses, but were deemed unreliable and could not be used to verify age estimates from vertebral centra.

Antarctic toothfish (Dissostichus mawsoni) are the target of an important commercial fishery in the Southern Ocean, yet age data used for management have not been comprehensively tested for accuracy. In this study, Antarctic toothfish were aged using counts of otolith growth zones based on criteria established for Patagonian toothfish, D. eleginoides, a closely related species. To validate these ages, the radioactive disequilibrium of lead-210 and radium-226 in otolith cores was measured and used as an independent chronometer to accurately determine age across the range of fish caught in large numbers by the fishery. Growth-zone counts indicated Antarctic toothfish live to at least 39 years of age, and were in close agreement with the chronometer, validating the age estimation criteria and the accuracy of age estimates. Von Bertalanffy growth function parameters indicated Antarctic toothfish were relatively slow-growing (k = 0.111), especially in relation to their maximum size (L ∞ = 158.9 cm).

Previous attempts to age chimaeroids have not rigorously tested assumptions of dorsal fin spine growth dynamics. Here, novel imaging and data-analysis techniques revealed that the dorsal fin spine of the spotted ratfish Hydrolagus colliei is an unreliable structure for age estimation. Variation among individuals in the relationship between spine width and distance from the spine tip indicated that the technique of transverse sectioning may impart imprecision and bias to age estimates. The number of growth-band pairs observed by light microscopy in the inner dentine layer was not a good predictor of body size. Mineral density gradients, indicative of growth zones, were absent in the dorsal fin spine of H. colliei, decreasing the likelihood that the bands observed by light microscopy represent a record of growth with consistent periodicity. These results indicate that the hypothesis of aseasonal growth remains plausible and it should not be assumed that chimaeroid age is quantifiable by standard techniques.

In many regions of the world, commercial fisheries for seamount-aggregating species have collapsed. Most are trawl fisheries, which have been implicated in the destruction and loss of fragile coral and sponge habitat and potentially endemic seamount species. Even with the intense fishing effort over seamounts, our understanding of processes regulating the distribution and abun- dance of seamount fish assemblages, which is vital to conservation policy, is weak. Here, we describe the abundance and distribution of demersal fishes found on 3 seamounts off central and southern California. Video observations were taken during 27 dives of a remotely operated vehicle (ROV), and were annotated in detail using the Monterey Bay Aquarium Research Institute's (MBARI) Video Annotation Reference System (VARS). Video analysis yielded 2151 observations of 36 identified taxa. No aggregations of fishes were observed during the surveys. Video transects were analyzed to quan- tify organism density. Similarity among seamounts was compared using Bray-Curtis similarity esti- mates. Our results indicate high similarity among seamount faunas at similar depths, a shift from provincial to abyssal/cosmopolitan species with increased depth, and no evidence of seamount endemism.

The Mexican elasmobranch fishery ranks among the most important in the world, but details associated with fishing effort and species composition are generally unavailable, particularly for the extensive artisanal fishery. Seasonal surveys were conducted during 1998–1999 in the state of Baja California to determine the extent and activities of the artisanal elasmobranch fishery along its Gulf of California coast. Artisanal fishermen were highly opportunistic, and temporally switched targets depending on the local abundance of teleost, invertebrate, and elasmobranch fisheries resources. At least 17 species of shark, 13 species of ray, and 2 species of skate were identified among the 4495 specimens observed. Small, coastal sharks and rays were typically landed with bottom set gillnets during all surveyed seasons (spring–autumn) and large sharks were targeted with surface set (drift) gillnets during summer and autumn. Sharks and rays contributed similarly to elasmobranch landings, comprising 50.9% and 48.3%, respectively, of the total recorded catch. Overall landings were dominated by mustelid sharks (Mustelus henlei, Mustelus spp.) and the shovelnose guitarfish (Rhinobatos productus), with Alopias pelagicus, Gymnura spp., Heterodontus mexicanus, Mobula munkiana, Myliobatis californica, and Squatina californica also representing important components of the landings. Alopias vulpinus had previously been unreported for the Gulf of California and a new maximum size record was documented for Myliobatis longirostris. Catch rates (mean elasmobranchs/vessel/trip ± standard error) were lowest during autumn (17.4 ± 3.9) and highest in spring (35.3 ± 14.1). Adult, commonly gravid, A. pelagicus, Carcharhinus falciformis, and R. productus females comprised a disproportionately greater component of the landings than did their male counterparts. Given the decades of largely unrestricted exploitation of elasmobranchs in Mexican waters, population declines and shifts in size structure are likely to have occurred among those species with the lowest fecundity and latest ages at maturity.

