Changing recruitment capacity in global fish stocks

Abstract

Marine fish and invertebrates are shifting their regional and global distributions in response to climate change, but it is unclear whether their productivity is being affected as well. Here we tested for timevarying trends in biological productivity parameters across 262 fish stocks of 127 species in 39 large marine ecosystems and high-seas areas (hereafter LMEs). This global meta-analysis revealed widespread changes in the relationship between spawning stock size and the production of juvenile offspring (recruitment), suggesting fundamental biological change in fish stock productivity at early life stages. Across regions, we estimate that average recruitment capacity has declined at a rate approximately equal to 3% of the historical maximum per decade. However, we observed large variability among stocks and regions; for example, highly negative trends in the North Atlantic contrast with more neutral patterns in the North Pacific. The extent of biological change in each LME was significantly related to observed changes in phytoplankton chlorophyll concentration and the intensity of historical overfishing in that ecosystem. We conclude that both environmental changes and chronic overfishing have already affected the productive capacity of many stocks at the recruitment stage of the life cycle. These results provide a baseline for ecosystem-based fisheries management and may help adjust expectations for future food production from the oceans.fisheries | population dynamics | productivity | recruitment | nonstationary processes H uman well-being is closely linked with the productivity of marine fisheries, which provide a significant source of protein for more than half of the world's population (1). However, ongoing environmental and biological changes may impact productivity through a variety of mechanisms, including larger habitat areas for temperate species (2), altered body sizes (3), food availability (4), and increased exposure to oxygen-depleted and acidic waters (5). Recent research has documented marked changes in the distributional patterns of marine species that are consistent with climate forcing (6, 7). However, the net effect of these changes on global fish stock productivity is not clearly understood. In particular, documented environmental changes (4,8,9) and the long-term consequences of overfishing (10, 11) all impose relevant but poorly constrained effects. Here we help address this issue by evaluating the evidence for empirical trends in the relation between the size of the reproductively mature population (or "spawning stock") and the annual production of juvenile offspring ("recruits") using a recently synthesized global database of stock-recruit time series (12). We then test the relation between empirical recruitment trends and regional environmental variables associated with temperature, phytoplankton abundance, and historical overfishing.Recruitment is modeled by relating the size of the spawning stock biomass to the annual production of recruits. The magnitude of annual recruitment is hi...

The future of fishes and fisheries in the changing oceans

“…While effective reduction and management of fishing effort can rebuild fish stocks to sustainable levels (Worm et al, ; Sumaila et al, ; Costello et al, ), climate change poses fundamental challenge to such measures (Cheung et al, ). Particularly, in addition to the top‐down effect of fishing, bottom‐up environmental factors such as temperature and primary production also play a significant role in determining global fish stock production (McOwen et al, ; Britten et al, ). Bottom‐up environmental factors are changing under climate change, consequently affecting fish stocks and fisheries production.…”

The assessment of fishery status depends on fish habitats

“…However, many well‐managed fish populations are not recovering as expected (Neubauer, Jensen, Hutchings, & Baum, ; Szuwalski & Thorson, ), suggesting other causes have contributed to declines in stock productivity. This contention is supported by evidence that many fish populations are driven by unpredictable regime changes (Vert‐pre, Amoroso, Jensen, & Hilborn, ) and over time, the productivity of many fish stocks has been declining (Britten, Dowd, & Worm, ).…”

Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well

“…fishery | fecundity | zooplankton | lag effect | recruitment T he ultimate combination of factors determining the absence or presence of large classes of recruits entering the fishery is still enigmatic after a century of research (1,2), in particular under climate change (3). The predictive power of useful relationships typically diminishes over time when the blend of influential abiotic and biotic drivers change (4,5).…”

“…Due to the high importance of getting a grip on the expected level of recruitment (REC) for quota decisions, one practical solution is to assume the same REC as in preceding years. Logically, this is a fragile approach as environmental conditions are per definition nonstationary (3). Although fully solving the "recruitment problem" seems unrealistic due to the chaotic nature of the multiple processes involved, the spawning stock biomass (SSB) can be regulated by humans through the degree of fishing intensity.…”