Marine Mammal Interactions Research Articles

Marine Mammal Interactions With Fisheries: Review of Research and Management Trends Across Commercial and Small-Scale Fisheries

Marine mammal interactions with fisheries, such as bycatch and depredation, are a common occurrence across commercial and small-scale fisheries. We conducted a systematic review to assess the management responses to marine mammal interactions with fisheries. We analyzed literature between 1995 and 2021 to measure research trends in studies on direct and indirect interactions for: (i) high and low to middle-income countries, (ii) fishery operations (commercial and small-scale), and (iii) taxonomic groups. Management responses were categorized using the framework described previously in peer-reviewed studies. Marine mammal bycatch remains a major conservation concern, followed by marine mammal depredation of fishing gear. A high proportion of studies concentrated on commercial fisheries in high-income countries, with an increase in small-scale fisheries in low to middle-income countries between 1999 and 2020. The insufficient understanding of the social dimensions of interactions and the inevitable uncertainties concerning animal and human behaviors are major challenges to effective management. Despite the key role of human behavior and socioeconomics, we found only eight articles that incorporate human dimensions in the management context. Integrating social dimensions of marine mammal interactions with fisheries could help in setting pragmatic conservation priorities based on enhanced understanding of critical knowledge gaps. An area-specific adaptive management framework could be an effective tool in reducing the risk to marine mammals from fisheries by coupling technical solutions with socio-economic and political interventions. We conclude that despite the vast body of literature on this subject, a “silver bullet” management solution to marine mammal interactions with fisheries does not yet exist.

Long-Term Patterns of Noise From Underwater Explosions and Their Relation to Fisheries in Southern California

Acoustic deterrents can reduce marine mammal interactions with fisheries and aquacultures, but they contribute to an increasing level of underwater noise. In Southern California, commercially produced explosive deterrents, commonly known as “seal bombs,” are used to protect fishing gear and catch from pinniped predation, which can cause extensive economic losses for the fishing community. Passive acoustic monitoring data collected between 2005 and 2016 at multiple sites within the Southern California Bight and near Monterey Bay revealed high numbers of these small-charge underwater explosions, long-term, spatio-temporal patterns in their occurrence, and their relation to different commercial purse-seine fishing sectors. The vast majority of explosions occurred at nighttime and at many nearshore sites high explosion counts were detected, up to 2,800/day. Received sound exposure levels of up to 189 dB re 1 μPa2-s indicate the potential for negative effects on marine life, especially in combination with the persistence of recurring explosions during periods of peak occurrence. Due to the highly significant correlation and similar spatio-temporal patterns of market squid landings and explosion occurrence at many sites, we conclude that the majority of the recorded explosions come from seal bombs being used by the California market squid purse-seine fishery. Additionally, seal bomb use declined over the years of the study, potentially due to a combination of reduced availability of market squid driven by warm water events in California and regulation enforcement. This study is the first to provide results on the distribution and origin of underwater explosions off Southern California, but there is a substantial need for further research on seal bomb use in more recent years and their effects on marine life, as well as for establishing environmental regulations on their use as a deterrent.

Technical mitigation to reduce marine mammal bycatch and entanglement in commercial fishing gear: lessons learnt and future directions

Fisheries bycatch is one of the biggest threats to marine mammal populations. A literature review was undertaken to provide a comprehensive assessment and synopsis of gear modifications and technical devices to reduce marine mammal bycatch in commercial trawl, purse seine, longline, gillnet and pot/trap fisheries. Successfully implemented mitigation measures include acoustic deterrent devices (pingers) which reduced the bycatch of some small cetacean species in gillnets, appropriately designed exclusion devices which reduced pinniped bycatch in some trawl fisheries, and various pot/trap guard designs that reduced marine mammal entrapment. However, substantial development and research of mitigation options is required to address the bycatch of a range of species in many fisheries. No reliably effective technical solutions to reduce small cetacean bycatch in trawl nets are available, although loud pingers have shown potential. There are currently no technical options that effectively reduce marine mammal interactions in longline fisheries, although development of catch and hook protection devices is promising. Solutions are also needed for species, particularly pinnipeds and small cetaceans, that are not deterred by pingers and continue to be caught in static gillnets. Large whale entanglements in static gear, particularly buoy lines for pots/traps, needs urgent attention although there is encouraging research on rope-less pot/trap systems and identification of rope colours that are more detectable to whale species. Future mitigation development and deployment requires rigorous scientific testing to determine if significant bycatch reduction has been achieved, as well as consideration of potentially conflicting mitigation outcomes if multiple species are impacted by a fishery.