Size at maturity, fecundity, and reproductive periodicity were estimated for the spotted ratfish, Hydrolagus colliei (Lay and Bennett, 1839), off the coast of California, Oregon, and Washington. Maximum body size and size at median maturity were greater for females than males. Skeletal muscle concentrations of the steroid hormones testosterone (T) and estradiol (E2) predicted similar, but slightly smaller sizes at maturity than the morphological criterion. Stage of maturity for males was estimated identically using internal organs or external secondary sexual characters, thus allowing non-lethal maturity assessments. Size at median maturity was greater north of Point Conception for females, and north of Cape Mendocino for males. Peak parturition occurred from May to October, with increased concentrations of E2 in skeletal muscle of females correlating with ovarian recrudescence during November to February. No significant seasonal trends in female T were apparent, but mean female 11-ketotestosterone (11KT) was 300% greater in April than any other month during the parturition season. There was a marginal evidence for increased number and size of ova with maternal size. Extrapolation of the hypothesized 6 to 8-month egg-laying season to observed mean parturition rates of captive specimens yielded an estimated annual fecundity of 19.5–28.9 egg cases. Differences in fecundity among higher taxonomic classifications of chondrichthyans were detected with chimaeriform fishes more fecund than lamniform, myliobatiform, squaliform, and rhinobatiform fishes, and less fecund than rajiform fishes.

Seamounts are unique and biologically productive deep-sea habitats that have often been described as having high levels of endemism, highly productive fisheries, and benthic commu- nities vulnerable to trawl fishing. We describe the abundance and distribution of benthic megafaunal invertebrates found on 3 seamounts off central and southern California. Video observations were taken during 27 dives of a remotely operated vehicle (ROV) and were annotated in detail using the Monterey Bay Aquarium Research Institute's (MBARI) video annotation reference system (VARS, http://vars.sourceforge.net/). Video analysis yielded 134 477 observations of 202 identified inverte- brate taxa. Video transects were analyzed to quantify organism density. Thirteen new species were observed and collected. Invertebrate communities at Davidson and Pioneer Seamounts were domi- nated by passive suspension-feeding cnidarians (mostly corals), but at Rodriguez Seamount, a guyot, the invertebrate community was dominated by holothurian echinoderms. We found no evidence of endemism among the megafauna at these 3 seamounts, which are all in close proximity to each other and the continental margin.

Analysis of bomb generated radiocarbon ( 14 C) changes in a red abalone, Haliotis rufescens Swainson shell was used to evaluate age-at-length relationships derived from data from a previous multiyear, multisite tag-recapture study. Shell carbonate was extracted from four successive growth trajectory locations in a single shell with a maximum shell length of 251 mm. Extraction locations were based on Von Bertalanffy growth function (VBGF) predictions and chosen to span the initial rise of the 14 C-bomb pulse that is known to have occurred in surface ocean waters during 1958 ±1 y in the northeast Pacific. The close temporal correspondence of the red abalone sample series to regional D 14 C records demonstrated the utility of the technique for validating age-at-length relationships for the red abalone. The findings provided support for a mean VBGF derived age of 32 y (range 30-33 y) for the specimen; however, the analysis of 14 C data indicated that the specimen could be older.

This study provides the first detailed information on the reproductive biology of two large and abundant eastern North Pacific Ocean skate species: big skate (Raja binoculata) and longnose skate (Raja rhina). Skates were collected in the western Gulf of Alaska during 2005 and 2006 after a targeted fishery for these two species developed around Kodiak Island, Alaska; both species are also taken as by-catch to other fisheries. A total of 307 females (20.1–183.3 cm TL) and 138 males (19.5–143.7 cm TL) R. binoculata, and 354 females (18.1–145.0 cm TL) and 318 males (21.1–135.8 cm TL) R. rhina were collected. Female R. binoculata were found to attain first (e.g., smallest individual) maturity at 125.8 cm TL and 50% at 148.6 cm TL. Males were found to attain first and 50% maturity at 124.0 and 119.2 cm TL, respectively. No gravid female R. binoculata, with egg cases in utero, were encountered during the study. Female R. rhina were found to attain first and 50% maturity at 102.2 and 113.1 cm TL, respectively. Gravid female R. rhina, with egg cases in utero, were recorded throughout the sampling period. Males attained first maturity at 101.0 cm TL and 50% maturity at 102.9 cm TL. Histological analysis did not reveal significant changes in spermatocyst production for either species during the sampling period. Both species appear to be reproductively active year-round as no seasonal cycle was evident. This study provides new and essential information on the reproductive biology of these two commercially targeted skate species. © 2008 Elsevier B.V. All rights reserved.

