Transactions of the American Fisheries SocietyVolume 145, Issue 4 p. 913-913 Article Hakes: Biology and Exploitation. Edited by H. Arancibia Wiley-Blackwell, Chichester, UK. 2015. 376 pages. $209.95 (hardcover), $167.99 (e-book) Guy W. Fleischer (retired), Guy W. Fleischer (retired) Alaska Fisheries Science Center, National Marine Fisheries Service, Seattle, Washington, USASearch for more papers by this author Guy W. Fleischer (retired), Guy W. Fleischer (retired) Alaska Fisheries Science Center, National Marine Fisheries Service, Seattle, Washington, USASearch for more papers by this author First published: 29 June 2016 https://doi.org/10.1080/00028487.2016.1194117Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume145, Issue4July 2016Pages 913-913 RelatedInformation

Pacific hake (Merluccius productus), also known as Pacific whiting, is the most abundant commercial fish species in the California Current Large Marine Ecosystem and is an important part of the ecosystem as both predator and prey. A large migratory population occurs off California, Oregon and Washington in the U.S. waters and off British Columbia in Canadian waters. Smaller distinct non-migratory populations of Pacific hake occur in major inlets of the northeast Pacific Ocean, including the Strait of Georgia and Puget Sound. The coastal Pacific hake population has supported a fishery averaging 222,000 t per year since 1966. Coastal Pacific hake migrate to northern feeding areas in the summer and southern spawning areas in the winter. The extent of the northern migration and the distribution along the coast are related to the population age and size composition and to varying ocean-climatic conditions, which also influence the growth and location of spawning aggregations. Pacific hake have a lifespan of about 20 years, reach maturity at about 4 years and achieve an average asymptotic size of 53 cm. Coastal Pacific hake are managed under the auspices of a treaty between the United States and Canada, and the two countries jointly conduct acoustic surveys of the resource, stock assessments, stock assessment reviews and management meetings. Prior to the treaty, there were independent and competing stock assessments from the United States and Canada. The Hake Treaty established a default harvest policy, a fixed harvest allocation for each country and a Joint Management Committee that determines the annual coast-wide total allowable catch on the basis of the best available science, the treaty's default harvest policy and input from industry advisors. Regulation and management of the individual fisheries continue to rest within each country. The fishery is executed by four sectors in the United States: vessels that deliver to shore-based processors, vessels that deliver to at-sea processors (mother ships), vessels that both catch and process at-sea (catcher-processors) and a tribal fishery. The Canadian fishery is prosecuted by vessels that deliver to shore-based processors, with a joint-venture mother ship sector in some years. The Pacific hake fishery in the United States and Canada is jointly certified by the Marine Stewardship Council as a sustainable fishery. Pacific hake must be frozen or processed soon after harvest to achieve a marketable product. Currently, most Pacific hake are marketed as fillets or headed and gutted products, although previously a large portion of the harvest was turned into surimi. While none of these products demands a high price, the total revenue to the industry is in tens of millions of U.S. dollars.