Killer whale (Orcinus orca) interactions with blue-eye trevalla (Hyperoglyphe antarctica) longline fisheries.

Over the past five decades, marine mammal interactions with fisheries have become a major human-wildlife conflict globally. The emergence of longline fishing is concomitant with the development of depredation-type interactions i.e., marine mammals feeding on fish caught on hooks. The killer whale (Orcinus orca) is one of the species most involved in depredation on longline fisheries. The issue was first reported in high latitudes but, with increasing expansion of this fishing method, other fisheries have begun to experience interactions. The present study investigated killer whale interactions with two geographically isolated blue-eye trevalla (Hyperoglyphe antarctica) fisheries operating in temperate waters off Amsterdam/St. Paul Islands (Indian Ocean) and south-eastern Australia. These two fisheries differ in the fishing technique used (vertical vs. demersal longlines), effort, catch, fleet size and fishing area size. Using 7-year (2010–16) long fishing and observation datasets, this study estimated the levels of killer whale interactions and examined the influence of spatio-temporal and operational variables on the probability of vessels to experience interactions. Killer whales interactions occurred during 58.4% and 21.2% of all fishing days, and over 94% and 47.4% of the fishing area for both fisheries, respectively. In south-eastern Australia, the probability of occurrence of killer whale interactions during fishing days varied seasonally with a decrease in spring, increased with the daily fishing effort and decreased with the distance travelled by the vessel between fishing days. In Amsterdam/St. Paul, this probability was only influenced by latitude, with an increase in the southern part of the area. Together, these findings document two previously unreported cases of high killer whale depredation, and provide insights on ways to avoid the issue. The study also emphasizes the need to further examine the local characteristics of fisheries and the ecology of local depredating killer whale populations in as important drivers of depredation.

Mitigating cetacean bycatch in coastal Ecuador: Governance challenges for small-scale fisheries

Bycatch of marine fauna by small-scale (artisanal) fisheries is an important anthropogenic mortality source to several species of cetaceans, including humpback whales and odontocetes, in Ecuador's marine waters. Long-term monitoring actions and varied conservation efforts have been conducted by non-governmental organizations along the Ecuadorian coast, pointing toward the need for a concerted mitigation plan and actions to hamper cetaceans’ bycatch. Nevertheless, little has currently been done by the government and regional authorities to address marine mammal interactions with fisheries in eastern Pacific Ocean artisanal fisheries. This study provides a review of Ecuador's current status concerning cetacean bycatch, and explores the strengths and weaknesses of past and current programs aiming to tackle the challenges of bycatch mitigation. To bolster our appraisal of the policies, a synthesis of fishers’ perceptions of the bycatch problem is presented in concert with recommendations for fostering fishing community-based conservation practices integrated with policies to mitigate cetacean bycatch. Our appraisal, based upon the existing literature, indicates a situation of increasing urgency. Taking into consideration the fishers’ perceptions and attitudes, fisheries governance in Ecuador should draw inspiration from a truly bottom-up, participatory framework based on stakeholder engagement processes; if it is based on a top-down, regulatory approach, it is less likely to succeed. To carry out this process, a community-based conservation programs to provide conditions for empowering fishing communities is recommend. This would serve as an initial governance framework for fishery policy for conserving marine mammals while maximizing the economic benefits from sustainable small-scale fisheries in Ecuador.

