Modeling the importance of fish condition, overall health, and disease on the fecundity of White Perch in the Choptank River.

OBJECTIVE: Modeling of fecundity with allometric, nutritional, and environmental covariates has increased sensitivity of reproductive metrics in many fish species. In estuaries with heavy anthropogenic influence, resident species often experience sublethal health impacts because of increased stress, which can include increases in gonadal pathology, intersex, or potential reproductive failure. This study models the fecundity of the estuarine species White Perch Morone americana in response to health parameters identified as signals of habitat stress, including gross pathology presentation, nutritional condition, and disease presence. METHODS: Subpopulation fecundity in the Choptank River (Maryland) of the Chesapeake Bay was estimated using stereological fecundity sampling methods and modeled using information-theoretic approaches of model selection. Nutritional and health parameters identified through health assessment techniques, specific somatic indices, and disease presence were selected as covariates. RESULT: Nutrition demonstrated limited influence on model fit as compared to models with only conventional allometric variables such as weight and length. Of the health variables, gross pathology and somatic indices showed minimal influence on selection, but mycobacterial infection, a chronic condition in the Chesapeake Bay among temperate basses, showed measurable influence. Models with mycobacteriosis included were 40 times more likely the best fit when compared to models with only allometric parameters. CONCLUSION: Whether this has a region-wide influence on all subpopulations will require further research and sampling of the magnitude of mycobacteriosis infection.

Exploring ecosystem-based management in the North Atlantic.

The United States, the EU and Canada established a trilateral working group on the ecosystem approach to ocean health and stressors under the Atlantic Ocean Research Alliance. Recognizing the Atlantic Ocean as a shared resource and responsibility, the working group sought to advance understanding of the Atlantic Ocean and its dynamic systems to improve ocean health, enhance ocean stewardship and promote the sustainable use and management of its resources. This included consideration of multiple ocean-use sectors such as fishing, shipping, tourism and offshore energy. The working group met for 4 years and worked through eight steps that covered the development of common language as a basis for collaboration, challenges of stakeholder engagement, review of the governance mandates, exploring the links between sectors and ecosystems effects, identifying gaps in knowledge and uptake of science, identification of tools for ecosystem-based management, customary best practice for tool development and communication of key research priorities. The key findings were that ecosystem-based management enables new benefits and opportunities, and that we need to make the business case. Further findings were that adequate mandates and effective tools exist for ecosystem-based management, and that ecosystem-based management urgently requires integration of human dimensions, so we must diversify the conversation. In addition, it was found that stakeholders do not see their stake in ecosystem-based management, so greater engagement with stakeholders and targeting of ocean literacy is required and a sustainable future requires a sustained investment in ecosystem-based management, so long-term commitment is key.

Decadal-scale variation in diet forecasts persistently poor breeding under ocean warming in a tropical seabird.

Climate change effects on population dynamics of natural populations are well documented at higher latitudes, where relatively rapid warming illuminates cause-effect relationships, but not in the tropics and especially the marine tropics, where warming has been slow. Here we forecast the indirect effect of ocean warming on a top predator, Nazca boobies in the equatorial Galápagos Islands, where rising water temperature is expected to exceed the upper thermal tolerance of a key prey item in the future, severely reducing its availability within the boobies' foraging envelope. From 1983 to 1997 boobies ate mostly sardines, a densely aggregated, highly nutritious food. From 1997 until the present, flying fish, a lower quality food, replaced sardines. Breeding success under the poor diet fell dramatically, causing the population growth rate to fall below 1, indicating a shrinking population. Population growth may not recover: rapid future warming is predicted around Galápagos, usually exceeding the upper lethal temperature and maximum spawning temperature of sardines within 100 years, displacing them permanently from the boobies' island-constrained foraging range. This provides rare evidence of the effect of ocean warming on a tropical marine vertebrate.

Determination of hematology and plasma chemistry reference intervals for 3 populations of captive Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus).

BACKGROUND: The imperiled status of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), a large, long-lived, anadromous fish found along the Atlantic coast of North America, has prompted efforts at captive propagation for research and stock enhancement. OBJECTIVE: The purpose of this study was to establish hematology and plasma chemistry reference intervals of captive Atlantic sturgeon maintained under different culture conditions. METHODS: Blood specimens were collected from a total of 119 fish at 3 hatcheries: Lamar, PA (n = 36, ages 10-14 years); Chalk Point, MD (n = 40, siblings of Lamar); and Horn Point, Cambridge, MD (n = 43, mixed population from Chesapeake Bay). Reference intervals (using robust techniques), median, mean, and standard deviations were determined for WBC, RBC, thrombocytes, PCV, HGB, MCV, MCH, MCHC, and absolute counts for lymphocytes (L), neutrophils (N), monocytes, and eosinophils. Chemistry analytes included concentrations of total proteins, albumin, glucose, urea, calcium, phosphate, sodium, potassium, chloride, and globulins, AST, CK, and LDH activities, and osmolality. RESULTS: Mean concentrations of total proteins, albumin, and glucose were at or below the analytic range. Statistical comparisons showed significant differences among hatcheries for each remaining plasma chemistry analyte and for PCV, RBC, MCHC, MCH, eosinophil and monocyte counts, and N:L ratio throughout all 3 groups. Therefore, reference intervals were calculated separately for each population. CONCLUSIONS: Reference intervals for fish maintained under differing conditions should be established per population.