The widow rockfish (Sebastes entomelas) inhabits the continental shelf and upper slope of the west coast of North America. The U.S. west coast widow rockfish stock has declined since the mid-1980s, leading to implementation of increasingly stringent management restrictions upon the commercial fishery. The low numbers, patchy distribution, and preference for rocky habitats of the widow rockfish make this stock difficult to monitor using standard bottom trawl survey techniques and commercial landings data; currently, there is no reliable index of abundance. An ad hoc government-industry working group began meeting in 2004 to devise a new stock assessment survey strategy. The proposed strategy utilized local fishermen's knowledge of widow rockfish distribution and behavior, chartered commercial fishing vessels, and a combination of fisheries acoustics and underwater video sampling techniques. Results are presented from fieldwork conducted at three study sites off the central coast of Oregon, USA, in March 2005. Acoustic backscatter at 38kHz between 50m from the surface to 15m off the bottom was attributed primarily to widow rockfish. This classification was based on historical widow rockfish distribution at these sites, fish school appearance on acoustic echograms, and deployments of an underwater camera sled. Repeated acoustic sampling along predetermined transects spaced at 0.3nmi (0.56km) at two of the study sites documented the temporal and spatial variability of widow rockfish schools over the course of a single day and week-to-week. The CVs of average vertically integrated acoustic backscatter measured in repeated sampling passes at these two sites were 0.31 and 0.36, which are not unreasonable values for a fisheries survey time series. Fine-scale acoustic sampling at a total of three study sites showed that the spatial scale (horizontal dimensions) of the groups of widow rockfish schools observed ranged from 0.2 to 0.8nmi (0.37–1.48km). This study demonstrates that sampling of a coastwide suite of study sites selected using local fishermen's knowledge with a standard 38kHz scientific echosounder, supported by underwater video and limited midwater trawling, may be a promising way of monitoring U.S. west coast widow rockfish abundance. These techniques may also be relevant to monitoring other difficult-to-assess semi-dermersal species inhabiting rocky, untrawlable areas.

We compared the relative abundance of lake trout Salvelinus namaycush spawners in gill nets during fall 1999-2001 in Lake Michigan at 19 stocked spawning sites with that at 25 unstocked sites to evaluate how effective site-specific stocking was in recolonizing historically important spawning reefs. The abundance of adult fish was higher at stocked onshore and offshore sites than at unstocked sites. This suggests that site-specific stocking is more effective at establishing spawning aggregations than relying on the ability of hatchery-reared lake trout to find spawning reefs, especially those offshore. Spawner densities were generally too low and too young at most sites to expect significant natural reproduction. However, densities were sufficiently high at some sites for reproduction to occur and therefore the lack of recruitment was attributable to other factors. Less than 3% of all spawners could have been wild fish, which indicates that little natural reproduction occurred in past years. Wounding by sea lamprey Petromyzon marinus was generally lower for Seneca Lake strain fish and highest for strains from Lake Superior. Fish captured at offshore sites in southern Lake Michigan had the lowest probability of wounding, while fish at onshore sites in northern Lake Michigan had the highest probability. The relative survival of the Seneca Lake strain was higher than that of the Lewis Lake or the Marquette strains for the older year-classes examined. Survival differences among strains were less evident for younger year-classes. Recaptures of coded-wire-tagged fish of five strains indicated that most fish returned to their stocking site or to a nearby site and that dispersal from stocking sites during spawning was about 100 km. Restoration strategies should rely on site-specific stocking of lake trout strains with good survival at selected historically important offshore spawning sites to increase egg deposition and the probability of natural reproduction in Lake Michigan.

The USGS-Great Lakes Science Center has collected dreissenid mussels annually from Lake Michigan since zebra mussels (Dreissena polymorpha) became a significant portion of the bottomtrawl catch in 1999. For this study, we investigated dreissenid distribution, body mass, and recruitment at different depths in Lake Michigan during 2001–2003. The highest densities of dreissenid biomass were observed from depths of 27 to 46 m. The biomass of quagga mussels (Dreissena bugensis) increased exponentially during 2001–2003, while that of zebra mussels did not change significantly. Body mass (standardized for a given shell length) of both species was lowest from depths of 27 to 37m, highest from 55 to 64 m, and declined linearly at deeper depths during 2001–2003. Recruitment in 2003, as characterized by the proportion of mussels < 11 mm in the catch, varied with depth and lake region. For quagga mussels, recruitment declined linearly with depth, and was highest in northern Lake Michigan. For zebra mussels, recruitment generally declined non-linearly with depth, although the pattern was different for north, mid, and southern Lake Michigan. Our analyses suggest that quagga mussels could overtake zebra mussels and become the most abundant mollusk in terms of biomass in Lake Michigan.

