J. Brodziak

University of Hawaii at Manoa, Marine Biology Graduate Program, Adjunct

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Abundance Trends and Fisheries for Highly Migratory Species in the Pacific Ocean

ABSTRACT We review abundance trends and fisheries for highly migratory tunas, billfishes, and sha... more ABSTRACT We review abundance trends and fisheries for highly migratory tunas, billfishes, and sharks in the Pacific. Following World War II, Japanese longline fleets increased fishing effort and expanded across the Pacific. Substantial increases in catches of tunas and tuna-like species occurred from 1950 to 2000. Target species changed through time as deep-set longline effort replaced shallow-set effort. This led to greater catches of bigeye tuna which is currently experiencing overfishing and approaching an overfished condition. There have also been changes in fishing fleets through time and in particular, purse seine effort now accounts for the vast majority of skipjack and yellowfin tuna catches. Despite vast increases in fishing effort directed at tunas, many stocks are fully exploited and are not depleted. Pacific bluefin tuna is an exception and is experiencing overfishing and is overfished. Bycatches of billfishes and sharks have also led to diverse trends in abundance. Some billfish stocks, e.g. striped marlin, have been overfished while others, e.g. swordfish are abundant. In contrast, many shark stocks, e.g. oceanic whitetip shark, have declined in abundance due to low fecundity and limited resilience to harvest although blue shark may be an exception to this pattern.

An evaluation of the consistency of age-structured assessment in the Northeast Region

December 1994The Northeast Fisheries Science Center Reference Documents are a series of informal ... more December 1994The Northeast Fisheries Science Center Reference Documents are a series of informal reports produced by the Center for timely transmission of results obtained through work at the various NEFSC labs. The documents are reviewed internally before publication, but are not considered formal literature. The National Marine Fisheries Service does not endorse any proprietary material, process, or product mentioned in these reports, To obtain additional copies of this report contact, Information

A method to assess squid fisheries in the north-west Atlantic

ICES Journal of Marine Science, 1993

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Pacific Islands Fisheries Science Center

Summer Flounder Working Group

October 1994The Northeast Fisheries Science Center Reference Documents are a series of informal r... more October 1994The Northeast Fisheries Science Center Reference Documents are a series of informal reports produced by the Center for timely transmission of results obtained through work at the various NEFSC labs. The documents are reviewed internally before publication. but are not considered formal literature. The National Marine Fisheries Service does not endorse any proprietary material, process, or product mentioned in these reports. To obtain additional copies of this report contact, Information

Estimating stock-recruitment steepness from life history information: A case study of north Pacific bluefin tuna, Thunnus orientalis

ABSTRACT

1.0 Background

Dealing with uncertainty in ecosystem models: The paradox of use for living marine resource management

Progress in Oceanography, 2012

To better manage living marine resources (LMRs), it has become clear that ecosystem-based fisheri... more To better manage living marine resources (LMRs), it has become clear that ecosystem-based fisheries management (EBFM) is a desired approach. To do EBFM, one of the key tools will be to use ecosystem models. To fully use ecosystem models and have their outputs adopted, there is an increasingly recognized need to address uncertainty associated with such modeling activities. Here we characterize uncertainty as applied to ecosystem models into six major factors, including: natural variability; observation error; inadequate communication among scientists, decision-makers and stakeholders; the structural complexity of the model(s) used; outcome uncertainty; and unclear management objectives. We then describe best practices to address each of these uncertainties as they particularly apply to ecosystem models being used in a LMR management context. We also present case studies to highlight examples of how these best practices have been implemented. Although we acknowledge that this work was compiled by ecosystem modelers in an LMR management context primarily for other ecosystem modelers, the principles and practices described herein are also germane for managers, stakeholders and other natural resource management communities. We conclude by emphasizing not only the need to address uncertainty in ecosystem models, but also the feasibility and benefits of doing so.