This study provides the first published age estimates for the roughtail skate, Bathyraja trachura. Age and growth characteristics of B. trachura, a poorly-known deepwater species, were determined from samples collected along the continental slope of the contiguous western United States. A new maximum size was established at 91.0 cm TL. Age was determined using a traditional structure (vertebral thin sections) with widespread application on multiple skate species and a non-lethal structure (caudal thorns) recently used for age analysis on skate species. Caudal thorns were determined not to be a useful ageing structure for this species based on poor precision and significantly lower age estimates when compared to age estimates from vertebral thin sections. The best model for describing growth of B. trachura was the two parameter VBGF, assuming annual vertebral band deposition and using length-at-age data. Although females grew slower and reached a larger maximum size than males, their growth was not statistically different (ARSS; P = 0.90); therefore, data were pooled (L∞ = 99.38, k = 0.09). Annual band deposition was found to be a reasonable assumption for this species, but has yet to be validated. The maximum age estimated for B. trachura was 20 years for males and 17 years for females using vertebral thin sections.

Feeding studies can provide researchers with important insights towards understanding potential fishery impacts on marine systems. Raja rhina is one of the most common elasmobranch species landed in central and northern California demersal fisheries, yet life history information is extremely limited for this species and aspects of its diet are unknown. Specimens of R. rhina were collected between September, 2002 and August, 2003 from fisheries-independent trawl surveys. Percent Index of Relative Importance values indicated that the five most important prey items in 618 stomachs of R. rhina were unidentified teleosts (31.6% IRI), unidentified shrimps (19.6% IRI), unidentified euphausiids (10.9% IRI), Crangonidae (7.4% IRI), and Neocrangon resima (6.0% IRI). There were significant dietary shifts with increasing skate total length and with increasing depths. Smaller skates ate small crustaceans and larger skates ate larger fishes and cephalopods. With increasing depths, diet included bentho-pelagic teleosts and more cephalopods and euphausiids. The findings of this study are consistent with previous researchers that report similar diet shifts in skate species with size and depth.

The stomachs of 130 sandpaper skates, Bathyraja kincaidii (Garman, 1908), were sampled from off central California to determine their diet composition. The overall diet was dominated by euphausiids, but shrimps, polychaetes and squids were also important secondary prey. A three-factor MANOVA demonstrated significant differences in the diet by sex, maturity status and oceanographic season using numeric and gravimetric measures of importance for the major prey categories. These three main factors explained more variation in diet than interactions between the factors, and season explained the most variance overall. A detailed analysis of the seasonal variation among the prey categories indicated that abundance changes in the most important prey, euphausiids, were coupled with seasonal changes in the importance of other prey. When upwelling occurred and productivity was great (Upwelling and Oceanic seasons), euphausiids were likely highly abundant in the study area and were the most important prey for B. kincaidii. As productivity declined (Davidson Current season), euphausiids appeared to decrease in abundance and B. kincaidii switched to secondary prey. At that time, gammarid amphipods and shrimps became the most important prey items and polychaetes, mysids and euphausiids were secondary.

Apristurus brunneus, A. kampae, and Parmaturus xaniurus were caught by trawl and longline between Washington and southern California (48°N to 32°N latitude) from June 2001 through October 2004. In females, oviducal gland width increased with TL in all three species but remained within 4 to 6% of TL. Oocyte diameter increased with TL during reproductive development in all species, and continued to increase with size after reproductive maturity was reached. The weight-length relationships differed significantly among species but not between sexes of any species from the eastern North Pacific combined. Using logistic regression, it was determined that total length at 50% maturity (TL50) of A. brunneus males was 514 mm TL and all A. brunneus males were mature at 547 mm TL. Female A. brunneus reached TL50 at 501 mm TL and all female A. brunneus were mature at 581 mm TL. Apristurus kampae males and females reached TL50 at approximately 485 mm TL and 490 mm TL, respectively. Parmaturus xaniurus males reached TL50 at 444 mm TL and females at 501 mm TL. Gravid female A. brunneus were found in all months of the year, but gravid P. xaniurus were found primarily June through September. Adult A. kampae females were found only in July through November and there were gravid females in all these months. Based upon gonadosomatic indices, IG, these species may mate within a defined period of time (April through June); however, A. brunneus appear to reproduce throughout the year and P. xaniurus reproduce within a defined season (approximately July through September).