Day 1 of the workshop was devoted to several lectures and shorter presentations by the participants. The lectures included three presentations on theory and techniques and four case studies (Great Lakes, Rivers, Lakes, Marine): Guy Fleischer, USGS-BRD, Ann Arbor, MI: Target strength of Great Lakes fishes John Horne: NOAA Great Lakes Laboratory, Ann Arbor, MI: Theoretical scattering models for predicting target strength and the choice of operating frequency: applications to alewife and smelt in the Great Lakes Patrick Sullivan, Cornell University, Ithaca NY: Survey design, introduction to the theory Doran Mason, Purdue University. Acoustics in Lake Superior. Kyle Hartman, West Virgnia University: Acoustics in riversthe Hudson experience Paul Walline, Lake Kinneret Laboratory, Israel: Acoustics in lakes the Lake Kinneret experience Fredrik Arrhenius, Marine Laboratory, Sweden. Acoustics in oceans -Atlantic herring in the Norwegian Sea.

Reliable estimates of fish biomass are vital to the management of aquatic ecosystems and their associated fisheries. Acoustic and midwater trawl surveys are an efficient sampling method for estimating fish biomass in large bodies of water. To improve the precision of biomass estimates from combined acoustic and midwater trawl surveys, sampling effort should be optimally allocated within each stage of the survey design. Based on information collected during fish surveys, we developed an approach to improve the design of combined acoustic and midwater trawl surveys through stratification. Geographic strata for acoustic surveying and depth strata for midwater trawling were defined using neighbor-restricted cluster analysis, and the optimal allocation of sampling effort for each was then determined. As an example, we applied this survey stratification approach to data from lakewide acoustic and midwater trawl surveys of Lake Michigan prey fishes. Precision of biomass estimates from surveys with and without geographic stratification was compared through resampling. Use of geographic stratification with optimal sampling allocation reduced the variance of Lake Michigan acoustic biomass estimates by 77%. Stratification and optimal allocation at each stage of an acoustic and midwater trawl survey should serve to reduce the variance of the resulting biomass estimates.

In the northern California Current, the onset of the 2005 upwelling season was five weeks later than usual, and well‐established upwelling with a cold surface signature did not occur until about seven weeks after this. As part of the joint US‐Canada Pacific hake survey, from 14–16 July 2005 we occupied the Newport Hydrographic line at 44.65°N, from the Oregon coast to 83 km offshore. Instead of the cold surface layer expected in July, we observed anomalously warm water. For example, 10‐m temperature at the shelf station NH‐5 was the warmest ever recorded in July at this location: 6.2°C above average, with observations back to 1961. We explore the pivotal role played by cumulative (time‐integrated) wind forcing in the development of upwelling, in both 2005 and previous years. We find that 80% of July surface layer (0–30 m) interannual temperature variance can be explained by cumulative upwelling index from the spring transition.

The relative quality of a habitat can influence fish consumption, growth, mortality, and production. In order to quantify habitat quality, several authors have combined bioenergetic and foraging models to generate spatially explicit estimates of fish growth rate potential (GRP). However, the capacity of GRP to reflect the spatial distributions of fishes over large areas has not been fully evaluated. We generated landscape scale estimates of steelhead (Oncorhynchus mykiss) GRP throughout Lake Michigan for 1994-1996, and used these estimates to test the hypotheses that GRP is a good predictor of spatial patterns of steelhead catch rates. We used surface temperatures (measured with AVHRR satellite imagery) and acoustically measured steelhead prey densities (alewife, Alosa pseudoharengus) as inputs for the GRP model. Our analyses demonstrate that potential steelhead growth rates in Lake Michigan are highly variable in both space and time. Steelhead GRP tended to increase with latitude, and mean GRP was much higher during September 1995, compared to 1994 and 1996. In addition, our study suggests that landscape scale measures of GRP are not good predictors of steelhead catch rates throughout Lake Michigan, but may provide an index of interannual variation in system-wide habitat quality.