Influence of nutritional state on the progression and severity of mycobacteriosis in striped bass Morone saxatilis.

Challenge studies with Mycobacterium marinum clearly demonstrate that a poor diet affects the progression and severity of mycobacteriosis in striped bass Morone saxatilis. Fish (n = 512 total, wt = 65 +/- 15 g) were inoculated intraperitoneally with 10(4) colony-forming units (CFU) g(-1) body weigth (BW) or a physiological saline solution (controls) and evaluated for 8 mo. Inoculated fish fed a low-ration diet (0.15% BW d(-1)) developed a severe, systemic infection characterized by a high bacterial load (>10(8) CFU g(-1) spleen) and poor granuloma formation, which commonly progressed to mortality by 6 wk. In contrast, inoculated fish fed an adequate ration diet (1% BW d(-1)) developed classic granulomatous inflammation of reduced severity and total body energy similar to that found in uninoculated controls (p > 0.05). After 4 wk, fish fed adequate rations maintained an equilibrium state throughout the study period, even though 10(6) CFU g(-1) spleen mycobacteria were consistently cultured. In a second study, reactivation of an acute inflammatory state was demonstrated by placing previously infected fish on reducing diets (0.073% BW d(-1)). In both studies, the energetic demand of this disease was only appreciable when associated with active, severe, inflammatory states. To our knowledge, this study is the first to demonstrate the interaction of diet and mycobacteriosis in fish.

Assessment of costs of reproduction in a pelagic seabird using multistate mark-recapture models.

We used a long-term population band-resight survey database, a parallel reproduction database, and multistate mark-recapture analysis to assess the costs of reproduction, a keystone concept of life-history evolution, in Nazca boobies (Sula granti) from Punta Cevallos, Isla Española, Galápagos, Ecuador. We used eight years of resight and breeding data to compare models that included sex- and state-specific survival probabilities and probabilities of transition between reproductive states using multistate mark-recapture models. Models that included state-specific effects were compared with models lacking such effects to evaluate costs of reproduction. The top model, optimizing the trade-off of model simplicity and fit to the data using the Akaike Information Criterion (AIC), showed evidence of a temporally varying survival cost of reproduction: nonbreeders showed higher annual survival than breeders did in some years. Because increasing investment among breeders showed no negative association with survival and subsequent breeding success, this evidence indicates a cost to both males and females of initiating, but not of continuing, a reproductive attempt. In some cases, breeders reaching the highest reproductive state (fledging an offspring) showed higher survival or subsequent breeding success than did failed breeders, consistent with differences in overall quality that promote both survival and reproduction. Although a male-biased adult sex ratio was observed in this population of Nazca boobies, models of state- and sex-specific survival and transition probabilities were not supported, indicating that males and females do not incur different costs of reproduction, and that the observed sex ratio bias is not due to sex-specific adult mortality.

Nesting distributions of Galápagos boobies (Aves: Sulidae): an apparent case of amensalism.

Blue-footed boobies (Sula nebouxii) in the Galápagos Islands nest at coastal sites such as cliff edges if Nazca boobies (S. granti) are absent. However, if sympatric with nesting Nazca boobies, they nest nearby, but farther inland, in areas with little topographical relief. Nazca boobies nest at the coastal sites whether blue-footed boobies are present or not. The segregated nesting pattern of these two species offers a model system to investigate factors influencing community structure. We tested a non-interactive hypothesis, in which different fundamental niches generate the non-overlapping distributions, and an interactive hypothesis, in which the two fundamental niches overlap and an interaction between the two species causes the segregation. Data on three factors considered as likely parameters differentiating fundamental niches (nest microclimate, nature of the nesting substrate, and ease of taking flight from nest sites) failed to support the non-interactive hypothesis. These results suggest that the two species have indistinguishable fundamental niches with respect to these parameters, but different realized niches. Researchers studying resource partitioning by ecologically similar species often only consider competition (a "-/-" interaction) to explain situations like this, ignoring the more parsimonious amensal (0/-) possibility. Nesting segregation in this situation is apparently caused by attacks of non-breeding adult Nazca boobies on blue-footed booby nestlings, injuring nestlings and ultimately preventing them from fledging. The interaction does not result in any discernible costs or benefits (i.e., effects on fecundity or survival) for the adult Nazca boobies, so it is best described as an amensal interaction. This interaction provides a sufficient explanation of the observed nesting segregation, and precludes present competition for nesting space.