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Length Composition Comparisons of USA and Canadian Fishery Catches for Atlantic Cod, Haddock and Yellowtail Flounder

Document de référence 2006/02 Reference Document 2006/02 Ne pas citer sans autorisation des auteu... more

Unraveling the recruitment problem: A review of environmentally-informed forecasting and management strategy evaluation

Fisheries Research, 2019

Studies describing and hypothesizing the impact of climate change and environmental processes on ... more Studies describing and hypothesizing the impact of climate change and environmental processes on vital rates of fish stocks are increasing in frequency, and concomitant with that is interest in incorporating these processes in fish stock assessments and forecasting models. Previous research suggests that including environmental drivers of fish recruitment in forecasting is of limited value, concluding that forecasting improvements are minimal while potential spurious relationships were sufficient to advise against inclusion. This review evaluates progress in implementing environmental factors in stock-recruitment projections and Management Strategy Evaluations (MSEs), from the year 2000 through 2017, by reviewing studies that incorporate environmental processes into recruitment forecasting, full-cycle MSEs, or simulations investigating harvest control rules. The only successes identified were for species with a short pre-recruit survival window (e.g., opportunistic life-history strategy), where the abbreviated lifespan made it easier to identify one or a limited set of key drivers that directly impact dynamics. Autoregressive methods appeared to perform as well, if not better, for species with a longer pre-recruit survival window (e.g., seasonal, inter-annual) during which the environment could potentially exert influence. This review suggests that the inclusion of environmental drivers into assessments and forecasting is most likely to be successful for species with short pre-recruit survival windows (e.g., squid, sardine) and for those that have bottlenecks in their life history during which the environment can exert a well-defined pressure (e.g., anadromous fishes, those reliant on nursery areas). The effects of environment may be more complicated and variable for species with a longer pre-recruit survival window, reducing the ability to quantify environment-recruitment relationships. Species with more complex early life histories and longer pre-recruit survival windows would benefit from future research that focuses on relevant species-specific spatio-temporal scales to improve mechanistic understanding of abiotic-biotic interactions.

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Maximum Likelihood Estimation of Stock Composition

Stock Identification Methods, 2005

Publisher Summary Stock composition can be a significant uncertainty in the management of mixed-s... more Publisher Summary Stock composition can be a significant uncertainty in the management of mixed-stock fisheries of highly migratory or transboundary resources. When a mixture of stocks with different productivities is harvested together, stocks with low productivity may be overharvested. Conversely, forgone yield may be substantial for high-productivity stocks if mixed-stock fishing effort is set too low. In this context, mixed-stock fisheries are similar to multispecies fisheries where different life histories imply different target harvest rates across species. Last, allocation of harvest among user groups is often predicated upon knowing the stock composition of the catch. Measuring stock composition in mixed-stock fisheries is often more challenging than determining species composition in multispecies fisheries, since identifying species is generally much simpler than determining where fish come from. One of the key challenges to effective management of mixed-stock fisheries is estimation of the relative contribution of each stock to the harvest. Stock composition analysis uses either mark-recapture techniques or differences in the frequency distributions of population characteristics among stocks to estimate the composition of a mixture of stocks. For example, statistical analyses of allozyme frequency distributions have routinely been used to estimate the contribution of Pacific salmon stocks in mixed-stock ocean fisheries. Seasonal fluctuations in the spatial distribution of stocks along with changes in the magnitude and distribution of fishing effort can further complicate stock composition analysis.

Model selection for standardizing striped marlin catch-per-unit-effort in the Hawaii-based longline fishery

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Stock assessment of swordfish (Xiphias gladius) in the Eastern Pacific Ocean through 2012

Update of the Production Model Assessment of the Eastern Pacific Swordfish Stock (Xiphias gladius) in 2010

Status of the Bottomfish Resources of American Samoa, Guam, and Commonwealth of the Northern Mariana Islands, 2005

Status of the shortspine thornyhead (Sebastolobus alascanus) resource in 1998

An Assessment of the Risk of Archipelagic Overfishing for Alternative Total Allowable Catches of Deep-7 Bottomfish in the Main Hawaiian Islands Pacific Islands Fish

