Feeding ecology of broadbill swordfish (Xiphias gladius) in the California current

Funding: Support for our study includes salary funding from the NOAA Fisheries’ Office of Science and Technology and contract funds from the Cooperative Institute for Marine, Earth, and Atmospheric Systems. The National Observer Program within NOAA Fisheries’ Office of Science and Technology carried out sample collection. While the study fits the scope of work under the coauthors’ performance plans, they received no specific funding for this work. The funders had no role in study design, analysis, decision to publish, or preparation of the manuscript. Acknowledgments This work would not have been possible without the assistance and samples provided by the NMFS Southwest Region Fishery Observer Program and the participating drift gillnet fishermen. We thank several assistant volunteers who helped process the stomach samples. Alexandra Stohs provided research assistance. Mark Lowry, Eric Hochberg and John Hyde helped identify some prey specimens. John Field, Chugey Sepulveda and Scott Aalbers offered science feedback. Barbara Muhling helped create the map. Kristen Koch, Annie Yau, Brad Erisman, Heidi Dewar, Stephanie Flores, Crystal Dombrow, Elan Portner and Ruben Bergtraun provided useful comments on the draft. Debra Losey assisted with library research. We also thank Hiroshi Ohizumi and two anonymous reviewers for their careful critiques that helped improve the manuscript.Peer reviewedPublisher PD

National Oceanic and Atmospheric Administration Report 190

Abstract: Statistical guidelines are described for the development of a pilot scientific observer sampling program to collect turtle interactions data from the Hawaii longline fishery. The best available data are presented and potential sources of variability in longline turtle take rates are discussed. A stratified sampling design for a pilot survey is developed based on time and target species. An array of sample size choices for the pilot program is presented covering a range of tolerance levels and confidence levels for estimation of total turtle take

National Oceanic and Atmospheric Administration Report 344

Report on "estimate body size at sexual maturity for Hawaiian spiny lobster and slipper lobster using all available fishery independent research catch data from 1986 to 2001." (pg. 1

Length-based risk analysis for assessing sustainability of data-limited tropical reef fisheries

Abstract This study extended a “data-limited” length-based stock assessment approach to a risk analysis context. The estimation-simulation method used length frequencies as the principal data in lieu of catch and effort. Key developments were to: (i) incorporate probabilistic mortality and growth dynamics into a numerical cohort model; (ii) employ a precautionary approach for setting sustainability reference points for fishing mortality (FREF) and stock reproductive biomass (BREF); (iii) define sustainability risks in terms of probability distributions; and, (iv) evaluate exploitation status in terms of expected length frequencies, the main “observable” population metric. This refined length-based approach was applied to six principal exploited reef fish species in the Florida Keys region, consisting of three groupers (black grouper, red grouper, and coney), two snappers (mutton snapper and yellowtail snapper), and one wrasse (hogfish). The estimated sustainability risks for coney were low (<35%) in terms of benchmarks for fishing mortality rate and stock reproductive biomass. The other five species had estimated sustainability risks of greater than 95% for both benchmarks. The data-limited risk analysis methodology allowed for a fairly comprehensive probabilistic evaluation of sustainability status from species and community perspectives, and also a frame of reference for exploring management options balancing sustainability risks and fishery production

Length-Based Assessment of Coral Reef Fish Populations in the Main and Northwestern Hawaiian Islands

<div><p>The coral reef fish community of Hawaii is composed of hundreds of species, supports a multimillion dollar fishing and tourism industry, and is of great cultural importance to the local population. However, a major stock assessment of Hawaiian coral reef fish populations has not yet been conducted. Here we used the robust indicator variable “average length in the exploited phase of the population (</p><p></p><p></p><p><mi>L</mi><mo>¯</mo></p><p></p><p></p>)”, estimated from size composition data from commercial fisheries trip reports and fishery-independent diver surveys, to evaluate exploitation rates for 19 Hawaiian reef fishes. By and large, the average lengths obtained from diver surveys agreed well with those from commercial data. We used the estimated exploitation rates coupled with life history parameters synthesized from the literature to parameterize a numerical population model and generate stock sustainability metrics such as spawning potential ratios (SPR). We found good agreement between predicted average lengths in an unfished population (from our population model) and those observed from diver surveys in the largely unexploited Northwestern Hawaiian Islands. Of 19 exploited reef fish species assessed in the main Hawaiian Islands, 9 had SPRs close to or below the 30% overfishing threshold. In general, longer-lived species such as surgeonfishes, the redlip parrotfish (<i>Scarus rubroviolaceus</i>), and the gray snapper (<i>Aprion virescens</i>) had the lowest SPRs, while short-lived species such as goatfishes and jacks, as well as two invasive species (<i>Lutjanus kasmira</i> and <i>Cephalopholis argus</i>), had SPRs above the 30% threshold.<p></p></div

Feeding ecology of broadbill swordfish (Xiphias gladius) in the California current.

The feeding ecology of broadbill swordfish (Xiphias gladius) in the California Current was described based on analysis of stomach contents collected by fishery observers aboard commercial drift gillnet boats from 2007 to 2014. Prey were identified to the lowest taxonomic level and diet composition was analyzed using univariate and multivariate methods. Of 299 swordfish sampled (74 to 245 cm eye-to-fork length), 292 non-empty stomachs contained remains from 60 prey taxa. Genetic analyses were used to identify prey that could not be identified visually. Diet consisted mainly of cephalopods but also included epipelagic and mesopelagic teleosts. Jumbo squid (Dosidicus gigas) and Gonatopsis borealis were the most important prey based on the geometric index of importance. Swordfish diet varied with body size, location and year. Jumbo squid, Gonatus spp. and Pacific hake (Merluccius productus) were more important for larger swordfish, reflecting the ability of larger specimens to catch large prey. Jumbo squid, Gonatus spp. and market squid (Doryteuthis opalescens) were more important in inshore waters, while G. borealis and Pacific hake predominated offshore. Jumbo squid was more important in 2007-2010 than in 2011-2014, with Pacific hake being the most important prey item in the latter period. Diet variation by area and year probably reflects differences in swordfish preference, prey availability, prey distribution, and prey abundance. The range expansion of jumbo squid that occurred during the first decade of this century may particularly explain their prominence in swordfish diet during 2007-2010. Some factors (swordfish size, area, time period, sea surface temperature) that may influence dietary variation in swordfish were identified. Standardizing methods could make future studies more comparable for conservation monitoring purposes

Example of yield-per-recruit isopleths.

<p>Yield as a function of fishing mortality rates (F) and sizes at first capture (<i>L</i>_<i>c</i>) for the giant trevally <i>Caranx ignobilis</i>. <i>Y</i>_curr represents current yield-per-recruit (in kg) in the fishery and <i>Y</i>_eum is the highest possible yield for the current <i>F</i> (0.4). The gray area represents combinations of <i>F</i> and <i>L</i>_<i>c</i> that result in SPRs below 30%. <i>L</i>_<i>c</i> eum is the minimum size limit that will maximize yield while <i>L</i>_<i>c</i> SPR30 is the minimum size limit that will lead to an SPR of 30% given the current <i>F</i>.</p

Average length comparisons.

<p>(A) Comparison of average lengths in the commercial dataset versus the underwater visual survey dataset for the main Hawaiian Islands (MHI). Closed circles represent average lengths by species in different subregions of the MHI. (B) Average lengths observed in the Northwestern Hawaiian Islands versus simulated unexploited (pristine) average lengths. The red line represents perfect agreement between the two sets of average lengths. Species codes are defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133960#pone.0133960.t002" target="_blank">Table 2</a>.</p