The bank rockfish, Sebastes rufus, is part of a deep-water (31–454 m) rockfish community that is fished commercially off California and has experienced population decline. This species is considered very difficult to age with traditional methods of counting growth increments in otolith cross-sections, creating the need to confirm age estimates with an independent, objective method. We measured the disequilibria of 210 Pb/ 226 Ra in S. rufus otoliths to compare with ages estimated from traditional methods. Radiometric ages corroborated mean otolith increment counts, with closest agreement for the oldest samples. We conclude that it is appropriate to use traditional cross-section methods to estimate age for S. rufus. Further, our results suggest longevity of 50 years or more for this deep-water rockfish. von Bertalanffy growth parameters calculated from these confirmed ages (with 95% confidence limits) were: L∞ = 488 mm (46.2) TL, K = 0.0482 (0.019), to = −8.372 (4.91), n = 81 males; L∞ = 594 mm (89.5) TL, K = 0.039 (0.018), to = −6.96 (4.97), n = 86 females. Comparison of age data from our study with length at maturity data from other researchers indicates that S. rufus reach sexual maturity at approximately 15 years of age. Like other deep-water members of this genus, S. rufus is slow growing and matures at an advanced age, important characteristics to consider for management of the species. Published by Elsevier B.V.

Validated age and growth estimates are important for constructing age-structured population dynamic models of chondrichthyan fishes, especially those which are exploited. We review age and growth studies of chondrichthyan fishes, using 28 recent studies to identify areas where improvements can be made in describing the characteristics of ageing structures (both traditional and novel) utilized to estimate ages of sharks, rays, and chimaeras. The topics identified that need consistency include the: (1) terminology used to describe growth features; (2) methods used to both verify and validate age estimates from chondrichthyan calcified structures, especially edge and marginal increment analyses; and (3) the functions used to produce and describe growth parameters, stressing the incorporation of size at birth (L 0) and multiple functions to characterize growth characteristics, age at maturity and longevity.

The white shark, Carcharodon carcharias, has a complex life history that is characterized by large scale movements and a highly variable diet. Estimates of age and growth for the white shark from the eastern North Pacific Ocean indicate they have a slow growth rate and a relatively high longevity. Age, growth, and longevity estimates useful for stock assessment and fishery models, however, require some form of validation. By counting vertebral growth band pairs, ages can be estimated, but because not all sharks deposit annual growth bands and many are not easily discernable, it is necessary to validate growth band periodicity with an independent method. Radiocarbon (14C) age validation uses the discrete 14C signal produced from thermonuclear testing in the 1950s and 1960s that is retained in skeletal structures as a time-specific marker. Growth band pairs in vertebrae, estimated as annual and spanning the 1930s to 1990s, were analyzed for Δ14C and stable carbon and nitrogen isotopes (δ 13C and δ 15N). The aim of this study was to evaluate the utility of 14C age validation for a wide-ranging species with a complex life history and to use stable isotope measurements in vertebrae as a means of resolving complexity introduced into the 14C chronology by ontogenetic shifts in diet and habitat. Stable isotopes provided useful trophic position information; however, validation of age estimates was confounded by what may have been some combination of the dietary source of carbon to the vertebrae, large-scale movement patterns, and steep 14C gradients with depth in the eastern North Pacific Ocean.

Age and growth estimates for the shortfin mako, Isurus oxyrinchus, derived from vertebral centra of 258 specimens (118 males, 140 females), ranging in size from 64 to 340 cm fork length (FL) were compared with data from 22 tag- recaptured individuals (74–193 cm FL) and length-frequency data from 1822 individuals (1035 males, 787 females; 65–215 cm FL). Annual bandpair deposition, confirmed by a concurrent bomb radiocarbon validation study, was used as the basis for band interpretation. Validation was further confirmed with a tetracycline-injected male shortfin mako recaptured after being at liberty off South Africa for 1 year and aged at 18 years. Growth rates from tag-recapture analysis (GROTAG) were higher than those derived from vertebral annuli and were only available from sharks up to 193 cm FL at recapture. Modal length-frequency data were used to verify the first four age classes. Growth curves were fit using both von Bertalanffy and Gompertz models. The 3-parameter version of the von Bertalanffy growth function produced the most biologically reasonable values for males, based on observed data (L ∞ = 253 cm FL, K = 0.125 year−1 (estimated longevity = 21 year), and L 0 = 72 cm). The 3-parameter version of the Gompertz growth function produced the most biologically reasonable estimates, for females (L ∞ = 366 cm FL, K = 0.087 year−1 (estimated longevity = 38 year) and L 0 = 88 cm. Males and females were aged to 29 (260 cm FL) and 32 years (335 cm FL), respectively. Both sexes grew similarly to age 11 (207 cm FL, 212 cm FL for males and females, respectively) when the curve leveled in males and continued to rise in females. Age at 50% maturity was estimated at 8 years for males (185 cm FL) and 18 years for females (275 cm FL). The species grows slower, matures later and has a longer life span than previously reported in North Atlantic waters.

