Fisheries Oceanography最新文献

The distribution of marine species is changing as a direct result of climate change. Large pelagic highly migratory species (HMS), like tunas, billfishes, and sharks, are particularly sensitive to environmental change due to their migratory nature and use of large-scale ocean features. These temporal and spatial shifts are likely reflected in the Atlantic HMS recreational fishery and could have downstream effects on coastal communities. We utilized dockside intercept data from the Large Pelagics Survey (LPS) from 2002 to 2019, which conducts sampling from June to October and spans Maine to Virginia, USA. We assessed how species catch composition has changed and developed spatiotemporal models to understand latitudinal and temporal shifts in the recreational catch of 12 HMS groups. Latitudinal shifts were significantly affected by Northeast Shelf SST for 11 of the 12 HMS groups and ranged from 3 ± 1 km°C⁻¹ for the large bluefin tuna to 40 ± 1 km°C⁻¹ for the blue shark. In addition, the estimated day of the year when the first 25% of bigeye tuna intercepts occurred, happened over 50 days earlier in 2019 compared to 2002, suggesting the initial catch is happening earlier in recent years. These results suggest that changes in species distribution and phenology are affecting where and when HMS recreational catch occurs. Understanding these shifts would allow managers to be more responsive and flexible and also help communities prepare for changes, whether it would be a switch to a new species or shifts in the fishing season.

Anadromous fishes, such as Pacific salmon, spend portions of their life cycle in freshwater and marine systems, thus rendering them susceptible to a variety of natural and anthropogenic stressors. These stressors operate at different spatiotemporal scales, whereby freshwater conditions are more likely to impact single populations or subpopulations, while marine conditions are more likely to act on entire evolutionarily significant units (ESUs). Coherence in population parameters like survival and productivity can therefore serve as an indicator of relative influence. The goal of this study was to elucidate scale-dependent shifts in Oregon Coast coho salmon productivity. We used a multivariate state-space approach to analyze almost 60 years of stock-recruitment data for the Oregon Coast ESU. Analyses were conducted separately for time periods prior to and after 1990 to account for improvements in abundance estimation methods and significant changes in conservation and management strategies. Prior to 1990, productivity declined for most Oregon Coast populations, especially through the 1980s. From 1990–onward, coherence increased, and trends tracked closely with the North Pacific Gyre Oscillation (NPGO). The latter period is associated with reductions in harvest rates and hatchery production such that the relative influence of the marine environment may have grown more apparent following the removal of these stressors. Furthermore, the link between productivity and NPGO is consistent with trends observed for several other Pacific salmon ESUs. If Oregon Coast coho salmon populations become more synchronous, managers can expect to face new challenges driven by reductions in the population portfolio effect and increasingly variable marine conditions due to climate change.

To understand the spatio-temporal dynamics of juvenile chum salmon Oncorhynchus keta and their zooplankton prey, the neritic Pseudocalanus newmani, the oceanic Eucalanus bungii, and Themisto japonica, we developed species-specific environmental DNA (eDNA) quantification methods. First, we confirmed that juvenile chum salmon collected in Otsuchi Bay preyed on the target zooplankton by the stomach contents analyses using the developed assays. Size-fraction analyses of the water collected in the bay showed that P. newmani and E. bungii DNA were derived mostly from nauplii and early copepodids. We then investigated the distribution and abundance of zooplankton and juvenile chum salmon in Otsuchi Bay using eDNA analyses of the same water samples collected from January to June in 2018 and 2019. Chum salmon DNA was found in the bay from the end of January to mid-June. P. newmani DNA appeared across the bay throughout the season and were most abundant from February to May, while the other two species DNA were only found in spots, in lower quantities, from March to May. The timings that the zooplankton DNA quantities became greater were corresponded well to that of the Oyashio water intrusion into the bay. In addition, the environmental data indicates that P. newmani was possibly transported also by the Coastal Oyashio water in 2019. The present study successfully revealed species-specific patterns in the dynamics of zooplankton and chum salmon, reflecting their ecological characteristics and oceanographic conditions, and showed the effectiveness of simultaneous eDNA quantifications for diverse taxa from the same water samples.