Southeast Alaska Sperm Whale Avoidance Project (SEASWAP): a successful collaboration among scientists and industry to study depredation in Alaskan waters

AbstractIn Alaskan waters, depredation on sablefish longline gear by sperm whales increases harvesting cost, negatively biases stock assessments, and presents a risk of entanglement for whales. The Southeast Alaska Sperm Whale Avoidance Project (SEASWAP), a collaborative effort involving industry, scientists, and managers, since 2003 has undertaken research to evaluate depredation with a goal of recommending measures to reduce interactions. Prior to 2003, little was known about sperm whale distribution and behaviour in the Gulf of Alaska (GOA). Although fishers were reporting increasing interactions, the level of depredation varied with no apparent predictor of occurrence across vessels. Between 2003 and 2007, fishers were provided with fishery logbooks and recorded information on whale behaviour, whale presence and absence, during the set, soak, and haul for 319 sets in the GOA. Data were evaluated for a vessel, area, and seasonal (month) effect in the presence and absence of sperm whales. Using catch per unit effort (cpue) as a metric, in kg/100 hooks, results indicated that depredation depended on both the vessel and the area. More whales associated with vessels from April to August. Sperm whales were also likely to be present when cpue was high, revealing that whales and fishers both knew the most productive fishing areas, but confounding the use of cpue as a metric for depredation. Using a Bayesian mark-recapture analysis and the sightings histories of photo-identified whales, an estimated Nˆ=135 (95% CI 124, 153) sperm whales were associating with vessels in 2014. A spatial model was fitted to 319 longline sets and quantified a 3% loss in cpue, comparable to other global studies on sperm whale depredation. Through all phases of SEASWAP, our understanding of depredation has gained significantly. This successful collaboration should be considered as a model to create partnerships and build collaborations between researchers and fisherpeople encountering marine mammal interactions with fishing gear.

The impact of predation by marine mammals on patagonian toothfish longline fisheries.

Predatory interaction of marine mammals with longline fisheries is observed globally, leading to partial or complete loss of the catch and in some parts of the world to considerable financial loss. Depredation can also create additional unrecorded fishing mortality of a stock and has the potential to introduce bias to stock assessments. Here we aim to characterise depredation in the Patagonian toothfish (Dissostichus eleginoides) fishery around South Georgia focusing on the spatio-temporal component of these interactions. Antarctic fur seals (Arctocephalus gazella), sperm whales (Physeter macrocephalus), and orcas (Orcinus orca) frequently feed on fish hooked on longlines around South Georgia. A third of longlines encounter sperm whales, but loss of catch due to sperm whales is insignificant when compared to that due to orcas, which interact with only 5% of longlines but can take more than half of the catch in some cases. Orca depredation around South Georgia is spatially limited and focused in areas of putative migration routes, and the impact is compounded as a result of the fishery also concentrating in those areas at those times. Understanding the seasonal behaviour of orcas and the spatial and temporal distribution of “depredation hot spots” can reduce marine mammal interactions, will improve assessment and management of the stock and contribute to increased operational efficiency of the fishery. Such information is valuable in the effort to resolve the human-mammal conflict for resources.

Interactions of marine mammals and birds with offshore membrane enclosures for growing algae (OMEGA)

BackgroundOMEGA is an integrated aquatic system to produce biofuels, treat and recycle wastewater, capture CO2, and expand aquaculture production. This system includes floating photobioreactors (PBRs) that will cover hundreds of hectares in marine bays. To assess the interactions of marine mammals and birds with PBRs, 9 × 1.3 m flat panel and 9.5 × 0.2 m tubular PBRs were deployed in a harbor and monitored day and night from October 10, 2011 to Janurary 22, 2012 using infrared video. To observe interactions with pinnipeds, two trained sea lions (Zalophus californianus) and one trained harbor seal (Phoca vitulina richardii) were observed and directed to interact with PBRs in tanks. To determine the forces required to puncture PBR plastic and the effects of weathering, Instron measurements were made with a sea otter (Enhydra lutris) tooth and bird beaks.ResultsA total of 1,445 interactions of marine mammals and birds with PBRs were observed in the 2,424 hours of video recorded. The 95 marine mammal interactions, 94 by sea otters and one by a sea lion had average durations of three minutes (max 44 min) and represented about 1% of total recording time. The 1,350 bird interactions, primarily coots (Fulica americana) and gulls (Larus occidentalis and L. californicus) had average durations of six minutes (max. 170) and represented 5% of recording time. Interactive behaviors were characterized as passive (feeding, walking, resting, grooming, and social activity) or proactive (biting, pecking, investigating, and unspecified manipulating). Mammal interactions were predominantly proactive, whereas birds were passive. All interactions occurred primarily during the day. Ninety-six percent of otter interactions occurred in winter, whereas 73% of bird interactions in fall, correlating to their abundance in the harbor. Trained pinnipeds followed most commands to bite, drag, and haul-out onto PBRs, made no overt undirected interactions with the PBRs, but showed avoidance behavior to PBR tethers. Instron measurements indicated that sea-otter teeth and gull beaks can penetrate weathered plastic more easily than new plastic.ConclusionsOtter and bird interactions with experimental PBRs were benign. Large-scale OMEGA systems are predicted to have both positive and negative environmental consequences.