Age estimation is an issue for the shortfin mako, Isurus oxyrinchus, because of dis- agreement on vertebral band-pair deposition periodicity. In the 1950s-1960s, thermonuclear testing released large amounts of radiocarbon into the atmosphere, which diffused into the ocean through gas exchange. This influx created a time-specific marker that can be used in age val- idation. Annual band-pair deposition in the por- beagle, Lamna nasus, was validated in a previous study and indicated preliminary annual deposi- tion in the shortfin mako, using four samples from one vertebra. In the present study, age estimates from 54 shortfin mako vertebrae collected in 1950-1984 ranged 1-31 years. Ageing error be- tween readers was consistent, with 76% of the estimates ranging within 2 years. Twenty-one D 14 C values from eight shortfin mako vertebrae (collected in the western North Atlantic in 1963- 1984) ranged -154.8& to 86.8&. The resulting conformity with the D 14 C timeline for the por- beagle supported annual band-pair deposition in vertebrae of the shortfin mako.

Increasing fishing pressure on sharks stocks over recent decades has resulted in declines of many populations and led to increasing concerns for their conservation. The extent of these declines, however, has been highly variable—the result of the level of fishing, ocean conditions, and the life history of individual species. Two recent articles have described the collapse and possible extirpation of shark populations in the northwest Atlantic Ocean and Gulf of Mexico. Herein, we examine the results of these two papers commenting on the data sets used, comparing them to other available data sets, and critically evaluating the analyses and conclusions. We argue that these conclusions have been overstated because: (1) the analyses were based on a limited number of data sets, (2) the data sets themselves are inadequate to describe the status of all shark populations in the northwest Atlantic Ocean and Gulf of Mexico reported in these studies, (3) available data sets that could produce different concl...

Spotted sand bass, Paralabrax maculatofasciatus, were collected from Bahia de Los Angeles, Baja California, Mexico covering as wide a size range as possible over four seasons (spring, summer, fall, and winter). Age was estimated and growth parameters calculated from growth zones counted in transverse otolith sections. An otolith edge analysis indicated an opaque growth zone was deposited once per year during the summer, validating the annual periodicity. Spotted sand bass from this region are fast growing with a relatively short life span of up to 11 years. Growth differs from the disjunct Pacific coast population by having a higher growth rate and a shorter longevity.

Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon (14C) signal that has provided a useful tracer and chronological marker in oceanic systems and organisms. The bomb-generated 14C signal retained in fish otoliths can be used as a time-specific recorder of the 14C present in ambient seawater, making it a useful tool in age validation of fishes. The goal of this study was to determine 14C in otoliths of the age-validated yelloweye rockfish (Sebastes ruberrimus) to establish a reference time series for the coastal waters of southeast Alaska. Radiocarbon values from the first year's growth of 43 yelloweye rockfish otoliths plotted against estimated birth year produced a 14C time series (1940–1990) for these waters. The initial rise of 14C occurred in 1958 and 14C levels rose to peak values (60–70‰) between 1966 and 1971, with a subsequent declining trend through the end of the record in 1990 (–3.2‰). In addition, the 14C data confirmed the longevity of the yelloweye rockfish to a minimum of 44 years and strongly support higher age estimates. This 14C time series will be useful for the interpretation of 14C accreted in biological samples from these waters.

Sustainable fisheries require (1) viable stock populations with appropriate harvest limits and (2) appropriate habitat for fish to survive, forage, seek refuge, grow and reproduce. Some deep-water habitats, such as those formed by deep-water stands of coral, may be vulnerable to fishing disturbance. The rate at which habitat can be restored is a critical aspect of fishery management. The purpose of this study was to characterize growth rates for a habitatforming deep-sea coral. Two nearly complete colonies of red tree coral (Primnoa resedaeformis) collected from waters off southeast Alaska were used for an analysis of age and growth characteristics. CAT scans revealed that colonies consisted of multiple settlement events, where older basal structures provided for settlement of new colonies. The decay of 210 Pb over the length of the colony was used to validate age estimates from growth ring counts. Age estimates were over 100 yr for sections near the heavily calcified base. Based on validated growth ring counts, growth of red tree coral ranged from 1.60 to 2.32 cm per year in height and was approximately 0.36 mm per year in diameter. These growth rates suggest that the fishery habitat created by red tree coral is extremely vulnerable to bottom fishing activities and may take over 100 years to recover.