Fall is an important time of year for fish recruitment in the Gulf of Mexico, with many commercially and recreationally important species spawning during this period. Changes in temperature and salinity regimes through seasonally abnormal freshwater input may change spawning patterns and displace larvae. Such an event occurred off the coast of Galveston Bay, Texas, when a freshwater flood plume formed from unprecedented rainfall related to Hurricane Harvey at the end of August 2017. This study investigated the effects of a large-scale flood plume on larval fish assemblages, collected at nearshore and shelf zones 1 and 2 months after Hurricane Harvey. Samples from 2017 were compared to historical datasets collected by NOAA Fisheries in September (2000–2004 and 2006–2016) and October (2000–2012). Evidence of lowered water temperature and salinity was found in both September and October 2017. Larval community composition changed along cross-shelf gradients and with increasing distance from shore. We also found evidence of 2017 assemblages differing from historical data, with the September 2017 assemblage more closely resembling those from October historical samples. Observed differences in 2017 assemblages were most likely explained by an earlier onset in fall sciaenid spawning, suggesting that decreases in water temperature occurring during hurricanes have the potential to alter fish spawning patterns.

Understanding the influence of ocean conditions on predator–prey relationships can provide insight for ecosystem-based fisheries management. Pacific hake (Merluccius productus) are abundant and commercially important groundfish in the California Current Ecosystem (CCE) that consume euphausiids (krill) as a major prey item. We used data from the biennial joint U.S.-Canada Integrated Ecosystem & Acoustic Trawl Survey for Pacific hake (2007–2019, n = 8 surveys) to quantify co-occurrence of age 2+ hake with krill in relation to bottom depth, continental shelf break location, surface chlorophyll-a, and 100-m temperature. Vertical distributions of hake varied among years and were not correlated to krill depth. Hake hotspots occurred primarily off the Oregon coast and near Cape Mendocino, while most krill hotspots occurred in the northern CCE. The probability of co-occurrence was greatest during cool ocean conditions (100-m temperature 1°C below average), averaging 41.0% and extending throughout most of the CCE. During warm ocean conditions (100-m temperature 1°C above average), predicted co-occurrence averaged 17.0% and was concentrated near Cape Mendocino. These results indicate that hake-krill co-occurrence is a function of predator and prey spatial distributions and overall krill abundance. Furthermore, temperature influences hake-krill co-occurrence and may explain some of the variation in hake growth and recruitment to the fishery.

Diamond squid Thysanoteuthis rhombus (Troschel, 1857), which can grow to a dorsal mantle length of ~100 cm in 1 year, is an important fisheries resource in subtropical and temperate waters worldwide. Around Japan, it is an important resource in the East China Sea, Sea of Japan, and western North Pacific Subtropical Gyre, including the Kuroshio area. It is not known if linkages occur between these habitats. To clarify the species distribution, we estimated the habitat of young squid using a generalized additive model based on trawl surveys and analyzed carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N) in tissue samples. Based on trawl observations, young squid were distributed around northeastern Taiwan and the Okinawa Islands in June–July and in the Sea of Japan and the Kuroshio extension areas in August–September. We observed ontogenetic changes in the stable isotope ratios. The δ¹⁵N values in large diamond squid (dorsal mantle length > 400 mm) were significantly lower in the Pacific than those in other areas. Considering that the δ¹⁵N of forage fish is low in the Pacific and high in the East China Sea and Sea of Japan, large diamond squid in the northwest Pacific presumably have two distinct habitats.

During the 1990s, coastal habitat off southeastern Massachusetts (SEMA) supported commercially viable fisheries for American lobster (Homarus americanus). Over the past two decades, landings and post-larval settlement of lobsters in this region, which is near the southern edge of the species' range, have declined substantially, concurrent with a period of significant warming of the coastal waters off southern New England. Previous work has suggested that rising ocean temperatures may adversely impact the survival of larval and early benthic phase (EBP) lobsters and may cause adult lobsters to seek cooler offshore waters during the critical time of larval release. To investigate the manner in which the observed decline in lobster abundance may be linked to warming coastal waters, a high-resolution hydrodynamic model was used to quantify the increase in water temperature experienced by EBP lobster off SEMA and to supply input to an individual-based model of lobster larval transport from release areas delineated using fishery-dependent data of late-stage egg-bearing lobsters. The results indicate that rising coastal water temperatures may have adversely impacted EBP lobster recruitment off SEMA by (1) causing an offshore shift in the area of larval release that resulted in a reduction in the delivery of larvae to suitable nearshore EBP habitat and (2) dramatically increasing thermal stress experienced by recently settled EBP lobsters. These findings highlight the implications of warming coastal waters on southern New England lobster population connectivity and provide insight to an understudied mechanism by which climate change affects marine species recruitment.