E. 1992b. Geographic variation in population genetic structure of Chinook salmon from California and Oregon

Status of the Pacific coast groundfish fishery through 1997 and recommended biological catches for 1998: stock assessment and fishery evaluation. Assessment of the Dover Sole stock for 1997

Assessment of haddock on eastern Georges Bank

Resume Haddock catches from eastern Georges Bank fluctuated around 5,000 t from 1985 to 1990. Und... more Resume Haddock catches from eastern Georges Bank fluctuated around 5,000 t from 1985 to 1990. Under restrictive management measures, combined Canada/USA catches declined from over 6,400 t in 1991 to a low of about 2,100 t in 1995, fluctuated between about 3,000 t and 4,000 t until 1999 and have since increased to about 7,500 1. Les prises d'aiglefin dans le secteur est du banc Georges ont fluctue autour de 5 000 t de 1985 a 1990. Sous le coup de mesures de gestion restrictives, les prises canado-americaines combinees ont chute, passant de plus de 6 400 t en 1991 a un creux d'environ 2 100 t en 1995, puis ont fluctue entre quelque 3 000 a 4 000 t jusqu'en 1999 pour ensuite augmenter, se situant depuis a quelque 7 500 t. Adult population biomass (ages 3+) has steadily increased from near an historical low of about 10,000 t in 1993 to about 78,000 t at the beginning of 2003 but remains below the average biomass during 1930-55. The recent increase was supported by improved recruitment in the 1990's. The 2000 year-class is estimated to be larger than the strong 1975 and 1978 yearclasses. The fishing mortality rate for fully recruited ages 4+ has consistently been below the threshold reference target (Fref) of 0.26 since 1995. Reduced fishing mortality and avoidance of small fish in the fisheries in recent years has resulted in increased survival of incoming yearclasses and greater abundance at older ages. La biomasse de la population d'adultes (3+ ans) a progressivement augmente, pour passer d'un creux presque historique d'environ 10000 t en 1993 a environ 78 000 t au debut de 2003, bien qu'elle demeure inferieure a la biomasse moyenne de la periode 1930-1955. Cette recente augmentation est imputable a l'amelioration du recrutement dans les annees 1990. La classe d'âge 2000 est estimee comme etant plus abondante que les fortes classes 1975 et 1978. Depuis 1995, le taux de mortalite par peche des classes de 4+ ans pleinement recrutees a regulierement ete inferieur au taux de reference cible (Fref) de 0,26. Le taux reduit de mortalite par peche et la protection des petits individus de la peche dans les dernieres annees ont resulte en un taux de survie accru des classes d'âge en voie de recrutement et une plus forte abondance de poissons plus âges. With an assumed total catch of 8,000 t in 2003, a combined Canada/USA catch of 8,000 t in 2004 would result in a low probability that the fishing mortality rate in 2004 will exceed Fref. At this yield, there is a negligible probability of achieving a 10% biomass increase from 2004 to 2005, due to the 2 weak incoming year-classes, 2001 and 2002, but there is a low probability that the biomass will fall below the median 2005 rebuilding biomass of 65,000 t. The population age structure shows good representation at all ages. A un niveau suppose de prises totales de 8 000 t en 2003, il est peu probable que des prises canado-americaines combinees de 8 000 t en 2004 resulteraient en un taux de mortalite par peche superieur a Fref cette annee-la. A ce niveau de rendement, la probabilite que la biomasse augmente de 10 % entre 2004 et 2005 est negligeable parce que les deux classes d'âge en voie d'etre recrutees, soit les classes 2001 et 2002, sont peu abondantes, mais il existe une faible probabilite que la biomasse diminuera, pour se situer en 2005 sous la biomasse mediane requise pour le retablissement du stock, soit 65 000 t. La structure des âges dans la population revele que ceux-ci sont tous bien representes.

J. Brodziak

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