Bootstrapping with Models for Count Data

Two methods of bootstrap resampling are discussed with log-linear models for count data. The first involves the resampling of observations and the second involves the resampling of Pearson residuals taking into account changes in the distribution of residuals associated with the expected values of counts. The use of both methods is illustrated on two data sets; one data set concerns the number of ear infections of swimmers related to whether they are frequent swimmers or not and three other variables, and the other data set concerns the number of visits to a doctor made in the last 2 weeks related to the age of subjects and 10 other variables. A third data set on the number of marine mammal interactions in different years and fishing areas is also used as an example. In this case only the second bootstrap method can be used because the nature of the data allows the bootstrap resampling of observations to produce sets of data that could not have occurred in practice. Simulation results indicate that the bootstrap results are slightly better than the results from a conventional analysis for the first data set, and much better than the results from a conventional analysis for the second data set, but a conventional analysis works well for the third data set while there are problems with bootstrap analyses.

Common dolphins subject to fisheries impacts in Southern Australia are genetically differentiated: implications for conservation

AbstractInteractions between short‐beaked common dolphins Delphinus delphis and the fishing industry of South Australia (SA) have lead to serious concerns over the long‐term viability of the local dolphin population. Common dolphins are gregarious animals with high vagility and are expected to display limited genetic differentiation over large spatial scales. Here, we investigate population genetic structure of southern Australian common dolphins using mitochondrial DNA control region sequences and seven microsatellite markers. We found unexpected levels of genetic differentiation for short‐beaked common dolphins over a distance of ∼1500 km. Although no genetic structure was observed in common dolphins along the coast of SA, we detected marked differentiation between dolphins from SA and south‐eastern Tasmania, suggesting a minimum of two genetic populations in southern Australia. We hypothesize that the ephemeral distribution of small pelagic fish enhances movement and dispersal between dolphin groups at a local level. However, clear differences in water temperature, habitat features and fish abundance between SA and Tasmania may contribute to the contemporary isolation observed between dolphin populations. Our findings have important consequences for developing conservation management strategies, because SA has the largest purse‐seine fishery by weight in Australia, and substantial numbers of fatal common dolphin interactions have occurred. In 2004/2005 alone, an estimated 1728 common dolphins were encircled and 377 died over a 7‐month period. If these impacts lead to a reduction in population size, it is unlikely that dolphins from the adjacent south‐eastern Tasmanian population will replace the lost individuals. Recommendations for assessing the impacts of the fishery are presented. The information herein may also have implications for fisheries–marine mammal interactions in coastal and neritic habitats in other areas of the world. Moreover, we demonstrate that a species commonly thought to be wide ranging can show an unexpected degree of genetic differentiation.