Interdisciplinary data fuel fisheries oceanography research and the ecosystem-based approaches to management and sustainable development it informs. Underlying this is a distributed ocean observing framework that is integrated, interoperable, interactive, and accessible. In recognition of the 30th anniversary of Fisheries Oceanography the journal, this paper reviews the evolution of observing instruments and platforms used in contemporary fisheries oceanography the science. Illustrated with personal anecdotes, past efforts to create or adopt observing technologies, and examples of their use in research, this highlights the spectrum of instruments, systems, and programs used to survey and monitor ocean ecosystems. Modern ocean observing systems are complex and varied, reflecting the range and diversity of data required by fisheries oceanographers. These systems require a large and ongoing investment and an interdisciplinary community of scientists, engineers, and technicians to design, build, install, operate, and maintain them. Common themes emerge from a review of past successful instrument R&D and deployments. It is a highly collaborative, integrative, and iterative process. Most systems are the result of vision, planning, and perseverance, backed by careful calibration and intercomparison. Long-term support is essential; public–private partnerships that leverage funding, technology, and infrastructure are critical. Sustaining long time series for monitoring population and ecosystem change and to support fisheries oceanography research is a priority. Future areas of focus include continuously innovating and updating technologies, implementing a backbone of core observations, and maintaining a nimble infrastructure and R&D capacity to seize new opportunities and address emerging challenges.

Johan Hjort's “critical period” hypothesis, which postulates that year-class strength is determined in the short period following the onset of exogenous feeding, has rarely been supported by empirical data. Instead, the current understanding is that recruitment is determined by cumulative mortality throughout early life. Recent studies relied on the measure of growth autocorrelation derived from otolith daily increment widths to test the link between growth rate achieved during the post-hatch period and during subsequent phases of the larval stage. Based on this approach, we revisit the role of larval growth in driving survival potential in three clupeoid species: Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, and Pacific round herring Etrumeus micropus throughout the larval stage, using a combination of published datasets of otolith increment widths. Strong growth autocorrelation was detected for all three species throughout the larval stage, suggesting that initial growth determines to some extent growth rates achieved later in life. The extent of autocorrelation was reduced in sardine relative to anchovy and round herring at older ages. This interspecific difference could be attributed to differences in sensitivity to variability of environmental factors such as water temperature and food availability. The present findings suggest that the effect of early growth rate persists into later life stages for driving survival potential, which could reconcile the classic concept of “critical period” and the current “growth–survival” paradigm.

Estimating demographic changes in a population requires the measurement of some minimal combination of several vital rates, including the flux of individuals into a population, the population growth rate, individual growth rates and mortality rates. For larval fishes, the ratio of instantaneous mortality to growth (i.e., their ‘recruitment potential’) has been used to make inferences of cohort trajectory where measures of population growth rates are not attainable. Attaining estimates of mortality and growth is an arduous task, and use of the recruitment potential metric has been limited. Here, we relate size spectra of the broader plankton community to the recruitment potential of simultaneously sampled larval Pacific sardines (Sardinops sagax), from three voyages off eastern Australia. As the size structure of a population is determined by the ratio of mortality to growth, and there is remarkable consistency in size spectra across ecosystems, we test the hypothesis that the recruitment potential of larval fish is reflected in community-level measures of plankton size spectra. Contrary to expectations, results from this study demonstrate a negative relationship between the slope of the plankton size spectra and the recruitment potential of larval Pacific sardine. However, we also demonstrate several other stronger relationships between recruitment potential and physical oceanographic parameters. Together, results suggest plankton size spectra are unlikely to reflect recruitment potential directly. Incorporating some size-based aspects of the plankton community into a broader modelling framework with a range of oceanographic parameters could further our ability to determine how larval success varies across a seascape.