Whiting (Merlangius merlangus) Grows Slower and Smaller in the Adriatic Sea: New Insights from a Comparison of Two Populations with a Time Interval of 30 Years

Abstract

Nowadays, overexploitation and climate change are among the major threats to fish production all over the world. In this study, we focused our attention on the Adriatic Sea (AS), a shallow semi-enclosed sub-basin showing the highest exploitation level and warming trend over the last decades within the Mediterranean Sea. We investigated the life history traits and population dynamics of the cold-water species whiting (Merlangius merlangus, Gadidae) 30 years apart, which is one of the main commercial species in the Northern AS. The AS represents its southern limit of distribution, in accordance with the thermal preference of this cold-water species. Fish samples were collected monthly using a commercial bottom trawl within the periods 1990–1991 and 2020–2021. The historical comparison highlighted a recent reduction in large specimens (>25 cm total length, TL), which was not associated with trunked age structures, therefore indicating a decrease in growth performance over a period of 30 years (L∞90–91 = 29.5 cm TL; L∞20–21 = 22.8 cm TL). The current size at first sexual maturity was achieved within the first year of life, at around 16 cm TL for males and 17 cm TL for females. In the AS, whiting spawns in batches from December to March, showing a reproductive investment (gonadosomatic index) one order of magnitude higher in females than in males. Potential fecundity (F) ranged from 46,144 to 424,298, with it being heavily dependent on fish size. We hypothesize that the decreased growth performance might be related to a metabolic constraint, possibly related to the increased temperature and its consequences. Moreover, considering the detrimental effects of size reduction on reproductive potential, these findings suggest a potential endangerment situation for the long-term maintenance of whiting and cold-related species in the AS, which should be accounted for in setting management strategies.

Adriatic Sea Fishery Product Safety, Prospective and Climate Change

“…This issue is of particular importance for the Adriatic Sea since the impacts of the global warming are particularly critical in semi-enclosed seas (Pozdnyakov et al, 2007). There are already indications that some cold-water fish species, particularly European sprat (Sprattus sprattus) or cold-water species whiting (Merlangius merlangus) are in decline in the last 30 years [16,92].…”

Interannual Variation in the Zooplankton Community of the North Adriatic Sea under Short-Term Climatic Anomalies

“…The large extent of the continental platform and high nutrient input from coastal areas make the Adriatic Sea the most productive basin of the Mediterranean [12]. The cooler area in the north represents a suitable habitat for boreal species like Merlangius merlangus (Linnaeus, 1758), Sprattus sprattus (Linnaeus, 1758), Fucus virsoides (J.Agardh, 1868) and Pseudocalanus elongatus (Brady, 1865) [13,14].…”