Broadband acoustic echoes were collected on free-swimming alewives Alosa psuedoharungus, rainbow smelt Osmerus mordax, and bloaters Coregonus hoyi. Concurrent midwater trawls were used to determine species composition. A genetic neural network was trained on broadband echoes from each species to an overall correct classification rate of 91%. Tests of the trained network suggested an overall expected correct classification rate of 80-85% and indicated rainbow smelt and alewife echoes were less likely confused as compared to bloater. Application of the trained network to recorded echo data resulted in predicted species compositions that did not correspond well to those observed in the trawls. The classifiers may have been confounded by inclusion of echoes from various species, especially for bloater. A restriction to echoes collected concurrent to trawls or other controlled situations (e.g., pens or smaller lakes with single species) may be needed for building 'clean' classifiers.

Echo integration is a commonly used technique for assessment of fish stocks. In echo integration, a frequently used method to increase the signal-to-noise ratio is to ignore data below a set volume backscattering threshold. Although this form of thresholding is common, objective and replicable techniques for choosing this threshold are rarely used. Two opposing goals come into play when choosing an optimal threshold for estimating fish biomass using echo integration: maximizing the energy from backscatterers of interest, while simultaneously minimizing the energy from backscatterers not of interest. Both empirical and modeling techniques for choosing optimal thresholds were demonstrated using data from the 2003 integrated acoustic and trawl survey of Pacific hake. Empirical techniques were based on the receiver operating characteristic (ROC) curve. An ROC curve is a graphical plot of the number of true positives versus false positives for a binary classification system as the discrimination threshold is varied. Modeling techniques were based on volume backscattering data generated from modeled TS and density of hake and nonhake scatterers. For the case study using the 2003 Pacific hake survey, the historical threshold used for the southern portion of the survey was shown to be nonoptimal for that year.

A concurrent increase in lakewide abundance and decrease in size-at-age of bloater (Coregonus hoyi) in Lake Michigan have suggested density-dependent growth regulation. We investigated these temporal patterns by fitting a dynamic von Bertalanffy model and length–weight relationship with time-varying parameters to mean length- and weight-at-ages (ages 1–7) from annual surveys (1965–1999). We modeled yearling length, asymptotic size (L[Formula: see text]), and the parameters of a power relationship between mean weight and mean length (α and β) as changing slowly over time using a random walk model. The Brody growth coefficient (k) was modeled as a linear function of L[Formula: see text] with year-specific random deviations. Our results support a positive relationship between L[Formula: see text] and k, indicating that under conditions supporting larger asymptotic lengths, individuals approach the asymptote more rapidly. We explored the relationship between year-specific growth parameters and indices of lakewide bloater abundance and found evidence of density-dependent growth. However, in the most recent years, L[Formula: see text] and yearling length have remained low in Lake Michigan despite low bloater abundances, suggesting the occurrence of a fundamental shift in the food web.

The Great Lakes Water Quality Agreement stipulates that the Governments of Canada and the United States are responsible for restoring and maintaining the chemical, physical and biological integrity of the waters of the Great Lakes Basin Ecosystem. Due to varying mandates and areas of expertise, monitoring to assess progress towards this objective is conducted by a multitude of Canadian and U.S. federal and provincial/state agencies, in cooperation with academia and regional authorities. This paper highlights selected long-term monitoring programs and discusses a number of documented ecological changes that indicate the present state of the open and nearshore waters of the Great Lakes.

Past research has demonstrated that the recruitment pattern of Lake Michigan bloaters (Coregonus hoyi) was best represented by a Beverton-Holt function during 1977-1983. In this present study, we re-assessed relations in bloater recruitment and investigated trends in sex ratio and mean length at age as they related to recent changes in bloater abundance. Bloaters were collected from 1973 to 1997 during lake-wide bottom-trawl surveys and in western Lake Michigan from 1980 to 1998 during graded-mesh gill-net surveys. Length, weight, age, sex, and maturity of bloaters were recorded. The relative abundance of females in the population increased throughout the past 10-15 years to more than 80% in 1997. Relative abundance of females in the population was inversely related to overall abundance during periods of increasing female dominance. Female dominance may be related to an increasingly older population, which resulted from low recruitment, and to the greater longevity of female bloaters. Mean length at age decreased steadily in the 1980s with increased bloater abundance. Bloater recruitment was density dependent and followed a Ricker-type stock-recruitment relation. Future research will focus on identifying other factors that influence bloater recruitment such as the effect of female dominance.