Effects of Marine Mammals on the Sport Fishery in Santa Monica Bay, California

Marine mammal-sport fishery interactions in Southern California waters are often observed but far less studied than marine mammal interactions with commercial fisheries (Hanan and Read 1989, Beeson and Hanan 1996, NMFS 1997). Older studies (Fiscus and Baines 1968, Miller et al. 1983) show that sea lions rarely interact with fishing activities in and near Santa Monica Bay while, in later investigations, California sea lions (Zalophus californianus) are reported to negatively affect sport fishing (Beeson and Hanan 1996). Previous to our study, no information was reported on interactions between fishermen and other species of marine mammals, except for Miller et al. (1983). The abundance of marine mammals and sport fishermen makes Santa Monica Bay an excellent area to further investigate marine mammal-sport fishery interactions, to compare results with previous findings, and to provide information for future conservation and management decisions linked with the creation of a Marine Protected Area in Santa Monica Bay. The most common marine mammals known to inhabit and feed in the bay year-round include the California sea lion, the bottlenose dolphin (Tursiops truncatus), the short-beaked common dolphin (Delphinus delphis) and the longbeaked common dolphin (D. capensis) (Bearzi 2005a). A survey of sport fishermen was conducted during 1998–1999 to gather general information on the type of interactions existing between marine mammals and fishermen activities and how marine mammals affect sport fishery in Santa Monica Bay. Of 90 interviewed sport fishermen, 30 were selected for the survey in Marina del Rey and Redondo Beach harbors during February–June 2000. The fishermen selected were required to have fished year-round and to have made at least 20 fishing trips per year in Santa Monica Bay (Point Vicente 33u 459 N 118 249 W to Point Dume 33u 599 N 118 489 W, up to 20 km offshore). Further, the fishermen were chosen from both charter boats (n 5 18) and private vessels (n 5 12); this was different from previous investigations where those interviewed were exclusively on charter boats (Miller et al. 1983, Beeson and Hanan 1996). Information about Sport Fishermen and Their Catches Of the selected fishermen, 87% stated they spent 1–3 days per month fishing in the bay and 80% preferred fishing during the summer months (June–August). Most (67%) fished less than 10 km from shore, of which 43% were within 1–5 km and only one fisherman at less than 1 km from shore. In 1998, 38% of the fishermen reported catching mostly ‘‘bass’’ (the term bass is generally used by local fishermen to include any fish species similar to a rockfish) and 36% reported catching mostly yellowtail, Seriola lalandi. In 1999, 47% of the fishermen reported catching ‘‘bass’’ most abundantly while only 13% reported catching yellowtail. Interactions with Marine Mammals All the fishermen observed dolphins in 1998 and 1999. Virtually all (97%) stated that dolphins – generally recognized as ‘‘common dolphins’’ never interfered with their fishing operations; one fisherman reported one Bull. Southern California Acad. Sci. 106(3), 2007, pp. 215–217 E Southern California Academy of Sciences, 2007

Interactions between small cetaceans and the purse-seine fishery in western Portuguese waters

Marine mammal interactions with Portuguese purse-seine fisheries operating in four different ports (Figueira da Foz, Sesimbra, Setubal, Sines) were studied (July-October 2003). Observers accompanied commercial fishing vessels and monitored 48 fishing trips. An interview survey of skippers was also carried out (n = 36). Three species of marine mammals were observed in 31 sightings during the commercials trips but only the species Delphinus delphis and the category Delphinidae were observed to interact with fishing activities. Small cetaceans were observed to sink, gather or disperse school fishes and damage gear. Mean CPUE and fishing effort values did not change significantly in the presence of dolphins (H = 0.06 and H = 0, both p>0.05). Results from Figueira da Foz indicate that cetaceans are attracted to fishing grounds with a high abundance of their prey-species. Fishermen reported three by-catch events off Figueira da Foz. Compared with other fisheries, purse-seine fishing does not seem to be among the most damaging to marine mammals.

Aquaculture risk management and marine mammal interactions in the Pacific Northwest

This paper reviews current aquatic farm production in the USA and estimates an annual financial exposure of US$350 million in the marine and coastal environments made up of sales, standing crop value and capital investment. In addition, nationwide aquatic farming creates almost 200,000 jobs and, with secondary and downstream activities combined, contributes about US$5600 million to the GNP. The paper then reviews the increasing risk that elements of the coastal aquaculture industry in the Pacific Northwest face from interactions with populations of marine mammals. These are particularly California sea lions and seals, which have greatly increased in the last 20 years from California to British Columbia. Specifically: (i) shellfish from traditional beds have been contaminated by fecal coliforms from seals and made unfit for human consumption, and have been experiencing increasing losses to river otters and sea otters; (ii) culture-based salmon fisheries, including endangered salmon stocks, have been exposed to heavy predation by sea lions and seals, resulting in both direct losses and reduced market value of wounded survivors; (iii) net-pen farms have been exposed to the same heavy losses from predatory sea lions and seals attacking fish in the pens, together with added financial burdens for anti-predator nets, increased maintenance and labor; and (iv) workers in aquaculture and fisheries, and other waterborne industries, have been observing less fear of humans by sea lions and seals, and more direct damage to servicing facilities. The four issues are discussed both technically and economically, and a number of solutions proposed for managing and controlling these increasing risks.