Herein, we document changes in the Lake Michigan food web between 1970 and 2000 and identify the factors responsible for these changes. Control of sea lamprey (Petromyzon marinus) and alewife (Alosa pseudoharengus) populations in Lake Michigan, beginning in the 1950s and 1960s, had profound effects on the food web. Recoveries of lake whitefish (Coregonus clupeaformis) and burbot (Lota lota) populations, as well as the buildup of salmonine populations, were attributable, at least in part, to sea lamprey control. Based on our analyses, predation by salmonines was primarily responsible for the reduction in alewife abundance during the 1970s and early 1980s. In turn, the decrease in alewife abundance likely contributed to recoveries of deepwater sculpin (Myoxocephalus thompsoni), yellow perch (Perca flavescens), and burbot populations during the 1970s and 1980s. Decrease in the abundance of all three dominant benthic macroinvertebrate groups, including Diporeia, oligochaetes, and sphaeriids, during the 1980s in nearshore waters ([Formula: see text]50 m deep) of Lake Michigan, was attributable to a decrease in primary production linked to a decline in phosphorus loadings. Continued decrease in Diporeia abundance during the 1990s was associated with the zebra mussel (Dreissena polymorpha) invasion, but specific mechanisms for zebra mussels affecting Diporeia abundance remain unidentified.

Omul, Coregonus autumnalis, are a commercially important coregonine fish from Lake Baikal, Siberia, Russia. In Lake Baikal, three morphotypes recognized by fishery experts occupy different zones in the lake; they are referred to as littoral, pelagic, and benthic. Expressed character divergence was supported by whole-body morphometric analysis, but it is not known whether discrete genetic differ- ences accompany the observed morphological variation. This study was designed to assess the genetic variation of three different omul morphotypes sampled from different locations in Lake Baikal that were segregated by morphotype in multivariate analysis. We surveyed genetic variation with restriction frag- ment length polymorphism analysis of specific gene loci amplified with the polymerase chain reaction. Sequence variation was localized in the mitochondrial control region. Though no discrete genetic mark- ers were found, there'is evidence of reproductive segregation by geographic location that corroborates geographic variation in morphological characters. The omul, Coregonus autumnalis migratorius (Georgi), is the most important fish in the Lake Baikal region, comprising a major portion of both commercial and subsistence fisheries for centuries. After decades of intense harvest, environmental modification, and technological improvements in harvest methods, omul population abundance began to decline sharply (SMIR- NOV 1992). Virtually all populations were considered endangered by the mid-1900s and the fishery was closed from 1969-1975. Today, omul account for approximately 50% of the annu- al harvested biomass in the lake; commercial and subsistence fisheries are supported by wild

The Great Lakes Science Center has conducted lake-wide bottom trawl surveys of the fish community in Lake Michigan each fall since 1973. These systematic surveys are performed at depths of 9 to 110 m at each of seven index sites around Lake Michigan. Zebra mussel (Dreissena polymorpha) popu lations have expanded to all survey locations and at a level to sufficiently contribute to the bottom trawl catches. The quagga (Dreissena bugensis), recently reported in Lake Michigan, was likely in the catches though not recognized. Dreissena spp. biomass ranged from about 0.6 to 15 kg/ha at the various sites in 1999. Dreissenid mussels were found at depths of 9 to 82 m, with their peak biomass at 27 to 46 m. The colonization of these exotic mussels has ecological implications as well as potential ramifications on the ability to sample fish consistently and effectively with bottom trawls in Lake Michigan.